[Federal Register Volume 79, Number 156 (Wednesday, August 13, 2014)]
[Proposed Rules]
[Pages 47521-47545]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-18743]
[[Page 47521]]
Vol. 79
Wednesday,
No. 156
August 13, 2014
Part II
Department of the Interior
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Fish and Wildlife Service
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50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Threatened Status for
the Distinct Population Segment of the North American Wolverine
Occurring in the Contiguous United States; Establishment of a
Nonessential Experimental Population of the North American Wolverine in
Colorado, Wyoming, and New Mexico; Proposed Rule
Federal Register / Vol. 79 , No. 156 / Wednesday, August 13, 2014 /
Proposed Rules
[[Page 47522]]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket Nos. FWS-R6-ES-2012-0107 and FWS-R6-ES-2012-0106; 4500030113]
RIN 1018-AY26; 1018-AZ22
Endangered and Threatened Wildlife and Plants; Threatened Status
for the Distinct Population Segment of the North American Wolverine
Occurring in the Contiguous United States; Establishment of a
Nonessential Experimental Population of the North American Wolverine in
Colorado, Wyoming, and New Mexico
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rules; withdrawal.
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SUMMARY: We, the U.S. Fish and Wildlife Service, withdraw the proposed
rule to list the distinct population segment of the North American
wolverine (Gulo gulo luscus) occurring in the contiguous United States
as a threatened species under the Endangered Species Act of 1973, as
amended (Act). This withdrawal is based on our conclusion that the
factors affecting the DPS as identified in the proposed rule are not as
significant as believed at the time of the proposed rule's publication
(February 4, 2013). We base this conclusion on our analysis of current
and future threat factors. Therefore, we withdraw our proposal to list
the wolverine within the contiguous U.S. as a threatened species. As a
result, we also withdraw our associated proposed rule under section
4(d) of the Act contained in the proposed listing rule and withdraw the
proposed nonessential experimental population designation under section
10(j) of the Act for the southern Rocky Mountains, which published in a
separate document on February 4, 2013.
DATES: The February 4, 2013 (78 FR 7864), proposal to list the distinct
population segment of the North American wolverine occurring in the
contiguous United States as a threatened species and the February 4,
2013 (78 FR 7890), proposal to establish a nonessential experimental
population of the North American wolverine in Colorado, Wyoming, and
New Mexico are withdrawn as of August 13, 2014.
ADDRESSES: The withdrawal of our proposed rules, comments, and
supplementary documents are available on the Internet at http://www.regulations.gov at Docket Nos. FWS-R6-ES-2012-0107 (proposed
listing rule and proposed rule under section 4(d) of the Act) and FWS-
R6-ES-2012-0106 (proposed nonessential experimental population).
Comments and materials received, as well as supporting documentation
used in the preparation of this withdrawal, are also available for
public inspection, by appointment, during normal business hours at:
U.S. Fish and Wildlife Service, Montana Ecological Services Office, 585
Shepard Way, Helena, MT 59601; telephone (406) 449-5225.
FOR FURTHER INFORMATION CONTACT: Jodi Bush, Field Supervisor, U.S. Fish
and Wildlife Service, Montana Ecological Services Office (see
ADDRESSES). Persons who use a telecommunications device for the deaf
(TDD) may call the Federal Information Relay Service (FIRS) at 800-877-
8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish this document. Under the Endangered Species
Act, a species may warrant protection through listing if it is
endangered or threatened throughout all or a significant portion of its
range. Listing a species as an endangered or threatened species can
only be completed by issuing a rule. We issued a proposed rule to list
the distinct population segment (DPS) of the North American wolverine
(Gulo gulo luscus) occurring in the contiguous United States as a
threatened species (78 FR 7864; February 4, 2013), hereafter, referred
to as ``wolverine'' unless otherwise noted. However, this document
withdraws that proposed rule because we have determined that factors
affecting the DPS cited in the proposed listing are not threats to the
DPS such that it meets the definition of an endangered or threatened
species under the Act. Because of our withdrawal of that action, we
also withdraw the associated proposed rule under section 4(d) of the
Act contained in the proposed listing rule (78 FR 7864; February 4,
2013) and withdraw the proposed nonessential experimental population
designation under section 10(j) of the Act for the southern Rocky
Mountains (78 FR 7890; February 4, 2013).
The basis for our action. Under the Endangered Species Act, we can
determine that a species is an endangered or threatened species based
on any of five factors: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence. We have determined that based on new
information and further analysis of the existing and new data, factors
affecting the DPS cited in the proposed listing rule do not place the
wolverine in danger of extinction now or likely to become so in the
foreseeable future.
Peer review and public comment. We sought comments from seven
independent specialists to ensure that our proposed listing
determination was based on scientifically sound data, assumptions, and
analyses. We invited these peer reviewers to comment on our evaluation
of the science underlying our listing proposal. We received substantive
peer reviews from all seven reviewers. We also considered all comments
and information we received during the comment periods. In April 2014,
we convened a panel of experts to provide us with assessments of the
available scientific information on the potential impacts of climate
change on wolverines and their habitat. A report containing the results
of that workshop can be obtained from the Service's Region 6 peer-
review Web site at the following link: http://www.fws.gov/mountain-prairie/science/PeerReviewDocs/Final_Wolverine_Panel_Report.pdf.
That report was made available for public comment through the
Regulations.gov Web site.
Previous Federal Actions
Please refer to the proposed listing rule for the wolverine (78 FR
7864; February 4, 2013) for a detailed description of previous Federal
actions concerning this DPS.
Following publication of the proposed rule, there was scientific
disagreement and debate about the interpretation of the habitat
requirements for wolverines and the available climate change
information used to determine the extent of threats to the DPS.
Differing interpretations of the available climate change information
led to scientific disagreement regarding the current status of the DPS.
In particular, some commenters and peer reviewers raised questions
regarding:
(1) The interpretation of scientific literature in the proposed
rulemaking and scientific literature that may not have been readily
available for our use in our analysis to define habitat parameters.
Specifically, some commenters and peer reviewers questioned the basis
for defining wolverine habitat based on persistent spring snow used by
Copeland et al. (2010). Some peer reviewers and
[[Page 47523]]
commenters suggested that other methods of habitat definition or other
dates used to define habitat based on persistent snow are more
scientifically defensible and would yield very different results.
(2) Commenters suggested that McKelvey et al. (2011) used an
invalid habitat model developed by Copeland et al. (2010) to project
future climate impacts to wolverine habitat, and for that reason, the
commenters believe projections in McKelvey et al. (2011) are also
invalid.
(3) Commenters asserted that there is high uncertainty with
projections made using downscaled global climate modeling, which we
used to analyze the impacts of climate change on wolverine habitat and
ecology.
Based on this substantial disagreement regarding the sufficiency or
accuracy of the available data relevant to the proposed listing, on
February 5, 2014 (79 FR 6874), we announced a 6-month extension of the
final determination of whether to list the wolverine DPS as a
threatened species. We also reopened the comment period on the proposed
rule to list the contiguous U.S. DPS of the North American wolverine
for 90 days.
On April 3-4, 2014, the Service and partners from wildlife agencies
in the States of Idaho, Montana, and Wyoming convened a panel of nine
experts in climate change, wolverines and other mammalian carnivores,
habitat modeling, and population ecology to discuss climate-related
habitat issues and possible future population trends for wolverines.
The objective of this workshop was to better understand the strength of
the relationships between climate change, wolverine habitat, and future
wolverine population trends through dialogue with an expert panel. The
workshop was conducted using a structured agenda with exercises and
discussions to investigate whether and how climate change might affect
wolverines in the contiguous United States. We did not seek consensus
or conformity among panelists, but instead scored panelists' opinions
and elicited discussion regarding the range of variance among expert
opinion. The agenda was divided into four parts: defining wolverine
habitat, evaluating future snow coverage, evaluating future habitat
projections, and evaluating future wolverine population trends. A full
report was generated from the workshop. The report was made available
for public comment through the Regulations.gov Web site and is
available as cited in this withdrawal.
Background
Species Information
Refer to the February 4, 2013, proposed listing rule at 78 FR 7864
for information about the wolverine's taxonomy; life history;
requirements for habitat, space, and food; densities; status in Canada
and Alaska; geographic range delination complexities; distribution; and
habitat relationships and distribution.
Distinct Population Segment
Please refer to our December 14, 2010, 12-month petition finding
(75 FR 78030) and our February 4, 2013, proposed rule to list the North
American wolverine (78 FR 7864) for a detailed evaluation of the
wolverine under our DPS policy.
This Action
Based upon our review of the public comments, comments from other
Federal and State agencies, peer review comments, issues raised by the
wolverine science panel workshop, and other new relevant information
that became available since the publication of our February 4, 2013,
listing proposal, we have determined that the North American DPS of the
wolverine does not warrant listing as an endangered or a threatened
species. This document therefore withdraws the proposed rule published
on February 4, 2013 (78 FR 7864), as well as the associated proposed
rule under section 4(d) of the Act (16 U.S.C. 1531 et seq.) (78 FR
7864; February 4, 2013) and the proposed nonessential experimental
population in Colorado, Wyoming, and New Mexico (78 FR 7890; February
4, 2013).
We have re-analyzed the effects of climate change on the wolverine
under listing factor A (the present or threatened destruction,
modification, or curtailment of the species' habitat or range). While
there is significant evidence that the climate within the larger range
of the wolverine is changing, affecting snow patterns and associated
wolverine habitat, the specific response or sensitivity of wolverines
to these forecasted changes involves considerable uncertainty at this
time (see Summary of Impacts of Climate Changes, below).
We also reevaluated all other risk factors cited in the February 4,
2013, proposed rule, as well as any new potential risk factors that
have come to light since the proposed rule through the public comment
process or new information. We reaffirm our determination in the
proposed rule that these risk factors are not threats to the DPS.
Summary of Comments and Recommendations
The proposed rule published on February 4, 2013 (78 FR 7864),
opened a 90-day comment period on our proposal to list the wolverine as
a threatened species and establish a rule under section 4(d) of the Act
for the subspecies. That comment period closed on May 6, 2013. On
October 31, 2013, we reopened the comment period on the proposed rule
(78 FR 65248) for an additional 30 days, ending December 2, 2013. On
February 5, 2014, we extended our final determination of the proposed
actions for 6 months (79 FR 6874), and at that time we reopened the
comment period for another 90 days, ending May 6, 2014. We also
contacted appropriate Federal and State agencies, scientific experts
and organizations, and other interested parties and invited them to
comment on the proposal. Newspaper notices inviting public comment were
published in newspapers of general circulation in each of the Service
regions within the DPS. We held several public hearings throughout the
range of the DPS; these were held in Boise, Idaho, on March 13, 2013;
in Lakewood, Colorado, on March 19, 2013; and in Helena, Montana, on
March 27, 2013. All substantive information provided during the comment
periods and at the hearings has either been used to support this
withdrawal or is addressed below.
Peer Reviewer Comments
In accordance with our peer review policy published on July 1, 1994
(59 FR 34270), we solicited expert opinion from seven knowledgeable
individuals with scientific expertise that included familiarity with
the wolverine in the contiguous U.S. DPS and its habitat, biological
needs, and threats. We received responses from all seven of the peer
reviewers.
We reviewed all comments received from the peer reviewers for
substantive issues and new information regarding the proposed listing
of the DPS of the North American wolverine. Five peer reviewers
generally concurred with our methods and conclusions and provided
additional information, clarifications, and suggestions to improve the
rule, while two peer reviewers disagreed substantially with the
conclusions in our proposed rule. Peer reviewer comments are addressed
in the following summary and are used to support this withdrawal
document as appropriate.
(1) Comment: Peer reviewers and commenters stated that the
assessment in the proposed rule of the impacts of winter recreation on
wolverines
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understated the potential effect of this risk factor. Commenters stated
that there are significant gaps in our knowledge of the potential
effects of winter recreation on wolverines and recommended more caution
in how we approach the subject.
Our Response: We agree that there is significant uncertainty about
many aspects of wolverine biology and the many potential risk factors
that may affect the species. Our 5-factor analysis considers the best
scientific information currently available. Our determination in the
proposed rule was that the best available information does not indicate
that winter (or summer) recreation is a threat to the DPS. As stated in
the proposed rule, much of the recreational winter use by humans occurs
in relatively small areas, like ski areas, that make up only a small
portion of the large home range of a wolverine, and do not occur at a
scale that is likely to have a population-level effect. We acknowledge
that there are a limited number of studies that have evaluated the
impact of human activities on wolverines (Heinemeyer et al. 2001,
Heinemeyer and Copeland 1999, Heinemeyer et al. 2012, Pulliainen 1968);
however, what information is available indicates there is no threat to
wolverines from recreational activities. This does not mean that new
scientific information, should it show significant impacts from this
factor, would be ignored, or that the case is closed and no more
research is needed. To the contrary, we hope the current research on
the impacts of recreation on wolverines now taking place will shed
significant new light on this issue. Until new data indicate otherwise,
we stand by our assessment that the best available information does not
indicate that winter recreation is a threat to the DPS.
(2) Comment: Multiple reviewers and commenters stated that the
claim in the proposed rule that human-caused mortality is likely
additive to natural mortality is not well-founded, and that under
sufficient scrutiny, it is apparent that human-caused mortality is not
additive in Montana.
Our Response: Very little is known about wolverine populations in
the DPS including population size, trends, mortality, or reproductive
rates. As described in the proposed rule, the population in the DPS is
thought to be around 250-300, and consists of small, semi-isolated
subpopulations that likely interact as a metapopulation with some
connection to the larger population in Canada. It is true that human-
caused mortality has never been demonstrated to be additive or
compensatory in this area. We agree that, given the small amount of
human-caused wolverine mortality and the fact that wolverine
populations are increasing, current levels of mortality are sustainable
and that human-caused mortality is not currently additive. We have
changed this conclusion in this document.
(3) Comment: One peer reviewer stated that the characterization of
the wolverine niche as ``unproductive'' ignores the fact that
wolverines are adapted to exploiting their particular environment. A
niche that is unproductive for most species may be highly productive
for wolverines.
Our Response: Overall, the habitats used by wolverine are
considered unproductive relative to other habitats across the globe.
However, wolverines are specially adapted to take advantage of the
resources offered in the habitats they occupy, and so, the niche is
productive from the wolverine's perspective.
(4) Comment: One peer reviewer and several commenters thought that
the proposed rule states that historical densities would have likely
been higher than today leading to larger historical populations.
Our Response: In the proposed rule, we meant that the overall
population would have been larger historically due to the larger area
occupied by wolverines. We did not mean to suggest that we believed
that densities would have been higher.
(5) Comment: One peer reviewer stated that Aubry et al. (2007) did
not suggest that the habitat in which extralimital records were found
is unimportant and that we incorrectly relayed this in the proposed
rule.
Our Response: We agree with the reviewer that there may be
important areas for wolverines that contain habitat important for
behaviors other than residential home range use or reproduction (for
example, areas of connectivity used for movement between suitable
habitat patches). However, available information on this topic is
lacking, and it is not possible to accurately identify these types of
habitats at this time.
(6) Comment: One peer reviewer commented that lack of adequate gene
flow should be considered a major threat to wolverines. The potential
for human occupation of linkage habitat could adversely affect movement
of wolverines between habitats, making gene flow a more important issue
in the future.
Our Response: We agree that it is possible that lack of sufficient
connectivity between populations and resultant lack of genetic exchange
could affect wolverines. However, at this time, the best available
information does not suggest that lack of adequate gene flow or reduced
genetic diversity has had negative effects on wolverines in the DPS, as
is discussed below. Human disturbance in wolverine habitat in the
contiguous United States has likely resulted in the loss of some minor
amount of wolverine habitat, but this loss has not yet been quantified.
Wolverines have been documented to persist and reproduce in areas with
high levels of human use and disturbance, including developed alpine
ski areas and areas with motorized use of snowmobiles (Heinenmeyer
2012, entire), which suggests that that such activities are not likely
to impede movement of wolverines between habitats. Whether human
occupation or disturbance reduces wolverine gene flow, and ultimately
wolverine population or metapopulation persistence, is uncertain at
this time.
(7) Comment: Several peer reviewers and commenters thought that
climate change is likely to have the effect of concentrating human
activities, like winter recreation, into remaining cold, snowy habitat,
further increasing the effect of these activities on wolverines.
Our Response: This scenario, while possible, is speculative. It is
also possible (but similarly speculative) that winter recreation will
become less popular as opportunities diminish. However, we have no
evidence to suggest that winter recreation activities have a negative
effect on wolverines;, and whether further concentrating recreation
into smaller areas (should this occur) would affect wolverine
population and metapopulation persistence is uncertain. These potential
effects were considered but do not rise to the level of a threat
because available information does not indicate evidence of such
effects at this time.
(8) Comment: One peer reviewer and several commenters stated that a
population viability analysis would provide better information on which
to base the listing decision than what is currently relied upon.
Our Response: While a population viability analysis may be
desirable, at this point in time, none exists for wolverines in the DPS
due to a lack of demographic information that would be required to do
such an analysis. The Act requires that we base the listing decision on
the best scientific and commercial information available at the time of
the decision.
(9) Comment: One peer reviewer and many commenters asserted that
loss of genetic diversity due to small population size is a threat to
the DPS regardless of climate change.
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Our Response: Small population size and reduced genetic diversity
are potential, though as-yet undocumented, threats to wolverines in the
contiguous United States. There is some evidence that genetic diversity
is lower in wolverines in the DPS than it is in the more contiguous
habitat in Canada and Alaska. The consequence of this lower genetic
diversity to wolverine conservation is unknown. We do not discount the
possibility that loss of genetic diversity could be negatively
affecting wolverines now and continue to do so in the future. It is
important to point out, however, that wolverine populations in the DPS
area are thought to be the result of colonization events that have
occurred since the 1930s. Such recent colonizations by relatively few
individuals and subsequent population growth are likely to have
resulted in founder effects, which could contribute to low genetic
diversity (Schwartz et al. 2007). While we acknowledge that the effect
of small population size and low genetic diversity may become more
significant if populations become smaller and more isolated, we lack
reliable information to conclude if and when this would occur.
(10) Comment: One peer reviewer stated that the proposed rule
should not have considered trapping a threat because trapping only
occurs in Montana, and to be considered a threat, an activity must
occur across the entire range of the DPS.
Our Response: In a listing analysis, we consider all potential
threats regardless of the extent of their occurrence to make a
determination as to whether all of the threats, when considered
individually or cumulatively, indicate that the DPS meets the
definition of an endangered or threatened species under the Act.
Therefore, threats that occur in only a portion of the range of the DPS
may affect the conservation status of the whole, or affect a
substantial enough portion of the whole so that the future of all or a
significant portion of the range of the DPS is at risk.
(11) Comment: The conclusion that females are unlikely to move into
the southern Rocky Mountains on their own is speculative.
Our Response: Although most studies document greater dispersal
distances for males than females (Hornocker and Hash 1981, p. 1298;
Banci 1994, pp. 117-118; Copeland and Yates 2006, Figure 9; Moriarty et
al. 2009, entire; Inman et al. 2009, pp. 22-28; Brian 2010, p. 3;),
Vangen et al. (2001, p. 1644) found that both males and females are
capable of long-distance dispersal. They documented female dispersal
distances of up to 178 km in one case, with average dispersal distance
(60 48 km) not significantly different from males (51
30 km). Given this scientific evidence, we believe it is
possible that females could move into the southern Rocky Mountains
without human facilitation.
(12) Comment: One peer reviewer commented that the proposed rule
indicates that we have strong information about where wolverine dens
occur in Idaho and Montana. This may lead the reader to believe that
all potential denning areas are known. This is not the case.
Our Response: We agree with the reviewer that we do not know where
all potential wolverine dens are located. Dens may occur outside of the
conditions described in the proposed rule. Although the proposed rule
provided an accurate summary of the existing scientific information
pertaining to documented den sites in Idaho and Montana, we did not
mean to imply that all potential denning sites are known.
(13) Comment: One peer reviewer noted that, in the proposed rule,
we indicate that the elevations used by wolverines that once inhabited
the Sierra Nevada Range are unknown. In fact, we do have reliable
information that is compiled in Aubry et al. 2007.
Our Response: While we agree that the account of location data in
Aubry et al. (2007) provides some information on wolverine use of the
Sierra Nevada Range, the information contained in that report is not
comparable to habitat use information from radio-telemetry studies used
elsewhere in the proposed rule, where we reported highly credible
elevation information (Copeland 1996, p. 94; Magoun and Copeland 1998,
pp. 1315-1316; Inman et al. 2007c, p. 71). The information reported in
Aubry et al. (2007) represents opportunistically collected wolverine
encounters and trapping information, which are likely biased by factors
that affect the probability of humans detecting wolverines. These
biases include the confounding factor of human use and baiting of
traps, which could cause wolverines to venture into habitats they
otherwise seldom use. These potential biases led us to conclude that
the elevation data for California compiled by Aubry et al. (2007) are
not reliable for drawing conclusions regarding wolverine habitat use in
the Sierra Nevada at any but the grossest of scales.
(14) Comment: One peer reviewer stated that the proposed rule was
premature in concluding that the Great Lakes and Northeast regions do
not support a wolverine population now, and likely did not support
wolverine populations historically. This conclusion is not well
supported by the available information, which shows a relatively
consistent historical record for the early post-settlement period for
the Great Lakes and a sparser record for the Northeast.
Our Response: Our conclusion that the Great Lakes area was not
historically wolverine habitat was based on a review of historical
occurrence records for wolverines in this area. We agree that the
conclusion about historical populations was premature, and that this
area may have supported wolverine populations prior to and into the
settlement period. We continue to conclude that the Northeast was
unlikely to have supported wolverines historically, but agree that the
evidence is not definitive.
(15) Comment: One peer reviewer asserted that the proposed rule
erred by stating that wolverines are habitat generalists. Wolverines
require very specific habitat conditions and are correctly considered
habitat specialists.
Our Response: Wolverine habitat in the contiguous U.S. appears to
consist of disjunt patches of rugged, high alpine areas with with a mix
of tree cover, alpine meadow boulders, avalanche chutes, and patches of
spring snow (Copeland et al.2010, entire; Inman et al. 2012, p.785;
Inman et al. 2013, p. 283). We agree that they could be considered
habitat specialists.
(16) Comment: One peer reviewer noted that the proposed rule
indicates that the wolverine found in the Sierra Nevada Range of
California in 2008 was from Idaho based on genetic information. The
genetics of that individual were not diagnostic of Idaho, and could in
fact have come from other portions of the wolverine range.
Our Response: Moriarty et al. (2009, entire) used mitochondrial and
microsatellite genetic evidence, as well as stable isotope analysis, to
verify the wolverine's origin. That analysis placed the California
wolverine into a group primarily comprised of individuals from the
Sawtooth Mountains of Idaho with a confidence level of 73.4 percent.
(17) Comment: Several peer reviewers and commenters were confused
by our use of wolverine science from Scandinavia or were unsure when
our conclusions were based on Scandinavian data.
Our Response: We have attempted to clarify when referring to data
collected in Scandinavia. In many cases when we do not have data from
North America, we found Scandinavian wolverine data are the best
available information regarding general wolverine biology,
[[Page 47526]]
where behavior is consistent regardless of geographic region.
(18) Comment: One peer reviewer commented that there are historical
wolverine records from New Mexico, and this should be noted in the
rule.
Our Response: The potential for wolverine presence in New Mexico is
confounded by a sparse historical record that may not accurately
reflect wolverine distribution. One 19th century record from New
Mexico--without precise locality information--was reported in Aubry et
al. (2007). The lack of precise location data in this area so close to
Colorado and its known historical (pre-1930) wolverine population
leaves open the possibility that the animal in question was actually
from the mountains of adjacent Colorado. Habitat in the Sangre de
Cristo Mountains of northern New Mexico is contiguous with habitat in
Colorado that contained verifiable historical wolverine records. Based
on this evidence of contiguous habitat and a documented record, it is
likely (though uncertain) that wolverines in the southern Rocky
Mountains occurred in adjacent contiguous habitat in New Mexico's
Sangre de Cristo Mountains and possibly other mountain ranges in
northern New Mexico. It is not known whether wolverines in this area,
if present, would have been established as an extension of the southern
Rocky Mountain population, or rather might have been occasional
migrants to the area.
(19) Comment: One peer reviewer commented that the proposed rule
determined that the DPS is discrete based on the international boundary
between the United States and Canada. The reviewer suggested that the
Service could also conclude the DPS is discrete based on differences in
genetics between the populations in Canada and the United States.
Our Response: As described in our December 14, 2010, 12-month
petition finding (75 FR 78030) and our February 4, 2013, proposed rule
to list the DPS (78 FR 7864), to be considered discrete under our DPS
Policy, a population of a vertebrate species needs to satisfy either of
two conditions: (1) It is markedly separated from other populations of
the same taxon as a consequence of physical, physiological, ecological,
or behavioral factors (measures of genetic or morphological
discontinuity may provide evidence of this separation); or (2) it is
delimited by international governmental boundaries, across which
differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist. Having found that
the population was discrete based on the differences in control of
exploitation and conservation status across the international boundary,
an evaluation of possible genetic discontinuity was not necessary, as
only one of the conditions need be met to satisfy the discreteness
criterion.
(20) Comment: One peer reviewer and several commenters said that
climate changes to ecosystems can cause counter-intuitive movement of
climatic conditions, resulting in changes that are difficult to
predict. For example, in the proposed rule it states that wolverine
habitat is likely to migrate northward and up mountain slopes as
climate changes progress, but this result is not necessarily the case.
Our Response: We agree that there is considerable uncertainty in
how climate change will affect wolverine habitat and population
persistence. Climate modelling has been done at broad ecological
scales, and we do not know how fine-scale changes in snow patterns may
affect population viability. There are a variety of fine-scale local
factors that determine where wolverines den, the quality of den sites,
and how wolverines use the landscape. As is discussed further below, we
lack a clear understanding of how changes in snowfall will affect
wolverine habitat quality and ultimately population viability and
persistence, and that is reflected in the text of this document.
(21) Comment: Two peer reviewers and multiple commenters stated
that the proposed rule relies almost entirely on the Copeland et al.
(2010) bioclimatic envelope model as a prediction of suitable habitat.
This hypothesis is not based on sound theory.
Our Response: While Copeland et al. (2010) portrays a strong
argument for wolverine reliance on spring snow cover, their modeling
did not consider other factors such as land cover, topography, and
human footprint that have been considered in the analyses by Inman et
al. (2013) and Fisher et al. (2013). Further, Copeland himself
(November 26, 2013; p. 2) stated his belief that there are other
factors beyond snow that influence wolverine distribution. We have
reflected these concerns in the text of this document.
(22) Comment: One peer reviewer commented that the model in
Copeland et al. (2010) overestimates the habitat used for wolverine
denning by approximately 75 percent. This means that up to 75 percent
of that modeled habitat could be lost to climate change impacts without
affecting wolverine populations. Therefore, the predicted impacts of
the McKelvey et al. (2011) analysis are not likely to occur.
Our Response: It is unclear how much habitat wolverines need for
denning purposes. However, den sites do not appear to be limited at
this time. Available information suggests it is possible that changes
in climate may affect availability of deep snow for den sites, but the
specific response or sensitivity of wolverines to these forecasted
changes is uncertain at this time.
(23) Comment: Two peer reviewers asserted that effective population
estimates cited in the proposed rule from Schwartz et al. (2009) did
not include sampling from portions of the range of the DPS. This lack
of sampling the entire DPS area may have biased the estimated effective
population size low.
Our Response: The reasons for excluding areas from the sample are
covered in Schwartz et al. (2009) and have to do with reducing the
effects of population substructure in the effective population size
estimate. Essentially, when making this type of calculation, one
attempts to sample those animals that are part of an interbreeding
population. It is not desirable to include adjacent populations that
may be semi-isolated, as this would bias the results. The purpose of
estimating genetically effective population size is not to produce a
population estimate, but to use the effective population size estimate
as a tool to make inferences about the potential for the maintenance of
genetic diversity. In that light, it is appropriate to sample only from
areas that are thought to form cohesive populations. The estimate
provided for the northern Rocky Mountains populations was low, and
represents the effective population size for that area. This result is
important to the listing decision because the northern Rocky Mountains
portion of the DPS is thought to be the largest subpopulation in the
DPS and is physically connected to Canada. Therefore, we expect that
the northern Rocky Mountains would have the subpopulation that is most
genetically resilient of the current subpopulations in the DPS.
(24) Comment: One peer reviewer commented that the bioclimatic
envelope model in Copeland et al. (2010) does not encompass all habitat
and all dens used by wolverines, and so is invalid.
Our Response: Copeland et al. (2010) acknowledge that information
on wolverine historical range in Europe and Asia is lacking and the
``Methods'' section of their paper describes the timeframe and other
criteria used as a basis for the habitat and den site information used
in their modeling. Models typically do not encomass all
[[Page 47527]]
habitat and reproductive areas used by the particular species being
assessed. The validity of models and their outcomes does not require
that they encompass all habitat and all reproductive areas of a
species. While we find that the model does provide valuable information
on the correlation between wolverine and snow cover, we acknowledge
that there are limitations.
(25) Comment: Two peer reviewers and several commenters stated that
central to acceptance of the Copeland et al. (2010) snow model and the
subsequent use of the snow model in McKelvey et al. (2011) for
predicting future wolverine habitat in the western States, one must
accept that wolverine denning extends to May 15 and that continuous
snow cover is required until then in the western States.
Our Response: The habitat described in the Copeland model includes
areas that retained snow until May 15, in as few as 1 of 7 years. In
other words, if an area retained snow in only 1 of 7 years, it was
still included in the model describing habitat, and 97.9 percent of the
sample of den sites fell within this area. That means that some
proportion of those den sites fell within an area that did not retain
snow each year. We acknowledge that den abandonment often occurs
earlier than May 15. Abandonment varies from March to May, with earlier
timing associated with den sites in Idaho, and later abandonment
documented in Alaska and Norway (Myrberget 1968, pp. 112-114; Magoun
and Copeland 1998, pp. 1316-1317). However, 95 percent of summer and 86
percent of winter telemetry locations were concordant with spring snow
coverage. It is important to note that factors beyond spring snow
persistence were not considered in the model; therefore, the model may
not present a complete picture of factors that influence wolverine
distribution.
(26) Comment: Two peer reviewers and several commenters thought
that the results in Copeland et al. (2010) are biased by the fact that
most known wolverine dens occur in mountainous habitats. This is an
artifact of where people have searched for wolverine dens rather than
where most dens occur. If more searching had been done in lowland
boreal habitats, the fit of the Copeland et al. (2010) model would not
have been as good.
Our Response: It may be true that if more dens had been discovered
in flat or lowland boreal forest areas that the fit of the model would
have been worse. This is explained by the authors of Copeland et al.
(2010) as an artifact of the remote sensing data used in the analysis.
Heavily canopied habitats, such as lowland boreal forests, hide snow
beneath canopy cover, and the snow may be missed by satellites. This
problem is largely irrelevant to the listing determination, however,
because the habitats in the contiguous U.S. DPS are not lowland boreal
habitats but rather mountainous habitats where the model fit is very
good.
(27) Comment: Two peer reviewers and several commenters said that
the analysis in Copeland et al. (2010) is invalid as an estimate of
wolverine habitat. McKelvey et al. (2011) relies on Copeland et al. for
input data, and so is also invalid as an estimate of the potential
impacts of climate change on wolverine habitat.
Our Response: Copeland et al. (2010) portrays a strong argument for
wolverine reliance on spring snow cover; however, as discussed under
Factor A, the analysis did not consider factors beyond snow that may
influence wolverine habitat. Therefore, we believe that while Copeland
et al. (2010) represents the best available information, the model
outcome may not provide a complete picture of available habitat. In
their climate change modeling, McKelvey et al. (2011) relied on
conclusions in Copeland et al. (2010), that wolverine habitat is
closely tied to persistent spring snow cover. Given the uncertainties
in Copeland et al.'s (2010) bioclimatic envelope model, predictions of
wolverine habitat under climate change in McKelvey et al. (2011) may
also not be accurate.
(28) Comment: Two peer reviewers stated that the limitations of
Moderate Resolution Imaging Spectroradiometer (MODIS)-based snow cover
models should be recognized and taken into consideration when
evaluating the accuracy of snow model predictions. For example,
McKelvey et al. (2011) recognized that there are issues with the scale
at which the MODIS data can be applied.
Our Response: We agree that there are limitations inherent in
downscaled climate models and that it is important to understand the
effect of climate-data spatial resolution on wolverine viability in
complex terrain. Downscaling techniques improve understanding of
climate at smaller, regional scales compared to Global Climate Models,
but their spatial resolution is still inadequate to describe the
variability of microclimates in which organisms live (Potter et al.
2013, p. 2935). Franklin et al. (2012, pp. 478-482) show that there can
be large differences between suitable habitats predicted from coarse
versus fine-scale climate models, and concluded that, on average, a
scale approximately twice as fine as that used in McKelvey et al.
(2011, entire) (280 m vs. 500 m) is adequate, and that in rugged
terrain (such as that used by wolverines), even finer models (e.g., 10
to 30 m) may be needed to represent significant microclimates. McKelvey
et al. (2011, p. 2895) reached similar conclusions about their own
modeling efforts: ``although wolverine distribution is closely tied to
persistent spring snow cover (Copeland et al. 2010), we do not know how
fine scale changes in snow patterns within wolverine home range may
affect population persistence.'' We concur; an improved understanding
of how microclimatic variation alters the habitat associations of
wolverines at fine spatial scales is needed. Ultimately, our final
listing decision for the wolverine rested on the question of whether we
can reliably predict how the effects of changes in climate on habitat
may affect population persistence in the DPS; therefore, this
limitation of the model was of critical importance in our reevaluation
of the proposed rule.
Comments From States, Agencies, and the Public
(29) Comment: There is not enough information known about the
wolverine population, such as size, demographics, distribution, and
trend, on which to base a listing rule.
Our Response: We are required to use the best available scientific
and commercial information when listing a species under the Act.
Published findings on wolverine populations and their genetic structure
has been available for many years, although we acknowledge that
information on wolverine numbers, population trends, and potential
effects of loss of genetic diversity is limited. Our analysis included
a thorough consideration of all available literature, peer review,
public comment, and results of a scientific panel (Service 2014,
entire). Based on our analysis, through this document, we withdraw the
proposed rule to list the DPS of the North American wolverine occurring
in the contiguous United States as a threatened species under the Act
(78 FR 7864; February 4, 2013), as well as our associated proposed rule
under section 4(d) of the Act contained in the proposed listing rule
(78 FR 7864; February 4, 2013) and the proposed nonessential
experimental population designation for the southern Rocky Mountains
(78 FR 7890; February 4, 2013).
(30) Comment: Several commenters stated that the global climate
models used to predict habitat impacts of climate change are not
precise enough to be useful for that purpose.
[[Page 47528]]
Our Response: We have carefully reexamined all of the best
available scientific data used in our proposed rule, and any
information that has became available through the review process since
the publication of the proposed rule. As explained in detail in this
document, we concluded that the analyses in McKelvey et al. (2011) and
other sources were not conducted at a fine enough scale to serve as the
basis for having sufficient certainty about how climate change may
impact wolverine habitat in the future. In addition, we have recognized
substantial uncertainty exists regarding projections of future snowfall
amounts and persistence in areas most important for crucial wolverine
life stages (i.e., denning), and as well as the possible response of
the DPS to effects of climate change in the future.
(31) Comment: There are alternative hypotheses to explain the
distribution of wolverines that should be explored further.
Our Response: We agree that it is important to consider all
potential factors that may constrain wolverine distribution. The
Copeland et al. (2010) model focused on one hypothesis, spring snow
persistence, to explain wolverine distribution. The model did not
consider other factors such as land cover, topography, and the human
footprint that appear to also influence primary wolverine habitat use
(Inman et al. 2013; Fisher et al. 2013). Copeland himself (November 26,
2013; p. 2) stated his belief that there are other factors beyond snow
that influence wolverine distribution. These considerations were part
of the basis for our decision to withdraw the listing rule.
(32) Comment: One commenter questioned the evidence for the
assumption in the proposed rule that predation is part of the reason
for wolverines denning in deep snow.
Our Response: Predation as an explanation for wolverines denning in
deep snow has been suggested by several wolverine experts, including
Magoun and Copeland (1998), Copeland et al. (2010), and Inman et al.
(2012, p. 638).Wolverine kits are vulnerable to predation by other
wolverines and other predators while they are in the den (Persson et
al. 2003, p. 24). Female wolverines often dig elaborate snow tunnels
down to ground-level substructure, such as boulders or avalanche
debris, to birth and raise kits. A reasonable explanation as to why
they go to this effort is that kits need security from predators that
such snow tunnels provide.
(33) Comment: Several commenters asserted that the proposed rule
relies on inadequate science regarding genetic connectivity and
effective population sizes in wolverines. They also claim that the
proposed rule is inconsistent in applying genetic information to
designating the DPS and the discussion of effective population size.
Our Response: We are required to use the best available scientific
and commercial information when determining whether to list a species
under the Act. We have found in this determination that genetic factors
are not a threat to the DPS due to increasing populations. Although we
did not use the lack of genetic contiguity between Canada and the
United States wolverine population as justification for the DPS, we do
recognize the apparent lack of gene flow across the international
boundary.
(34) Comment: Several commenters said that because wolverines have
persisted through past climate changes that were severe, they will
persist through future changes as well.
Our Response: While we acknowledge that the wolverine and other
species have persisted through past changes in climate, it does not
automatically follow that the wolverine or other species will persist
through future changes since the conditions concerning the status of
the species, its habitat, and other relevant factors and their
responses to such changes are unlikely to be identical to what was
present in the past. In our analysis of the best available data
concerning the wolverine DPS, there is significant evidence that the
climate within the larger range of the wolverine is warming, affecting
snow patterns and associated wolverine habitat. However, as described
in this document, we currently have a relatively high degree of
uncertainty about the likely response of wolverines to future changes.
(35) Comment: The Service should monitor wolverine populations and
habitat to determine if climate change impacts actually occur before
pursuing a listing based on a speculative threat.
Our Response: The Act requires that we make a listing determination
based on the best scientific and commercial data available at the time
of our decision. When evaluating population trends or the impacts of a
particular threat, we must rely on the best available science, rather
than speculation, to assess the future status of a species and to
determine whether it meets the definition of an endangered or
threatened species. As explained above, we have determined that the
best available information suggests that climate change may affect
habitats used by wolverines; however, the specific response or
sensitivity of wolverines to these current and forecasted changes is
uncertain at this time.
(36) Comment: Management of wolverines is similar in Canada and the
United States. There is no reason to conclude that wolverines in these
areas are discrete based on differences in management.
Our Response: Wolverines are managed by regulated harvest
throughout western Canada and Alaska; in the lower 48 U.S. States,
regulated wolverine harvest occurs only in Montana, and at a very low
level (average harvest = 3.25 wolverines/year; Montana Department of
Fish Wildlife and Parks 2010, pp. 8-11). In November 2012, a district
court issued a restraining order blocking the opening of Montana's
trapping season on wolverine; the season remains closed (Case No. BDV-
2012-868). Thus, we conclude there are differences in management across
the international boundary. Please refer to our December 14, 2010, 12-
month petition finding (75 FR 78030) and our February 4, 2013, proposed
rule to list the DPS (78 FR 7864) for a more robust discussion of our
analysis of wolverine in the contiguous United States and our DPS
Policy. However, as described in this document, we have concluded that
this DPS does not warrant listing, and we are withdrawing our February
4, 2013, proposed rule to list the DPS of the North American wolverine
occurring in the contiguous United States as a threatened species under
the Act (78 FR 7864; February 4, 2013), as well as our associated
proposed rule under section 4(d) of the Act contained in the proposed
listing rule (78 FR 7864; February 4, 2013) and the proposed
nonessential population designation for the southern Rocky Mountains
(78 FR 7890; February 4, 2013).
(37) Comment: Several commenters noted that regulatory mechanisms
to combat climate change do not exist; therefore, it is not appropriate
to use this threat to justify a listing.
Our Response: Under the Act, regardless of whether regulatory
mechanisms exist to address a particular threat, we cannot ignore that
threat if it contributes to the basis for a determination that the
species meets the Act's definition of an endangered or threatened
species. As a hypothetical example, if a severe disease is placing a
species at high risk of extinction and no regulatory mechanisms exist
to combat the disease, we would not ignore the disease as part of the
basis for a listing determination. Also, with regard to climate change,
we consider the ongoing and reasonably likely effects of such changes
and how those
[[Page 47529]]
effects relate to the status of a species; we do not make listing
determinations based on climate change per se. For example, our
decision to list the polar bear was based on the likely loss of sea ice
habitat and related impacts to polar bears. While it may seem like a
fine point that we focus on the effects of changes in climate rather
than climate change per se, it is an important distinction. With regard
to the wolverine DPS, we have determined that potential habitat impacts
due to climate change are not a threat to the DPS such that the species
meets the definition of an endangered or threatened species under the
Act at this time. Therefore, an analysis of the existing regulatory
mechanisms that address the effects of climate change is not necessary
in this case.
(38) Comment: Multiple commenters noted that there are several
datasets available that Copeland et al. (2010) did not consider and
that including those in the analysis would likely change the outcome of
our proposed rule.
Our Response: We acknowledge that some available datasets were left
out of the Copeland et al. (2010) model. The authors also acknowledge
that information on wolverine historical range in Europe and Asia is
lacking. While we believe the model does provide valuable information
on the correlation between wolverine and snow cover, these omissions
limit the ability to provide a complete picture of available wolverine
habitat. We incorporated a discussion of these limitations of the
dataset into the text of this document.
(39) Comment: Several States commented that the analysis in
Copeland et al. (2010) excluded data from wolverines in the far north
for their year-round analysis of habitat use relative to their snow
model. If they had included these animals from places where persistent
spring snow was ubiquitous they would have found that they did not
select for snow.
Our Response: The Copeland et al. (2010) paper addressed this
issue, saying that in areas of the far north in arctic and sub-arctic
conditions, wolverines are able to use the entire landscape and that
therefore their model loses effectiveness for predicting wolverine
habitat use. This is not an issue in the contiguous U.S., where
wolverine habitat occurs at high elevations in temperate mountains. In
these areas, the correlation between the bioclimatic envelope and
wolverine habitat use and denning is quite close.
(40) Comment: Several States and commenters asserted that
wolverines do not need deep snow until May 15 for thermal buffering
because temperatures have moderated by then.
Our Response: We agree. We do not know exactly what the causal
relationship is between spring snow and wolverine dens. Thermal
buffering is a hypothesis, but has not yet been tested. Additionally,
as mentioned above, the timing of den abandonment varies geographically
and seems to coincide with spring thaw. Wolverines in Idaho appear to
abandon den sites earlier (March-April) than in other areas studied,
including Alaska and Norway (late April-early May). It appears possible
that wolverines in the DPS area do not need snow until May 15.
(41) Comment: One State commented that climate change may benefit
wolverines due to increased productivity in their habitats.
Our Response: Although this hypothesis could possibly be true, the
best available information does not support or refute this hypothesis.
Our withdrawal of the proposed listing rule is based upon the lack of
information concerning the likely biological response of wolverines to
the effects of climate change. We do not assert that wolverines are
likely to benefit from climate change or its effects on habitat.
(42) Comment: Several States commented that wolverines have
expanded their populations in the DPS over the last 100 years.
Simultaneous to this expansion, climate warming has also been reducing
snowpack in the DPS. This is inconsistent with the hypothesis that
persistent spring snow is important to wolverines or that changes in
persistent spring snow in the future are likely to adversely affect
wolverines.
Our Response: Wolverines were likely extirpated from the entire
contiguous United States in the first half of the 20th century due to
unregulated trapping and predator control; populations have since
recolonized from Canada and are currently expanding within the DPS area
(refer to the on February 4, 2013 proposed rule at 78 FR 7864 for a
more robust discussion of wolverine population status and
distribution). We believe this recolonization and expansion is
primarily due to changes in harvest and predator control practices. The
best available information does not indicate that climate change
effects have caused contraction of wolverine habitat in the DPS area at
this time, and consequently wolverine growth and expansion has not
ceased. It is likely that climate change will impact snowfall and snow
persistence in the future, but we have no reliable information to
suggest how wolverines in the DPS will respond to these changes.
(43) Comment: One State disagreed with our determination in the
proposed rule that wolverine genetic variation is low, or lower than
historical levels, in the northern Rocky Mountain wolverine population.
Our Response: Available evidence indicates that genetic diversity
among wolverines in the DPS is lower than it is in the founding
population in Canada (Schwartz et al. 2009, p. 3229). Wolverines in the
contiguous United States are thought to be derived from a recent
recolonization event after they were extirpated from the area in the
early 20th century (Aubry et al. 2007, Table 1). Consequently,
wolverine populations in the contiguous United States have reduced
genetic diversity relative to larger Canadian populations as a result
of founder effects or inbreeding (Schwartz et al. 2009, pp. 3228-3230).
Such a result is not unexpected following recolonization by relatively
few individuals and subsequent population growth. Whether the DPS may
be suffering any negative effects as a consequence of lower genetic
diversity in comparison to the Canadian population is unknown. While we
acknowledge that the effect of small population size and low genetic
diversity may become more significant if populations become smaller and
more isolated, we are uncertain if and when this response might occur.
(44) Comment: Several States commented that there is insufficient
evidence to conclude that there is a genetic break between the DPS and
Canadian populations. Insufficient sampling in the area near the
international boundary means that the precise location of any break
that may exist is in question.
Our Response: We reviewed the best available information on this
subject. States did not provide additional citations. The analysis in
Schwartz et al. (2009) provided evidence that there is a lack of
genetic connectivity between wolverine populations in the area near the
international boundary. The reason for the apparent lack of
connectivity is not known. The authors speculated that it may be
related to heavy trapping pressure on the Canadian side of the
boundary, but this hypothesis remains untested.
(45) Comment: Several commenters stated that hunting and trapping
of species that prey on wolverines would benefit the DPS.
Our Response: It is possible that hunting and trapping benefit
wolverines by reducing populations of predators that may occasionally
kill wolverines.
[[Page 47530]]
The magnitude of this potential benefit, if it exists, is unknown.
(46) Comment: Multiple commenters and States thought that the
listing proposal essentially dismissed habitat impacts resulting from
land management decisions.
Our Response: The Service recognized and acknowledged the effects
of land management activities, as well as recreation, infrastructure,
and development, on the wolverine DPS. However, as we stated in the
proposed listing rule, the scale at which these activities occur is
relatively small compared to the average size of a wolverine's home
range. For that reason, we concluded that land management decisions do
not substantially impact the wolverine. After reviewing the best
available information, we stand by this assessment.
(47) Comment: One commenter believed the wolverine does not qualify
as a DPS because the population is not discrete, and loss of the
subspecies in the contiguous United States would not represent a
significant gap in relation to its entire range, which includes areas
within the contiguous United States, Canada, and Alaska. The population
and habitat area in the lower 48 States represent a small fraction of
the entire range; meaning that, for the purposes of the Act, the
wolverine is insignificant when compared to the entire North American
subspecies.
Our Response: Please refer to our December 14, 2010, 12-month
petition finding (75 FR 78030) and our February 4, 2013, proposed rule
to list the North American wolverine (78 FR 7864) for a more robust
discussion of our analysis of the wolverine in the contiguous United
States and our DPS policy. We recognize that there may be differences
of opinion on the definition of ``significant.'' However, for the
reasons detailed in the February 4, 2013, proposed rule, we conclude
both that the contiguous U.S. population of the wolverine is discrete
and that the loss of that population would result a significant gap in
the range of the taxon, in accordance with our DPS policy. However, as
described in this document, we have concluded that this DPS does not
warrant listing, and we are withdrawing our proposed rule to list the
DPS.
(48) Comment: Several States commented that the determination that
the wolverine population in the contiguous United States is discrete is
arbitrary and without merit because the only regulatory mechanism that
the Service concludes is lacking is one that exists internationally,
that is, the current inability to regulate climate change. Otherwise,
the regulatory mechanisms currently in place in the lower 48 U.S.
States have been deemed by the Service to be adequate.
Our Response: Please refer to our December 14, 2010, 12-month
petition finding (75 FR 78030) and our February 4, 2013, proposed rule
to list the North American wolverine (78 FR 7864) for a detailed
evaluation of the discreteness criterion for the contiguous U.S.
population of the wolverine under our DPS policy. In accordance with
that policy, we concluded that this population is discrete based on
differences in control of exploitation and conservation status of the
wolverine across the border between Canada and the United States.
(49) Comment: Many States and public commenters stated that instead
of future predictions of threats, Service should rely on current
population status.
Our Response: Listing decisions under the Act require that we
synthesize current status with threat projections in the future to
determine if the species is presently in danger of extinction
(endangered) or is likely to become endangered in the foreseeable
future (threatened). Following these statutory definitions, it follows
that although an evaluation of current population status may be
sufficiently informative as to whether a species meets the definition
of endangered under the Act, an evaluation of whether a species may be
threatened necessarily invokes additional mechanisms that allow us to
project future scenarios for the species based on scientific data, to
reasonably forecast the conservation status of the species within the
foreseeable future.
(50) Comment: Several commenters said that the threat of poisoning
from 1080 or M-44s should be thoroughly explored in the rule and a
prohibition on incidental take from poisoning should be instituted.
Our Response: Wolverines in the contiguous United States were
likely severely affected by predator poisoning campaigns of the early
20th century. Those types of widespread, indiscriminant, government-
instituted campaigns intending to eliminate predators from the
landscape no longer occur within the range of wolverines. Remaining
predator control efforts are targeted and geographically constrained so
as to target control where predators are particularly problematic for
stock growers and to minimize potential poisoning of non-target
species. There is no evidence that wolverine populations are currently
being affected by poisoning from 1080 or M-44s. Therefore, the best
available information does not indicate that poisoning is a threat to
the DPS.
(51) Comment: Several commenters suggested that current wolverine
population densities and population levels are far below historical
densities and populations. Some also said that the Service should not
speculate as to historical population numbers or densities.
Our Response: There is no reliable estimate for wolverine densities
historically or presently. Current wolverine densities are naturally
low in areas with wolverine populations, and near zero in areas that
have not been recolonized by populations such as the southern Rocky
Mountains and Sierra Nevada Range. Wolverine densities are always
naturally low relative to most other species due to their need for
large territories and their tendency to defend those territories from
other wolverines. Listing under the Act is predicated not on population
densities and size, but rather on whether the species (here DPS) meets
the definition of endangered or threatened because of any of the
following factors: (A) The present or threatened destruction,
modification, or curtailment of its habitat or range; (B)
overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence.
(52) Comment: Several commenters said that mortality from collision
with vehicles on roads is a threat.
Our Response: Wolverine mortality from collisions with vehicles has
occurred in the contiguous United States, but at low levels. Wolverines
use habitats that are not particulary conducive to roads or
transportation corridors. Consequently, wolverines usually do not come
into contact with high-traffic volume roads except in those areas where
highways cross over mountain ranges, usually major passes. There have
been recorded instances of wolverines being killed on roads in valleys
between mountain ranges. These are likely the result of dispersal
attempts by wolverines and appear to be rare occurrences. There is no
evidence that this low level of effect is significant to the status of
the DPS.
(53) Comment: One commenter stated that the Service should analyze
the effects of trapping on wolverine habitat and that trapping itself
modifies or destroys habitat.
Our Response: We cannot conclude that trapping modifies or destroys
habitat. Trapping is a mortality factor but generally does not affect
the ability
[[Page 47531]]
of habitat to provide the life-history requirements of wolverines, such
as food and shelter. The habitat and its ability to support wolverines
remains, but the animal is removed if it is trapped. The important
point is not under what category a threat factor is considered, but
that the effects of the threat factor are considered. The best
available information does not indicate that impacts from trapping
modify or destroy wolverine habitat.
(54) Comment: Several commenters said that we erred in the proposed
listing rule by concluding that wilderness designation provides
protection to wolverines from trapping. They said that trapping is
allowed in wilderness areas, so they do not provide protection.
Our Response: Wilderness designations provide refuge from trapping
by making access to wolverine habitat by trappers more difficult.
Wolverine habitats tend to have very deep snow and cold temperatures
during the trapping season. Most trappers access wolverines by
motorized (snowmobile) transport. Motorized transport is prohibited in
wilderness areas. This reduces, but may not eliminate, trapping in
these areas, providing significant protection.
(55) Comment: One commenter wanted more explanation of why we
concluded in the proposed rule that trapping was not a threat over most
of the DPS.
Our Response: Targeted trapping of wolverines only occurs in
Montana, and occurs at a low level that is compatible with the current
population level. Montana is only a part of the DPS. Therefore,
trapping is not a threat to the entire DPS.
(56) Comment: One commenter disagreed with our statement in the
proposed rule that Montana has stopped trapping in isolated mountain
ranges.
Our Response: The statement in the proposed rule is accurate as
written. Montana has removed wolverine trapping from isolated mountain
ranges in western Montana. The ranges cited in the comments are not
isolated, but are located adjacent to other wolverine habitats.
(57) Comment: One commenter said that in contrast to the 2010 12-
month petition finding, the proposed rule discusses the possible
impacts of human activities very little. The proposed rule also
suggests that research indicates that there is no effect of human
activities, rather than that there is very little research on this
factor.
Our Response: In the proposed listing rule (78 FR 7864; February 4,
2013), we reviewed the information, and consolidated the discussion of
human activities because the lengthy discussion in the 12-month
petition finding (75 FR 78030; December 14, 2010) did not conclude that
there were significant threats from those activities. The proposed rule
concluded that the best available scientific information does not
indicate that a threat to the DPS currently exists from the impacts of
human activities.
(58) Comment: Several commenters suggested that changes to snow
structure caused by freeze/thaws that create hard surface on snow could
increase competition or predation on wolverines by other carnivores.
Our Response: The commenters did not provide any citations with
their comments. We have no information indicating whether such changes
in snow structure are causing impacts to the wolverine.
(59) Comment: One commenter thought that the statement from the
proposed rule that the current population levels in the contiguous
United States may not be lower than those in the past is also
incongruous with population densities in western Canada, where the
population is vastly higher (15,000 to 19,000 individuals) than in the
contiguous United States (USFWS 2013, p. 7869), despite being a
slightly larger yet comparably-sized region.
Our Response: The reported numbers from Canada and Alaska are not
population densities; they are population estimates. Densities are
population per unit of area. The population densities for currently
occupied areas in the DPS are not measurably different from those in
adjacent Canada. Despite the two regions being roughly comparable in
size, the DPS has much less wolverine habitat than Canada and Alaska,
and the habitat that does exist occurs in semi-isolated patches at high
elevations, whereas habitat in Canada and Alaska is much more extensive
and well connected. This explains the difference in wolverine
population numbers between the two areas historically.
(60) Comment: Several commenters said that other risk factors not
considered threats should be considered cumulatively with climate
change.
Our Response: We agree that threat factors must be considered
cumulatively to determine if factors considered together may be a
threat to the species. In the case of the wolverine DPS, in the
proposed rule we concluded that trapping and the effects of small
population size were threats to this growing population only
cumulatively when considered with the projected effects of climate
change on wolverine habitat. However, as described in this document,
upon further consideration of the best available information, we have
re-evaluated our determination on the effects of climate change on
wolverine population persistence in light of new information presented
below under Factor A. We now conclude that there is not sufficient
information on the response of the wolverine DPS to the projected
changes in climate and resulting impacts to habitat, and we do not find
the effects of climate change to likely pose a risk of extinction to
the DPS at this time. We find that absent a threat resulting from
climate change, no other stressor rises to the level of a likely risk
of extinction to the DPS, either individually or cumulatively, that
results in the wolverine DPS meeting the definition of an endangered or
threatened species under the Act.
(61) Comment: One commenter said that wolverine attraction to road
kill is a risk that should be considered.
Our Response: Wolverines have been killed by automobiles on
highways. It is uncertain whether road kill may have been a factor in
some of these mortalities. We have no evidence that highway mortality
is significant to the wolverine population or whether or not attraction
to road kill is a significant contributor to mortality events. This
hypothesis remains speculative until additional scientific evidence is
obtained.
(62) Comment: One commenter opined that heavy recreational use does
not occur in the central Idaho area where the recreation study
(Heinemeyer et al. 2012) is occurring.
Our Response: The term ``heavy'' when used to describe recreational
use is a subjective term. We consider some of the recreational use in
the study area in central Idaho to be locally heavy. The scientists
conducting the study consider the range of recreational use in central
Idaho to be sufficient to detect effects on wolverines from recreation,
if any.
(63) Comment: Many commenters took issue with our conclusions
regarding winter recreation. Some thought that winter recreation is a
threat. Others thought that the recreation study in Idaho could be
interpreted to mean that there are significant effects to wolverines.
Still others thought that the Service should only rely on peer-reviewed
literature when assessing the effects of recreation on the DPS of
wolverines.
Our Response: The best available information does not indicate that
wolverines are significantly affected by winter recreation.
Furthermore, the
[[Page 47532]]
question in the listing process is not whether there is any effect, but
whether that effect rises to such a level of a threat to the DPS such
that the DPS meets the definition of endangered or threatened now or in
the foreseeable future. We find no evidence that winter recreation
occurs on such a scale and has effects that cause the DPS to meet the
definition of a threatened or endangered species. We continue to
conclude that winter recreation, though it likely affects wolverines to
some extent, is not a threat to the DPS.
(64) Comment: Several commenters suggested that changes in
technology make access to wolverine habitat easier for snowmobilers.
Others pointed out that Inman et al. (2013) says snowmobile use may
affect wolverines.
Our Response: We agree that changes in technology increase access
to wolverine habitat by snowmobilers and that winter recreation may
affect wolverines. Significant effects to wolverines from winter
recreation remain to be demonstrated scientifically. We do not agree
that the available scientific information supports the conclusion that
winter recreation is a threat to the DPS, for reasons discussed below
under Factor A.
(65) Comment: One commenter wondered if there is there any
information on wolf predation on wolverines and whether it might be
significant to the listing decision.
Our Response: Wolves have been known to kill wolverines on
occasion, but we are unaware of any information suggesting that wolf
predation is a significant source of mortality for the DPS.
(66) Comment: Several commenters thought that immigration from
Canada would bolster genetic diversity of wolverines in the DPS given
that wolverines recolonized the DPS from Canada.
Our Response: It is possible that future immigration from Canada
will provide for an increase in the genetic diversity of wolverines in
the contiguous United States; however, data presented in Schwartz et
al. (2009) suggest that wolverines are not presently moving between
populations in the DPS and Canada with enough frequency to overcome the
effects of genetic drift.
(67) Comment: Several commenters and States thought that wolverines
may be able to adapt to earlier snowmelt by denning earlier.
Our Response: It is possible that wolverines may be more adaptable
than the currently available scientific information would suggest.
Earlier denning has not been reported for wolverines.
(68) Comment: The listing proposal fails to conduct an independent
assessment of each of the four possible listing options: species, DPS,
significant portion of range of the species, and significant portion of
range of the DPS.
Our Response: In writing the proposed listing rule, we considered
all of the possible listing options, including significant portion of
the range (please refer to Significant Portion of the Range analysis,
below).
(69) Comment: Several commenters suggested that small effective
population size for wolverines in the northern Rocky Mountains is a
significant threat regardless of climate change.
Our Response: In a static population, small effective population
size may be a conservation concern because it can lead to loss of
genetic diversity. In the case of the wolverine DPS, we expect that
continued population growth is likely to ameliorate the effects of
small effective population size by increasing the wolverine population
and providing for better connectivity between subpopulations.
Therefore, small effective population size is not a threat, but rather
a risk factor that may resolve itself as population growth continues.
(70) Comment: Several States commented that there is no provision
in the Act to list a DPS of a subspecies; therefore the DPS is invalid.
Our Response: We continue to support recognition of the wolverine
DPS. The Act provides for recognition of DPSs for vertebrate species.
The word ``species'' in that context refers to species or subspecies.
Furthermore, our 1996 Policy Regarding the Recognition of Distinct
Vertebrate Population Segments Under the Endangered Species Act states:
``The Services maintain that the authority to address DPS's extends to
species in which subspecies are recognized, since anything included in
the taxon of lower rank is also included in the higher ranking taxon''
(61 FR 4722, p. 4724; February 7, 1996). Therefore, it is appropriate
to recognize the wolverine DPS as a listable entity.
Summary of Factors Affecting the Species
Section 4 of the Act (16 U.S.C. 1533), and its implementing
regulations at 50 CFR part 424, set forth the procedures for adding
species to the Federal Lists of Endangered and Threatened Wildlife and
Plants. Under section 4(a)(1) of the Act, we may list a species based
on (A) The present or threatened destruction, modification, or
curtailment of its habitat or range; (B) overutilization for
commercial, recreational, scientific, or educational purposes; (C)
disease or predation; (D) the inadequacy of existing regulatory
mechanisms; or (E) other natural or manmade factors affecting its
continued existence. Listing actions may be warranted based on any of
the above threat factors, singly or in combination. Each of these
factors is discussed below.
Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of Its Habitat or Range
Under Factor A, we will discuss a variety of impacts to wolverine
habitat including: (1) Effects of climate change, (2) human use and
disturbance, (3) dispersed recreational activities, (4) infrastructure
development, (5) transportation corridors, and (6) land management.
Many of these impact categories overlap or act in concert with each
other to affect wolverine habitat. Climate change effects are discussed
under Factor A because although increased temperatures due to climate
change may affect wolverines directly by creating physiological stress,
the primary potential impact of climate change on wolverines is thought
to be through changes to the availability and distribution of wolverine
habitat.
Reduction in Habitat Due to Climate Change
Our analyses under the Act include consideration of the likely
effects of ongoing and projected changes in climate. The terms
``climate'' and ``climate change'' are defined by the Intergovernmental
Panel on Climate Change (IPCC). ``Climate'' refers to the mean and
variability of different types of weather conditions over time, with 30
years being a typical period for such measurements, although shorter or
longer periods also may be used (IPCC 2013, p. 1450). The term
``climate change'' thus refers to a change in the mean or variability
of one or more measures of climate (e.g., temperature or precipitation)
that persists for an extended period, typically decades or longer,
whether the change is due to natural variability, human activity, or
both (IPCC 2013, p. 1450). Various types of changes in climate can have
direct or indirect effects on species. These effects may be positive,
neutral, or negative and they may change over time, depending on the
species and other relevant considerations, such as the effects of
interactions of climate with other variables (e.g., habitat
fragmentation) (IPCC 2007, pp. 8-14, 18-19).
We recognize that there are scientific uncertainties on many
aspects of
[[Page 47533]]
climate change, including the role of natural variability in climate.
In our listing proposal (78 FR 7874-7877), we relied both on synthesis
documents (e.g., IPCC 2007; Karl et al. 2009) that present the
consensus view of a very large number of experts on climate change from
around the world, and on analyses that relate the effects of climate
change directly to wolverines (Brock and Inman 2007, pers. comm.;
Gonzalez et al. 2008, entire; Brodie and Post 2009, entire; Peacock
2011, entire; McKelvey et al. 2011, entire; Johnston et al. 2012,
entire). We argued that due to lack of downscaling (Peacock 2011),
failure to consider both temperature and precipitation (Brock and Inman
2007, pers. comm.; Gonzalez et al. 2008), limited analysis area
(Johnson et al. 2012), and inappropriate inferences from harvest data
(Brodie and Post 2010), many analyses do not represent the best
available science. In our proposed listing rule, we identified McKelvey
et al. (2011) as the best scientific information available regarding
impacts of climate change to wolverine habitat because the authors
incorporated both temperature and precipitation, and downscaled
analyses to reflect the regional climate patterns and topography found
within the range of wolverines in the contiguous United States.
While we still agree that McKelvey et al. (2011) is the most
sophisticated analysis of impacts of climate change at a scale specific
to the range of the wolverine, science panel members (Service 2014, p.
29), public comments, and recent scientific information (Potter et al.
2013, entire; Franklin et al. 2012, entire) emphasize limitations
inherent in downscaled climate models and the importance of
understanding the effect of climate-data spatial resolution on
wolverine viability in complex terrain. Downscaling techniques improve
understanding of climate at smaller, regional scales compared to Global
Climate Models, but their spatial resolution may still be inadequate to
describe the variability of microclimates in which organisms live
(Potter et al. 2013, p. 2935). Franklin et al. (2012, pp. 478-482) show
that there can be large differences between suitable habitats predicted
from coarse versus fine-scale climate models, and concluded that, on
average, a scale approximately twice as fine as that used in McKelvey
et al. (2011, entire) (280 m vs. 500 m) is adequate, and that in rugged
terrain even finer models (e.g., 10-30 m) may be needed to represent
significant microclimates. Potter et al. (2014, p. 2934) propose that
the ideal spatial resolution is related to organismal body size and
lies between 1 and 10 times the length or height of the organism.
McKelvey et al. (2011, p. 2895) reached similar conclusions about their
own modeling efforts: ``although wolverine distribution is closely tied
to persistent spring snow cover (Copeland et al. 2010), we do not know
how fine scale changes in snow patterns within wolverine home range may
affect population persistence.'' We concur; an improved understanding
of how microclimatic variation alters the habitat associations of
wolverines at fine spatial scales will be useful in understanding
climate impacts on wolverine habitat.
Additionally, great difficulty still exists in predicting changes
in precipitation with climate models, especially compared to the more
confident predictions for temperature (Torbit 2014, pers. comm.). Newer
modeling techniques suggest that higher elevations could maintain more
snow than previously thought and possibly even receive more snow than
historical records show due to climate change (Torbit 2014, pers.
comm.; Ray et al. 2008). While these contemporary techniques have not
been applied to the northern portions of the proposed wolverine DPS (78
FR 7873), and much of the high elevation wolverine range is currently
unoccupied, they demonstrate that the science associated with climate
models is continuing to change, highlighting the uncertainty of our
conclusions in the proposed rule (78 FR 7877). This new information
highlighting the importance of scale and use of modern, quantitative
techniques to evaluate uncertainty in climate assessments have prompted
us to re-evaluate our original conclusions in the proposed rule (78 FR
7874-7876) that wolverine habitat will decline at the predicted rates
suggested in McKelvey et al. (2011). Modern assessment techniques that
include slope, aspect, and other topographic information are now
available and can be used to predict precipitation, including snowfall
at finer scales that could be more aligned with existing or potential
wolverine habitat (Torbit 2014, pers. comm.; Ray et al. 2008, pp. 17-
23; Torbit 2014, pers comm). Based upon our re-evaluaton of the best
scientific data available, we no longer find that the existing
scientific information supports our conclusions in the proposed rule
(78 FR 7874-7876) that climate change will result in a 31 percent (mid-
century) to 63 percent (end of century) reduction in wolverine habitat
in the foreseeable future.
Climate Effects to Wolverines
We based our proposal (78 FR 7874-7877) on the best available data
at the time, which we intitially interpreted as demonstrating that
wolverines require deep snow persisting through the denning period to
successfully live and reproduce, and that reduction of this habitat
feature would proportionally reduce wolverine habitat, or to an even
greater extent if habitat reduction involved increasing fragmentation.
We analyzed the effects of climate change on wolverines through three
primary mechanisms: (1) Reduced snowpack and earlier spring runoff,
which we argued would reduce suitable habitat for wolverine denning;
(2) increase in summer temperatures beyond the physiological tolerance
of wolverines; and (3) ecosystem changes due to increased temperatures,
which we reasoned would move lower elevation ecosystems to higher
elevations, thereby eliminating high-elevation ecosystems on which
wolverines depend and increasing competitive interactions with species
that currently inhabit lower elevations. These mechanisms would tend to
push the narrow elevational band that wolverines use into higher
elevation, and due to the conical structure of mountains, this upward
shift would result in reduced overall suitable habitat for wolverines.
Deep Snow and Denning
The literature generally does not reflect any studies that tested
whether wolverines have an obligate relationship with deep and/or
contiguous snow cover; therefore, we convened an expert science panel
to provide further guidance specifically on this issue (Service 2014,
entire). Expertise included climatologists and remote sensing experts,
biologists, and ecologists. Panelists strongly supported an obligate
relationship between wolverines and deep snow at the scale of the den
site, expressed uncertainty in the relationship between wolverines and
deep snow at the scale of the home range and DPS' range, and also
expressed uncertainty in the relationship between wolverines and
contiguous snow at the home range and DPS range scales (Service 2014,
pp. 8-13). Therefore, based on the literature (Pulliainen 1968;
Copeland 1996; Magoun and Copeland 1996; Magoun and Copeland 1998;
Banci 1994; Inman et al. 2007; Copeland et al. 2010), the opinion of
expert panelists, and the peer reviews, it is reasonable to believe
that wolverines select for den sites likely to have deep snow that will
persist until some point into the spring.
[[Page 47534]]
The primary hypothesis put forward in the proposed listing rule (78
FR 7875) is that a loss of areas with persistent spring snow cover will
result in a loss of potential wolverine den sites, or failure of den
sites, negatively impacting future abundance and trend. Den sites are
correlated with snow (Copeland et al. 2010, entire), and experts in the
science panel expressed an opinion that wolverines require deep snow
for den sites. However, the predictions from McKelvey et al. (2011)
about future habitat loss rely on the Copeland model (Copeland et al.
2010, entire) to describe what habitat is and then to predict how much
of it will be lost. The habitat described in the Copeland model
includes areas that retained snow until May 15, in as few as 1 of 7
years. In other words, if an area retained snow in only 1 of 7 years,
it was still included in the model describing habitat, and 97.9 percent
of the sample of den sites fell within this area. That means that some
proportion of those den sites fell within an area that did not retain
snow each year. This brings into question the reliability of the
conclusion that snow persisting until May 15 is a necessary condition
for wolverine reproduction.
We are aware of no evidence that den sites are currently scarce or
lacking, or that they currently limit wolverine reproduction. In other
words, even if some den sites were to be lost as a result of climate
change, due to the expansive size of female wolverine home ranges, it
is likely that many potential additional den sites would remain
available. Further, we have no information that we could use to predict
at what level of reduced spring snow coverage den sites would become
limiting. Inman et al. (2013) estimated available habitat capacity in
the U.S. to be approximately 644 wolverines (95 percent CI = 506-1881),
and that current population size is currently approximately half of
capacity. This estimated current abundance level (322) is similar to
our rough estimate of population abundance of 250-300 wolverines in our
proposed listing rule. The current estimated abundance level,
significantly below estimated carrying capacity for a population that
is still increasing, suggests that den sites are likely not currently
limiting wolverine reproduction and population abundance.
We do not appear to know at this point with any reliability what
the causal relationship is between the feature of deep persistent
spring snow and wolverine dens (Service 2014, pp. 10, 28-29); that is,
we do not understand why wolverines appear to require deep persistent
spring snow for denning. Several hypotheses exist to explain the
correlation between den sites and snow, such as den structure, food
refrigeration, security from predators, or a thermal buffer for kits in
the den, but these hypotheses have not been tested. All of these
hypotheses seem possible and worth testing, but without such biological
information demonstrating the causal mechanism, it is difficult to
determine beyond speculation if, and how soon, the effects of climate
change (e.g., earlier snowmelt) may influence or limit availability of
den sites, habitat, and ultimately wolverine abundance, trend, and
viability into the future.
Only two studies have investigated hypotheses regarding potential
limiting factors for wolverines. Persson (2005) tested the hypothesis
that wolverine reproduction was affected by winter food availability.
He found that provision of additional food resources to wolverines,
when compared to a control group not receiving supplemental food,
resulted in higher reproduction. He suggests that female wolverine
reproduction is determined by their condition in winter, which is
determined by past year's reproductive costs and food availability. In
his comments on the proposed listing rule, Copeland (November 26, 2013,
p. 2) also touched on food availability as the limiting factor as he
stated his belief that wolverine densities are highly variable and tied
to food availability. He points to current differences in population
densities between Glacier National Park and central Idaho that he
believes are most likely related to food availability. He hypothesized
that Glacier Park provides a year-round higher availability of carrion
and therefore higher densities of wolverines.
In summary, the pertinent question that remains is if and when a
decrease in deep, persistent spring snow will limit the availability of
den sites, therefore causing a population decline in the future.
Available information does not yet allow us to predict if and when that
may occur.
Year-Round Relationship Between Wolverine Habitat and Persistent Snow
Cover
Copeland et al. (2010) estimated persistent spring snow cover
(April 24 to May 15 in at least 1 of 7 years during the period from
2000 to 2006, Copeland et al. (2010, p. 235)) using MODIS satellite
data, and the resulting mapped area represents their bioclimatic model
describing wolverine habitat (Copeland et al. 2010, Figure 1). They
indicated that of the total 562 dens from North America, Finland,
Norway, and Sweden, 97.9 percent of den sites occurred in pixels that
were snow covered through May 15 in at least 1 of the 7 years (that is,
they were within the modeled habitat). Their results indicated that not
all, but 95 percent of summer and 86 percent of winter telemetry
locations of wolverine, were within the modeled habitat area they
described as having persistent deep snow cover.
However, the location dataset relies heavily on data collected in
Scandinavia and does not consider several available datasets, such as
trapping locations, location records from States and provinces, and
telemetry data from the eastern Canadian provinces. In their comments,
the State of Idaho indicated that only 68.6 percent of Idaho's verified
wolverine observations (312 of 415) were within Copeland et al.'s
(2010) habitat model (Idaho Fish and Game Comments, November 25, 2013,
p. 2). Recent publications have suggested that factors beyond those
included by Copeland et al. (2010) such as land cover (e.g., vegetative
type), topography, human footprint, and snow depth should be
incorporated into predictive models to accurately describe wolverine
habitat because these factors appear to also influence primary
wolverine habitat use (Inman et al. 2013, p. 278; Fisher et al. 2013,
p. 712). These publications appear to support the idea that wolverines
generally use areas of higher elevation; steeper terrain; more snow;
fewer roads; less human activity; and, generally, snow cover persisting
into the spring. Note, however, that Inman et al. (2013, p. 278) used
snow cover on April 1, not snow cover until May 15, as a variable in
their best-fitting model. Lastly, Copeland himself (November 26, 2013,
p. 2) stated his belief that there are other factors beyond snow that
influence wolverine distribution. Taken together, the available body of
literature, our peer review, the science panel (Service 2014, entire),
and public comment appear to indicate that: (1) Wolverines use areas
with deep snow; (2) wolverines are occasionally observed outside of the
area that has snow until May 15; (3) areas were included in the
Copeland et al. (2010) predictive habitat model that may have had May
15 snow in as little as 1 of 7 years studied; and (4) factors other
than snow cover on May 15 may also influence wolverine habitat use.
McKelvey et al. (2011, Figure 4) suggested that wolverine habitat
in the contiguous United States, which currently supports approximately
250 to 300 wolverines, is shrinking and will likely continue to shrink
and become increasingly fragmented with increased
[[Page 47535]]
climate warming. They projected a 31 percent in habitat loss throughout
the range of the DPS by the time interval centered on 2045 (2030-2059).
That loss expands to 63 percent of wolverine habitat by the time
interval centered on 2085 (2070 to 2099). In our proposed listing rule,
we reasoned that due to the spatial needs of wolverines and the limited
availability of suitable wolverine habitat in the contiguous United
States, this projected habitat loss would be likely to result in a loss
of wolverine numbers that is greater than the overall loss of habitat
area. However, upon reconsideration of the best available information,
given our uncertainty in the relationship between wolverines and snow,
we conclude it is not clear that these predictions of snow loss
represent an equivalent loss of habitat. That is, while it may be
likely that habitat will decrease over time due to earlier snow melt,
if wolverines also use areas outside of the area covered with snow
until May 15, this reduction in snow cover may not equate linearly to
an equivalent loss of wolverine habitat; thus, McKelvey et al. (2011)
may overestimate the loss of wolverine habitat (Franklin et al. 2013,
p. 481).
Furthermore, based on our own calculations, given average home
range sizes of male and female wolverines, the predicted habitat
remaining after 2085 (McKelvey et al. 2010) could support 344 (95
percent CI: 250-421) wolverines (versus the current estimate of 250-
300) in the contiguous United States, with the bulk (283; 95 percent
CI: 110-347) of individuals estimated in the Northern Rocky Mountains
in 2070-2099. These estimates do not include possible additional
occupancy of potentially important wolverine habitat in the Sierra
Nevada Mountains and portions of Oregon, which were beyond the
geographic scope of the McKelvey et al.'s (2011) analysis. In other
words, even under future conditions of projected habitat loss, we
estimate there would be sufficient habitat available in the United
States to potentially continue supporting wolverine populations at
roughly the same level of abundance as at present. Thus, even if future
populations were potentially limited by available habitat for future
growth, the data do not suggest that the population of wolverines in
the contiguous United States would necessarily be forced into decline
by loss of habitat. In addition, as discussed above, if the obligate
relationship with deep snow is only at the den site and not across the
overall range of a wolverine and the DPS in general, specific snow
variation due to elevation and topography also calls into question the
conclusion that overall snow loss across the range of the DPS will
equate to a specific loss of wolverine habitat.
Our proposed listing rule also discussed the consequences of
habitat patches becoming progressively isolated from each other due to
climate change (78 FR 7876). We concluded that reduced connectivity to
other subpopulations could increase the likelihood of subpopulations
lost due to demographic stochasticity, impairing the functionality of
the wolverine metapopulation in the contiguous United States. McKelvey
et al. (2011) concluded that continued warming trends may create small
and isolated populations, among which the energetic costs of traveling
will be high. However, they also stated that while contiguous areas of
spring snow cover are predicted to become smaller and more isolated
over time, large (>2000 km\2\) contiguous areas of wolverine habitat
are predicted to persist within the study area throughout the 21st
century for all model projections (McKelvey et al. 2011, pp. 2992,
2994). By the late 21st century, their dispersal modeling predicts that
habitat isolation at levels associated with genetic isolation of
populations becomes widespread.
Currently available information indicates that wolverines are known
to travel long distances through anthropogenically altered terrain, and
habitats that are otherwise unsuitable for long-term survival (Moriarty
et al., entire; Inman et al. 2009, pp. 22-28); in fact, this propensity
was cited as complicating our analysis of present and past range (78 FR
7869). Wolverines are able to successfully disperse between habitats,
despite the level of development that is currently taking place in the
current range of the DPS (Copeland 1996, p. 80; Copeland and Yates
2006, pp. 17-36; Inman et al. 2007a, pp. 9-10; Pakila et al. 2007, pp.
105-109; Schwartz et al. 2009, Figures 4, 5). In recent years,
individual wolverines have been documented in Colorado (2010), the
Sierra Nevada range in California (2008), and the Uinta Range of Utah
and Wyoming (2014), indicating some dispersal to known unoccupied range
is occurring, and quite likely necessitated travel through lower
elevation areas that do not retain deep snow. Although most studies
document greater dispersal distances for males than females (Hornocker
and Hash 1981, p. 1298; Banci 1994, pp. 117-118; Moriarty et al. 2009,
entire; Inman et al. 2009, pp. 22-28; Brian 2010, p. 3; Copeland and
Yates 2006, Figure 9), Vangen et al. (2001, p. 1644) found that both
males and females are capable of long-distance dispersal. One hundred
percent of males and 69 percent of females dispersed, with average
dispersal distances for males of 51 30km (range = 11-101
km) and 60 48 km (range = 15-178 km) for females, although
differences between males and females were not significant. Vangen et
al. (2001, p. 1647) reflect on other dispersal distances reported in
the literature from Idaho (two males dispersed 16 and 199 km; Copeland
1996) and Alaska (one male dispersed 378 km; Gardner 1985) and
concluded that both sexes have the capacity to establish themselves far
away from their natal areas, thereby ensuring recolonization and gene
flow between subpopulations. Inman et al. (2013, p. 284), however,
suggest that female long-distance dispersal is likely to be very
infrequent.
Given the available body of literature, the proposed listing rule
(78 FR 7864; February 4, 2013), science panel (Service 2014, entire),
and peer review, it is reasonable to predict that if observed warming
trends (Hamlet and Lettenmaier 1999, p. 1609; Brown 2000, p. 2347; Mote
2003, p. 3-1; Christensen et al. 2004, p. 347; Knowles et al. 2006, pp.
4548-4549) continue within the larger range of wolverine, and areas
with deep snow become smaller and more isolated, connectivity and
genetic exchange among wolverine populations will decrease over time.
At the same time, however, as discussed above, relatively large areas
of wolverine habitat are predicted to persist throughout the 21st
century for all model projections, and wolverines are capable of
traversing great lengths, thus ameliorating the potential negative
consequences of increasing distances between areas of suitable habitat.
Therefore, as discussed above, with such uncertainty in wolverine
response to changes predicted association with climate modeling, we do
not know if and to what extent genetic exchange will be limited and in
what timeframe. Furthermore, the best available information does not
indicate that climate change effects have hindered population growth
and expansion, or caused any contraction of habitat at this time (Inman
et al. 2013, p. 277).
We acknowledged in our proposed listing rule (78 FR 7868; February
4, 2013), that with no systematic census across the range of the DPS in
the United States, the current population level of wolverines is not
known with certainty. As we stated in the proposal, our best estimate
of current population abundance was based on knowledge of occupied
habitat and average densities: approximately 250 to 300 wolverines in
[[Page 47536]]
the lower 48 States. Since the proposed listing rule was published,
Inman et al. (2013) published an estimated available habitat capacity
to be approximately 644 wolverines (95 percent CI = 506-1881), and
estimated that the current population size in the contiguous United
States is currently approximately half of capacity (in other words,
roughly 322 individuals), and these are believed to be expanding in
number and range (Aubry et al. 2007, p. 2151). Population growth and
expansion has been documented in the North Cascades and Northern Rocky
Mountains (78 FR 7881-7872), and as has been noted above, individuals
have successfully dispersed to Colorado, California and Utah. This
estimated current abundance level (322) is similar to our rough
estimate of population abundance of 250-300 wolverines in our proposed
listing rule. Accordingly, our conclusion in the proposed rule (78 FR
78049) that climate change has likely already reduced the overall areal
extent and distribution of wolverine habitat seems largely speculative.
While one could conjecture that dispersers to the southern portion of
the DPS are occurring due to habitat loss in the northern part of the
DPS, one could just as easily conclude that these dispersers are the
result of an increasing population with dispersers looking to colonize
largely unoccupied habitat. This consideration, coupled with the
results of the Inman et al. (2013) publication indicating that
available habitat could support a population in the United States twice
as large as that at present, suggests that there is no evidence of
habitat contraction at this time due to climate change.
Finally, our proposal suggested that the projected increase in
summer temperatures and elimination of high-elevation ecosystems on
which wolverines depend may negatively impact wolverines. We reiterate
our earlier discussion of the limitations and uncertainty inherent in
downscaled climate models. Available information suggests that climate
changes may indeed affect wolverine habitat; however, the specific
response or sensitivity of the wolverines to these current and
forecasted changes is sufficiently uncertain at this time, such that we
cannot reasonably project the future conservation status of the DPS
based on any such changes that may occur.
Summary of Impacts of Climate Changes
There is significant evidence that the climate within the larger
range of the wolverine is warming, affecting snow patterns and
associated wolverine habitat. The biological response of wolverine
populations to such changes, however, cannot reasonably be deduced with
an acceptable degree of certainty. At this time, we do not know how the
effects of climate change will impact wolverine populations for the
following reasons:
(1) Wolverines are believed to be expanding both within the area
currently inhabited by wolverines as well as into suitable habitat not
currently occupied and/or occupied with a few individuals. Recent
evidence suggests that there is suitable habitat available within the
contiguous United States to support a wolverine population twice as
large as that at present. Even under conditions of future reduced
snowpack as a consequence of climate change, sufficient habitat will
likely remain to maintain the wolverine population at the current level
of abundance.
(2) There is strong support for the existence of an obligate
relationship between wolverines and deep spring snow at the den site;
however, available information suggests that den sites are not
currently limiting wolverines, and we do not have sufficient
information to predict if and when any limitation will occur in the
future. Additionally, support for the obligate relationship between
wolverine and deep snow at an individual wolverine's home range or the
DPS' range in general is lacking. That is, we do not have sufficient
information to suggest that deep snow is required by wolverines
throughout their home ranges, beyond the level of the individual den
site.
(3) We do not have sufficient information to understand the
specific response of wolverines to future effects of changes in
climate. Although we do not question that climate change is likely to
alter the habitats utilized by wolverines to some degree, we have no
data to inform us as to the likely biological response of wolverine
populations to those habitat changes, and, most germane for the
purposes of the Act, no data to reliably suggest that the anticipated
changes are such that the viability of wolverine populations in the
contiguous United States will be at risk.
Therefore, based on our analysis of the best available scientific
information, we do not find the effects of climate change to likely
place the wolverine DPS in danger of extinction in the foreseeable
future and therefore meeting the definition of a threatened species
under the Act.
Habitat Impacts Due to Human Use and Disturbance
Because wolverine habitat is generally inhospitable to human use
and occupation and most wolverine habitat is also federally managed in
ways that must consider environmental impacts, wolverines are somewhat
insulated from impacts of human disturbances from industry,
agriculture, infrastructure development, or recreation. Human
disturbance in wolverine habitat in the contiguous United States has
likely resulted in the loss of some minor amount of wolverine habitat,
although this loss has not yet been quantified. Sources of human
disturbance to wolverines has been speculated to include winter and
summer recreation, housing and industrial development, road corridors,
and extractive industry (such as logging or mining). In the contiguous
United States, these human activities and developments sometimes occur
within or immediately adjacent to wolverine home ranges, such as in
alpine or boreal forest environments at high elevations on mountain
slopes. They can also occur in a broader range of habitats that are
occasionally used by wolverines during dispersal or exploratory
movements--habitats that are not suitable for the establishment of home
ranges and reproduction.
Little is known about the behavioral responses of individual
wolverines to human presence, or about the DPS' ability to tolerate and
adapt to repeated human disturbance. Some hypothesize that disturbance
may reduce the wolverine's ability to complete essential life-history
activities, such as foraging, breeding, maternal care, routine travel,
and dispersal (Packila et al. 2007, pp. 105-110). However, wolverines
have been documented to persist and reproduce in areas with high levels
of human use and disturbance including developed alpine ski areas and
areas with motorized use of snowmobiles (Heinenmeyer 2012, entire).
This suggests that wolverines can survive and reproduce in areas that
experience human use and disturbance. How or whether effects of
disturbance extend from individuals to characteristics of
subpopulations and populations, such as vital rates (e.g.,
reproduction, survival, emigration, and immigration) and gene flow, and
ultimately to wolverine population or metapopulation persistence,
remains unknown at this time.
Wolverine habitat is characterized primarily by spring snowpack,
but also by the absence of human presence and development (Hornocker
and Hash 1981, p. 1299; Banci 1994, p. 114; Landa
[[Page 47537]]
et al. 1998, p. 448; Rowland et al. 2003 p. 101; Copeland 1996, pp.
124-127; Krebs et al. 2007, pp. 2187-2190). This negative association
with human presence is sometimes interpreted as active avoidance of
human disturbance, but it may simply reflect the wolverine's preference
for cold, snowy, and high-elevation habitat that humans avoid. In the
contiguous United States, wolverine habitat is typically associated
with high-elevation (e.g., 2,100 m to 2,600 m (6,888 ft to 8,528 ft))
subalpine forests that comprise the Hudsonian Life Zone (weather
similar to that found in northern Canada), environments not typically
used by people for housing, industry, agriculture, or transportation.
However, a variety of activities associated with extractive industry,
such as logging and mining, as well as recreational activities in both
summer and winter are located in a small amount of occupied wolverine
habitat.
For the purposes of this determination, we analyze human
disturbance in four categories: (1) Dispersed recreational activities
with primary impacts to wolverines through direct disturbance (e.g.,
snowmobiling and heli-skiing); (2) disturbance associated with
permanent infrastructure, such as residential and commercial
developments, mines, and campgrounds; (3) disturbance and mortality
associated with transportation corridors; and (4) disturbance
associated with land management activities, such as forestry or fire/
fuels reduction activities. Overlap between these categories is
extensive, and it is often difficult to distinguish effects of
infrastructure from the dispersed activities associated with that
infrastructure. However, we conclude that these categories account for
most of the human activities that occur in occupied wolverine habitat.
Dispersed Recreational Activities
Dispersed recreational activities occurring in wolverine habitat
include snowmobiling, heli-skiing, hiking, biking, off- and on-road
motorized use, hunting, fishing, and other uses.
One study documented (in two reports) the extent that winter
recreational activity spatially and temporally overlapped modeled
wolverine denning habitat in the contiguous United States (Heinemeyer
and Copeland 1999, pp. 1-17; Heinemeyer et al. 2001, pp. 1-35). This
study took place in the Greater Yellowstone Area (GYA) in an area of
high dispersed recreational use. The overlap of modeled wolverine
denning habitat and dispersed recreational activities was extensive.
Strong temporal overlap existed between snowmobile activity (February-
April) and the wolverine denning period (February-May). During 2000,
six of nine survey units, ranging from 3,500 to 13,600 (ha) (8,645 to
33,592 (ac)) in size, showed evidence of recent snowmobile use. Among
the six survey units with snowmobile activity, the highest use covered
20 percent of the modeled denning habitat, and use ranged from 3 to 7
percent over the other survey units. Snowmobile activity was typically
intensive where detected.
Three of nine survey units in this study showed evidence of skier
activity (Heinemeyer and Copeland 1999, p. 10; Heinemeyer et al. 2001,
p. 16). Among the three units with activity, skier use covered 3 to 19
percent of the survey unit. Skiers also intensively used the sites they
visited. Combined skier and snowmobile use covered as much as 27
percent of potential denning habitat in one unit where no evidence of
wolverine presence was detected. We conclude from this study that in
some areas, high recreational use may coincide substantially with
occupied wolverine habitat. The authors of the study cited above chose
the study area based on its unusually high level of motorized
recreational use. Although we do not have information on the overlap of
wolverine and winter recreation in the remaining part of the contiguous
U.S. range, it is unlikely that any of the large areas of wolverine
habitat such as the southern Rocky Mountains, Northern Rocky Mountains,
GYA, or North Cascades get the high levels of recreational use seen in
the portion of the GYA examined in this study across the entire
landscape. Rather, each of these areas has small (relative to wolverine
home range size) areas of intensive recreational use (ski resorts,
motorized play areas) surrounded by a landscape that is used for more
dispersed recreation such as backcountry skiing or snowmobile trail
use.
Although we can demonstrate that recreational use of wolverine
habitat is heavy in some areas, we do not have any information to
suggest that these activities have negative effects on wolverines. No
assessments of anthropogenic disturbance on wolverine den fidelity,
food provisioning, or offspring survival have been conducted.
Disturbance from foot and snowmobile traffic associated with historical
wolverine control activities (Pulliainen 1968, p. 343), and field
research activities, have been purported to cause maternal females to
abandon natal dens and relocate kits to maternal dens (Myrberget 1968,
p. 115; Magoun and Copeland 1998, p. 1316; Inman et al. 2007c, p. 71).
However, this behavior appears to be rare, even under intense
disturbance associated with capture of family groups at the den site
(Persson et al. 2006, p. 76), and other causes of den abandonment may
have acted in these cases. Preliminary results from an ongoing study on
the potential impacts of winter recreation on wolverines in central
Idaho indicate that wolverines are present and reproducing in this area
in spite of heavy recreational use, including a developed ski area;
dispersed winter and summer recreation; and dispersed snowmobile use
(Heinemeyer et al. 2012, entire). The security of the den and the
surrounding foraging areas (i.e., protection from predation by
carnivores) is an important aspect of den site selection. Abandonment
of natal and maternal dens may be a preemptive strategy that females
use in the absence of predators (i.e., females may abandon dens without
external stimuli), as this may confer an advantage to females if
prolonged use of the same den makes that den more evident to predators.
Evidence for effects to wolverines from den abandonment due to human
disturbance is lacking. The best scientific information available does
not substantiate dispersed recreational activities as a threat to
wolverine.
Most roads in wolverine habitat are low-traffic volume dirt or
gravel roads used for local access. Larger, high-volume roads are dealt
with below in the section ``Transportation Corridors.'' At both a site-
specific and landscape scale, wolverine natal dens were located
particularly distant from public (greater than 7.5 km (4.6 mi)) and
private (greater than 3 km (1.9 mi)) roads (May 2007, pp. 14-31).
Placement of dens away from public roads (and away from associated
human-caused mortality) was also a positive influence on successful
reproduction. It is not known if the detected correlation is due to the
influence of the roads, but we find it unlikely that wolverines avoid
the type of low-use forest roads that generally occur in wolverine
habitat. Other types of high-use roads are rare in wolverine habitat
and are not likely to affect a significant amount of wolverine habitat
(see ``Transportation Corridors'' section, below).
Infrastructure Development
Infrastructure includes all residential, industrial, and
governmental developments, such as buildings, houses, oil and gas
wells, and ski areas. Infrastructure development on private lands in
the Rocky Mountain West has been rapidly increasing in recent years
[[Page 47538]]
and is expected to continue as people move to this area for its natural
amenities (Hansen et al. 2002, p. 151). Infrastructure development may
affect wildlife directly by eliminating habitats, or indirectly, by
displacing animals from suitable habitats near developments.
Wolverine home ranges generally do not occur near human
settlements, and this separation is largely due to differential habitat
selection by wolverines and humans (May et al. 2006, pp. 289-292;
Copeland et al. 2007, p. 2211). In one study, wolverines did not
strongly avoid developed habitat within their home ranges (May et al
2006, p. 289). Wolverines may respond positively to human activity and
developments that are a source of food. They scavenge food at dumps in
and adjacent to urban areas, at trapper cabins, and at mines (LeResche
and Hinman 1973 as cited in Banci 1994 p. 115; Banci 1994, p. 99).
Based on the best available science, we conclude that wolverines do not
avoid human development of the types that occur within suitable
wolverine habitat.
There is no evidence that wolverine dispersal is affected by
infrastructure development. Linkage zones are places where animals can
find food, shelter, and security while moving across the landscape
between suitable habitats. Wolverines prefer to travel in habitat that
is most similar to habitat they use for home-range establishment, i.e.,
alpine habitats that maintain snow cover well into the spring (Schwartz
et al. 2009, p. 3227). Wolverines may move large distances in an
attempt to establish new home ranges, but the probability of making
such movements decreases with increased distance between suitable
habitat patches, and the degree to which the characteristics of the
habitat to be traversed diverge from preferred habitat in terms of
climatic conditions (Copeland et al. 2010, entire; Schwartz et al.
2009, p. 3230).
The level of development in these linkage areas that wolverines can
tolerate is unknown, but it appears that the current landscape does
allow wolverine dispersal (Schwartz et al. 2009, Figures 4, 5; Moriarty
et al. 2009, entire; Inman et al. 2009, pp. 22-28). For example,
wolverine populations in the northern Rocky Mountains appear to be
connected to each other at the present time through dispersal routes
that correspond to habitat suitability (Schwartz et al. 2009, Figures
4, 5).),
Wolverines are capable of long-distance movements through variable
and anthropogenically altered terrain, crossing numerous transportation
corridors (Moriarty et al. 2009, entire; Inman et al. 2009, pp. 22-28).
Wolverines are able to successfully disperse between habitats, despite
the level of development that is currently taking place in the current
range of the DPS (Copeland 1996, p. 80; Copeland and Yates 2006, pp.
17-36; Inman et al. 2007a, pp. 9-10; Pakila et al. 2007, pp. 105-109;
Schwartz et al. 2009, Figures 4, 5). Dispersal between populations is
needed to avoid further reduction in genetic diversity; however, there
is no evidence that human development and associated activities are
preventing wolverine movements between suitable habitat patches.
Rather, wolverine movement rates are limited by suitable habitat and
proximity of suitable habitat patches, not the characteristics of the
intervening unsuitable habitat (Schwartz et al. p. 3230).
Transportation Corridors
Transportation corridors are places where transportation
infrastructure and other forms of related infrastructure are
concentrated together. Examples include interstate highways and high-
volume secondary highways. These types of highway corridors often
include railroads; retail, industrial, and residential development; and
electrical and other types of energy transmission infrastructure.
Transportation corridors may affect wolverines if located in wolverine
habitat or between habitat patches. If located in wolverine habitat,
transportation corridors result in direct loss of habitat. Direct
mortality due to collisions with vehicles is also possible (Packila et
al. 2007, Table 1).
The Trans Canada Highway at Kicking Horse Pass in southern British
Columbia, an important travel corridor over the Continental Divide, has
a negative effect on wolverine movement (Austin 1998, p. 30).
Wolverines partially avoided areas within 100 m (328 ft) of the
highway, and preferred to use distant sites (greater than 1,100 m
(3,608 ft)). Wolverines that approached the highway to cross repeatedly
retreated, and successful crossing occurred in only half of the
attempts (Austin 1998, p. 30). Highway-related mortality was not
documented in the study. Where wolverines did successfully cross, they
used the narrowest portions of the highway right-of-way. A railway with
minimal human activity, adjacent to the highway, had little effect on
wolverine movements. Wolverines did not avoid, and even preferred,
compacted, lightly used ski trails in the area. The extent to which
avoidance of the highway may have affected wolverine vital rates or
life history was not measured.
In the tri-State area of Idaho, Montana, and Wyoming, most
documented crossings of Federal or State highways were done by subadult
wolverines making exploratory or dispersal movements (ranges of
resident adults typically do not contain major roads) (Packila et al.
2007, p. 105). Roads in the study area, typically two-lane highways or
roads with less improvement, were not absolute barriers to wolverine
movement. The individual wolverine that moved to Colorado from Wyoming
in 2008 successfully crossed Interstate 80 in southern Wyoming (Inman
et al. 2008, Figure 6). Wolverines in Norway successfully cross deep
valleys that contain light human developments such as railway lines,
settlements, and roads (Landa et al. 1998, p. 454). Wolverines in
central Idaho avoided portions of a study area that contained roads,
although this was possibly an artifact of unequal distribution of roads
that occurred at low elevations and peripheral to the study site
(Copeland et al. 2007, p. 2211). Wolverines frequently used un-
maintained roads for traveling during the winter, and did not avoid
trails used infrequently by people or active campgrounds during the
summer (Copeland et al. 2007, p. 2211).
At both a site-specific and landscape scale, wolverine natal dens
were located particularly distant from public (greater than 7.5 km (4.6
mi)) and private (greater than 3 km (1.9 mi)) roads (May 2007, pp. 14-
31). Placement of dens away from public roads (and away from associated
human-caused mortality) was a positive influence on successful
reproduction (May 2007, pp. 14-31). Predictive, broad-scale habitat
models, developed using historical records of wolverine occurrence,
indicated that roads were negatively associated with wolverine
occurrence (Rowland et al. 2003, p. 101). Although wolverines appear to
avoid transportation corridors in their daily movements, studies of the
few areas where transportation corridors are located in wolverine
habitat leads us to conclude that the effects are most likely local in
scale. There are no studies that address potential effects of
transportation corridors in linkage areas (i.e., outside of wolverine
habitat). In the few documented long-distance movements by wolverines,
the animals successfully crossed transportation corridors (Inman et al.
2009, Fig. 6). The available evidence indicates that dispersing
wolverines can successfully cross transportation corridors.
Land Management
Few effects to wolverines from land management actions such as
grazing,
[[Page 47539]]
timber harvest, and prescribed fire have been documented. Wolverines in
British Columbia used recently logged areas in the summer and moose
winter ranges for foraging (Krebs et al. 2007, pp. 2189-2190). Males
did not appear to be influenced strongly by the presence of roadless
areas (Krebs et al. 2007, pp. 2189-2190). In Idaho, wolverines used
recently burned areas despite the loss of canopy cover (Copeland 1996,
p. 124).
Intensive management activities such as timber harvest and
prescribed fire do occur in wolverine habitat; however, for the most
part, wolverine habitat tends to be located at high elevations and in
rugged topography that is unsuitable for intensive timber management.
Much of wolverine habitat is managed by the U.S. Forest Service or
other Federal agencies and is protected from some practices or
activities such as residential development. In addition, much of
wolverine habitat within the contiguous United States is already in a
management status such as wilderness or national park that provides
some protection from management, industrial, and recreational
activities. Wolverines are not thought to be dependent on specific
vegetation or habitat features that might be manipulated by land
management activities, nor is there evidence to suggest that land
management activities are a threat to the conservation of the DPS.
Summary of Factor A
At this time, we do not have sufficient information to make a
reliable prediction about how wolverines are likely to respond to the
effects of climate change. Wolverines have recently expanded in the
North Cascades and the northern Rocky Mountains from sources in Canada,
and are continuing to expand into suitable habitat not currently
occupied and/or occupied by a few individuals, including into Colorado,
California, Wyoming, and Utah. New information estimated that current
population size is approximately half of capacity (Inman et al. 2013),
confirming that continued population growth and expansion is possible
and even likely (Aubry et al. 2007, p. 2151).
There is strong support for the existence of an obligate
relationship between wolverines and deep spring snow at the den site.
However, available information suggests that availability of den sites
is not currently limiting wolverines, and we do not have sufficient
information to predict if and when this will occur in the future.
Furthermore, the importance of the relationship between wolverines and
snow at the broader home-range and DPS-range scales is uncertain. That
is, whether deep snow is required by wolverines outside of their needs
at the scale of the individual den site is not certain.
There is significant evidence that the climate within the range of
the wolverine is warming, which will likely impact both snowfall and
snow persistence. However, at this time, we do not have the sufficient
resolution of predictive climate models nor sufficient certainty in
those models and the results from them to make reasonably certain
conclusions about the specific response or sensitivity of wolverines to
predicted changes in amount and persistence of snowfall. Human
activities, including dispersed recreation activities, infrastructure,
and the presence of transportation corridors, occur in occupied
wolverine habitat. However, the alpine and subalpine habitats preferred
by wolverine typically receive little human use relative to lower
elevation habitats. The majority of wolverine habitat (over 90 percent)
occurs within U.S. Forest Service and National Park Service lands that
are subject to activities, but usually not direct habitat loss to
infrastructure development. The best available science leads us to
determine that human activities and developments do not pose a current
threat to wolverines in the contiguous United States.
Wolverines coexist with some modification of their environment, as
wilderness characteristics such as complete lack of motorized use or
any permanent human presence are likely not critical for maintenance of
populations. It is clear that wolverines coexist with some level of
human disturbance and habitat modification.
We know of no examples where human activities such as dispersed
recreation have occurred at a scale that could render a large enough
area unsuitable so that a wolverine home range would be likely to be
rendered unsuitable or unproductive. Given the large size of home
ranges used by wolverine, most human activities affect such a small
portion that negative effects to individuals are unlikely. These
activities do not occur at a scale that is likely to have population-
level effects to wolverine.
Little scientific or commercial information exists regarding
effects to wolverines from development or human disturbances associated
with them. What little information does exist suggests that wolverines
can adjust to moderate habitat modification, infrastructure
development, and human disturbance. In addition, large amounts of
wolverine habitat are protected from human disturbances and
development, either legally through wilderness and National Park
designation, or by being located at remote and high-elevation sites.
Therefore, wolverines are afforded a relatively high degree of
protection from the effects of human activities by the nature of their
habitat. Wolverines are known to successfully disperse long distances
between habitats through human-dominated landscapes and across
transportation corridors. The current level of residential, industrial,
and transportation development in the western United States does not
appear to have precluded the long-distance dispersal movements that
wolverines require for maintenance of genetic diversity. We do not have
information to suggest that future levels of residential, industrial,
and transportation development would be a significant conservation
concern for the DPS.
In summary, we do not have the sufficient information to make a
reliable prediction about how wolverines are likely to respond to
impacts to habitat that may result from climate change and whether such
habitat changes will pose a threat in the future. Additionally, the
best available scientific and commercial information does not indicate
that other potential stressors such as land management, recreation,
infrastructure development, and transportation corridors pose a threat
to the DPS.
Factor B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
Over much of recent history, trapping has been a primary cause of
wolverine mortality (Banci 1994, p. 108; Krebs et al. 2004, p. 497;
Lofroth and Ott 2007, pp. 2196-2197; Squires et al. 2007, p. 2217).
Unregulated trapping is believed to have played a role in the
historical decline of wolverines in North America in the late 1800s and
early 1900s (Hash 1987, p. 580). Wolverines are especially vulnerable
to targeted trapping and predator reduction campaigns due to their
habit of ranging widely in search of carrion, bringing them into
frequent contact with poison baits and traps (Copeland 1996, p. 78;
Inman et al. 2007a, pp. 4-10; Packila et al. 2007, p. 105; Squires et
al. 2007, p. 2219).
A study in British Columbia determined that, under a regulated
trapping regime, trapping mortality in 15 of 71 wolverine population
units was unsustainable, and that populations in those unsustainable
population units were dependent on immigration from neighboring
populations or untrapped refugia (Lofroth and Ott 2007, pp. 2197-2198).
Similarly, in southwestern Montana, legal trapping in isolated
[[Page 47540]]
mountain ranges accounted for 64 percent of documented mortality and
reduced the local wolverine subpopulation (Squires et al. 2007, pp.
2218-2219). The observed harvest levels, which included two pregnant
females in a small mountain range, could have significant negative
effects on a small subpopulation (Squires et al. 2007, p. 2219).
Harvest refugia, such as jurisdictions with closed seasons, national
parks, and large wilderness areas, are important to wolverine
persistence on the landscape because they can serve as sources of
surplus individuals to bolster trapped populations (Squires et al.
2007, p. 2219; Krebs and Ott 2004, p. 500). Due to their large space
requirements, wolverine population refuges must be large enough to
provide protection from harvest mortality, and complete protection is
only available for wolverines whose entire home range occurs within
protected areas. Glacier National Park, though an important refuge for
a relatively robust population of wolverines, was still vulnerable to
trapping because most resident wolverines' home ranges extended into
large areas outside the park (Squires et al. 2007, p. 2219). It is
likely that the larger scale refuges provided by the States of Idaho
and Wyoming (which do not permit wolverine trapping) provide wolverine
habitat that is fully protected from legal harvest in Montana; however,
wolverines with home ranges that partially overlap Montana and
dispersers that move into Montana would be vulnerable to harvest. Due
to the restrictive, low level of harvest now allowed by Montana, the
number of affected wolverines would be correspondingly small.
Despite the impacts of trapping on wolverines in the past, trapping
is no longer a risk factor within most of the wolverine's range in the
contiguous United States. Montana is the only State where wolverine
trapping is still legal. Before 2004, average wolverine harvest was
10.5 wolverines per year. Due to preliminary results of the study
reported in Squires et al. (2007, pp. 2213-2220), the Montana
Department of Fish, Wildlife, and Parks adopted new regulations for the
2004-2005 trapping season that divided the State into three units, with
the goal of spreading the harvest more equitably throughout the State.
For the 2008-2009 trapping season, the Montana Department of Fish,
Wildlife, and Parks adjusted its wolverine trapping regulations again
to further increase the geographic control on harvest to prevent
concentrated trapping in any single area, and to completely stop
trapping in isolated mountain ranges where small populations are most
vulnerable (Montana Department of Fish Wildlife and Parks 2010, pp. 8-
11). Their new regulations spread harvest across three geographic units
(the Northern Continental Divide area, the Greater Yellowstone area,
and the Bitterroot Mountains), and established a Statewide limit of
five wolverines. From 2008 until 2012 wolverine take averaged 3
wolverines annually (Montana Department of Fish Wildlife and Parks
2010, pp. 8-11; Brian Giddings 2012, pers. comm.), with reduced harvest
being due to season closure rather than lack of wolverines. The size of
the wolverine population subjected to trapping in this area is not
known precisely but is likely not more than about 300 animals in states
of Montana, Idaho, and Wyoming combined (Inman et al. 2013). On
November 30, 2012, a district court judge granted a temporary
restraining order that blocked the opening of Montana's wolverine
trapping season (Case No. BDV-2012-868). That restraining order remains
in place and the season remains closed.
The Montana Department of Fish, Wildlife, and Parks conduct yearly
furbearer monitoring using track surveys. These surveys involve
snowmobiling along transect routes under good tracking conditions and
visually identifying all carnivore tracks encountered. The protocol
does not use verification methods such as DNA collection or camera
stations to confirm identifications. Consequently, misidentifications
are likely to occur. Given the relative rarity of wolverines and the
relative abundance of other species with which they may be confused,
such as bobcats (Lynx rufus), Canada lynx (Lynx canadensis), and
mountain lions (Felis concolor), lack of certainty of identifications
of tracks makes it highly likely that the rare species is
overrepresented in unverified tracking records (McKelvey et al. 2008,
entire). The Montana Department of Fish, Wildlife, and Parks wolverine
track survey information does not meet our standard for reliability,
and we have not relied on this information in this analysis.
Montana wolverine populations have rebounded from historic lows in
the early 1900s while at the same time being subjected to regulated
trapping (Aubry et al. 2007, p. 2151; Montana Department of Fish,
Wildlife, and Parks 2007, p. 1). In fact, much of the wolverine
expansion that we have described above took place under less
restrictive (i.e., higher harvest levels) harvest regulations than are
in place today. The extent to which wolverine population growth has
occurred in Montana as a result of within-Montana population growth,
versus population growth attributable to surrounding States where
wolverines are not trapped (i.e., population growth driven by the
entire metapopulation versus just the portion of the metapopulation
found in Montana), is unknown.
We reviewed the current levels of incidental trapping (i.e.,
capture in traps set for species other than wolverine) and impacts on
wolverines. In the 2008-2009 trapping season, two wolverines were
incidentally killed in traps set for other species in Beaverhead and
Granite Counties, Montana (Montana Fish, Wildlife, and Parks 2010, p.
2). These two mortalities occurred within the portion of southwestern
Montana that is currently closed to legal wolverine trapping to ensure
that wolverines are not unsustainably harvested in this area of small,
relatively isolated mountain ranges. More recently, a wolverine was
trapped incidentally and released unharmed in December 2013, and
another was incidentally killed in January 2014 by a trap set for other
species (Giddings 2014, pers. comm.). Idaho Department of Fish and Game
records show that since 1965, 14 wolverines have been incidentally
trapped during the Idaho furbearer season, equating to an average of
0.29 wolverines incidentally trapped annually. Eight of these
incidental catches were released alive, and 6 resulted in confirmed
mortality. This count includes 4 wolverines incidentally trapped during
the 2013-2014 furbearer season (3 released alive; 1 mortality) (Idaho
Department of Fish and Game 2014, p. 26). The U.S. Department of
Agriculture's Wildlife Services trapped three wolverines (one each in
2004, 2005, and 2010) incidental to trapping wolves involved in
livestock depredations. One of these sustained severe injuries and was
euthanized. The other two were released without visible injury. Another
wolverine was trapped in Wyoming in 2006 outside of the expected range
for wolverine (Lanka 2014, pers. comm.). This animal was released
unharmed (Inman 2012, pers. comm.). The three documented mortalities
are possibly locally significant for wolverines in these areas because
local populations in each of the mountain ranges are small and
relatively isolated from nearby source populations.
Summary of Factor B
Legal wolverine harvest occurs in one state, Montana, within the
range of the DPS. The extent to which this harvest
[[Page 47541]]
affects populations occurring outside of Montana is unknown. However,
the State of Montana contains much of the habitat and wolverines that
exist in the current range of the DPS, and regulates trapping to reduce
the impact of harvest on wolverine populations. Incidental harvest also
occurs within the range of the DPS; however, the level of mortality
from incidental trapping appears to be low.
The current known level of incidental trapping mortality is low. We
note that it is unknown whether or not increased trapping of wolves
associated with wolf trapping regulations recently approved by the
States of Idaho and Montana would be likely to result in increased
incidental trapping of wolverines. Idaho began its wolf trapping
program in the winter of 2011-2012, and Montana began theirs in the
winter of 2012-2013. These wolf trapping activities are relatively new
in the DPS area, and we do not yet have reliable information on the
level of incidental take of wolverines that may result from them.
Based on the best scientific and commercial information available,
we conclude that trapping, including known rates of incidental trapping
in Montana and Idaho, result in a small number of wolverine mortalities
each year and that this level of mortality by itself is not a threat to
the wolverine DPS.
Factor C. Disease or Predation
No information is currently available on the potential effects of
disease on wild wolverine populations. Wolverines are sometimes killed
by wolves (Canis lupus), black bears (Ursus americanus), and mountain
lions (Burkholder 1962, p. 264; Hornocker and Hash 1981, p. 1296;
Copeland 1996, pp. 44-46; Inman et al. 2007d, p. 89). In addition,
wolverine reproductive dens are likely subject to predation, although
so few dens have been discovered in the contiguous U.S. that
determining the intensity of this predation is not possible.
Summary of Factor C
We have no information to suggest that wolverine mortality from
predation and disease is above natural or sustainable levels. The best
scientific and commercial information available indicates that disease
or predation is not a threat to the DPS now or likely to become so in
the future.
Factor D. Inadequacy of Existing Regulatory Mechanisms
Our interpretation of the Act for assessing regulatory mechanisms
under Factor D is to evaluate the inadequacy of existing regulatory
mechanisms in the context of how they address the threats identified
for the DPS or its habitat under Factors A, B, C, or E. Based on the
conclusion that effects related to climate change are not a threat, and
the fact that other threats cited in the proposed rule were considered
threats only in light of the effects of climate change, we have
determined that there are no threats to the wolverine under any of the
factors. There were two areas, however, where regulatory mechanisms
contributed to our conclusion that risk factors were not threats:
Regulations under the Wilderness Act and trapping regulations in
Montana.
The Wilderness Act
The U.S. Forest Service and National Park Service both manage lands
designated as wilderness areas under the Wilderness Act of 1964 (16
U.S.C. 1131-1136). Within these areas, the Wilderness Act states the
following: (1) New or temporary roads cannot be built; (2) there can be
no use of motor vehicles, motorized equipment, or motorboats; (3) there
can be no landing of aircraft; (4) there can be no other form of
mechanical transport; and (5) no structure or installation may be
built. A large amount of suitable wolverine habitat, about 28 percent
for the States of Montana, Idaho, and Wyoming, occurs within Federal
wilderness areas in the United States (Inman, 2007b, pers. comm.). As
such, a large proportion of existing wolverine habitat is protected
from direct loss or degradation by the prohibitions of the Wilderness
Act.
Wilderness areas provide protection to wolverines by making access
to wolverine habitats difficult, especially in winter. Wolverine
habitats are characterized by deep snow and cold conditions in the
winter time. Access to these areas is restricted to non-motorized
users. This makes it extremely difficult to pursue trapping activities
in wilderness that may purposefully target wolverines or incidentally
capture them.
Montana Trapping Regulations
Before 2004, the Montana Department of Fish, Wildlife, and Parks
regulated wolverine harvest through the licensing of trappers, a bag
limit of one wolverine per year per trapper, and no Statewide limit.
Under this management, average wolverine harvest was 10.5 wolverines
per year. Due to preliminary results of the study reported in Squires
et al. (2007, pp. 2213-2220), Montana Department of Fish, Wildlife, and
Parks adopted new regulations for the 2004-2005 trapping season that
divided the State into three units with the goal of spreading the
harvest more equitably among available habitat. In 2008, Montana
Department of Fish, Wildlife, and Parks further refined their
regulations to prohibit trapping in isolated mountain ranges, and
reduced the overall Statewide harvest to five wolverines with a
Statewide female harvest limit of three. Due to a court-issued
restraining order issued in November 2012, the Montana trapping season
on wolverines was blocked and remains closed. Under Factor B, above, we
concluded that trapping, including known rates of incidental trapping
in Montana and other parts of the DPS, is not a threat to the wolverine
DPS.
Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence
Small Population Size
Population ecologists use the concept of a population's
``effective'' size as a measure of the proportion of the actual
population that contributes to future generations (for a review of
effective population size, see Schwartz et al. 1998, entire). In a
population where all of the individuals contribute offspring equally,
effective population size would equal true population size, referred to
as the population census size. For populations where contribution to
the next generations is often unequal, effective population size will
be smaller than the census size. The smaller the effective population
size, the more reproduction in each generation is dominated by a few
individuals in each generation. For wolverines it is likely that
individuals occupying high-quality home ranges are better able to
reproduce. Therefore, mature males and females that are successful at
acquiring and defending a territory may dominate reproduction. Another
contributing factor that reduces effective population size is the
tendency in wolverines for a few males to monopolize the reproduction
of several females, reducing reproductive opportunities for other
males. Although this monopolization is a natural feature of wolverine
life-history strategy, it can lead to lower effective population size
and reduce population viability by reducing genetic diversity. The
effective population is not static; members of the effective population
in one year may lose this status in the following year and possibly
regain it again later depending on their reproductive success. When
members of the effective population are lost, it is likely that their
territories are quickly filled by younger individuals
[[Page 47542]]
who may not have been able to secure a productive territory previously.
Effective population size is important because it determines rates
of loss of genetic variation and the rate of inbreeding. Populations
with small effective population sizes show reductions in population
growth rates and increases in extinction probabilities when genetic
diversity is low enough to lead to inbreeding depression (Leberg 1990,
p. 194; Jimenez et al. 1994, pp. 272-273; Newman and Pilson 1997, p.
360; Saccheri et al. 1998, p. 492; Reed and Bryant 2000, p. 11;
Schwartz and Mills 2005, p. 419; Hogg et al. 2006, pp. 1495, 1498;
Allendorf and Luikart 2007, pp. 338-342). Franklin (1980, as cited in
Allendorf and Luikart 2007, p. 359) proposed an empirically based rule
suggesting that for short-term (a few generations) maintenance of
genetic diversity, effective population size should not be less than
50. For long-term (hundreds of generations) maintenance of genetic
diversity, effective population size should not be less than 500
individuals (for appropriate use of this rule and its limitations see
Allendorf and Luikart 2007, pp. 359-360); others propose that even
higher numbers are required. Each wolverine subpopulation within the
contiguous United States would need an estimated 400 breeding pairs, or
1 to 2 effective migrants per generation to meet this threshold
(Cegelski et al. 2006, p. 209). Long-term connectivity to the reservoir
of genetic resources in the Canadian population of wolverines will
likely be required for the long-term genetic health of the DPS (Traill
et al. 2010, p. 32; Allendorf and Luikart 2007, pp. 359-360). Since the
proposed rule published (February 4, 2013), Inman et al. (2013)
published an estimated available habitat capacity to be approximately
644 wolverines (95 percent CI = 506-1881) and estimated that current
population size is currently approximately half of capacity. Given the
life history of wolverines that includes high inequality of
reproductive success and a metapopulation of semi-isolated
subpopulations, effective population sizes would likely never reach
even 100 individuals at full habitat occupancy, as this would suggest a
census population of over 1,000. In this case, population connectivity
exchange with the larger Canadian/Alaskan population would likely be
required for long-term genetic health of the DPS.
Wolverine effective population size in the northern Rocky
Mountains, which is the largest extant population in the contiguous
United States, is low and is below what is thought necessary for short-
term maintenance of genetic diversity. Estimates for effective
population size for wolverines in the northern Rocky Mountains averaged
35 (credible limits = 28-52) (Schwartz et al. 2009, p. 3226). This
study excluded the small population from the Crazy and Belt Mountains
(hereafter ``CrazyBelts'') as they may be an isolated population, which
could bias the estimate using the methods of Tallmon et al. (2007,
entire). Measures of the effective population sizes of the other
populations in the contiguous United States have not been completed,
but given their small census sizes, their effective sizes are expected
to be smaller than for the northern Rocky Mountains population. Thus,
wolverine effective population sizes are very low. To date, no adverse
effects of the lower genetic diversity of the contiguous U.S. DPS of
wolverines have been documented. Therefore, we conclude that effective
population size estimates for wolverines do not suggest that small
population size is currently a threat to the DPS, but they do suggest
that populations are low enough that they could be vulnerable to loss
of genetic diversity in the future.
Wolverines in the contiguous United States are thought to be
derived from a recent recolonization event after they were extirpated
from the area in the early 20th century (Aubry et al. 2007, Table 1).
Consequently, wolverine populations in the contiguous United States
have reduced genetic diversity relative to larger Canadian populations
as a result of founder effects or inbreeding (Schwartz et al. 2009, pp.
3228-3230). Wolverine effective population size in the northern Rocky
Mountains was estimated to be 35 (Schwartz et al. 2009, p. 3226) and is
below what is thought to be adequate for short-term maintenance of
genetic diversity. Loss of genetic diversity can lead to inbreeding
depression and is associated with increased risk of extinction
(Allendorf and Luikart 2007, pp. 338-343). Small effective population
sizes are caused by small actual population size (census size), or by
other factors that limit the genetic contribution of portions of the
population, such as polygamous mating systems. Populations may increase
their effective size by increasing census size or by the regular
exchange of genetic material with other populations through
interpopulation mating.
The concern with the low effective population size was highlighted
in a recent analysis that determined that, without immigration from
other wolverine populations, at least 400 breeding pairs would be
necessary to sustain the long-term genetic viability of the northern
Rocky Mountains wolverine population (Cegelski et al. 2006, p. 197).
However, the entire population is likely only 250 to 300 (Inman 2010b,
pers. comm.), with a substantial number of these being unsuccessful
breeders or nonbreeding subadults (i.e., part of the census population,
but not part of the effective population).
Genetic studies demonstrate the essential role that genetic
exchange plays in maintaining genetic diversity in small wolverine
populations. Genetic drift has already occurred in subpopulations of
the contiguous United States: Wolverines here contained 3 of 13
haplotypes found in Canadian populations (Kyle and Strobeck 2001, p.
343; Cegelski et al. 2003, pp. 2914-2915; Cegelski et al. 2006, p. 208;
Schwartz et al. 2007, p. 2176; Schwartz et al. 2009, p. 3229). The
haplotypes found in these subpopulations were a subset of those in the
larger Canadian population, indicating that genetic drift had caused a
loss of genetic diversity. One study found that a single haplotype
dominated the northern Rocky Mountain wolverine population, with 71 of
73 wolverines sampled expressing that haplotype (Schwartz et al. 2007,
p. 2176). The reduced number of haplotypes indicates not only that
genetic drift has occurred but also some level of genetic separation;
if these populations were freely interbreeding, they would share more
haplotypes (Schwartz et al. 2009, p. 3229). The reduction of haplotypes
is likely a result of the fragmented nature of wolverine habitat in the
United States and is consistent with an emerging pattern of reduced
genetic variation at the southern edge of the range documented in a
suite of boreal forest carnivores (Schwartz et al. 2007, p. 2177).
However, as mentioned above, no adverse effects of the lower genetic
diversity of the contiguous U.S. DPS of wolverines have been
documented.
Immigration of wolverines from Canada is not likely to bolster the
genetic diversity of wolverines in the contiguous United States. There
is an apparent lack of connectivity between wolverine populations in
Canada and the United States based on genetic data (Schwartz et al.
2009, pp. 3228-3230). The apparent loss of connectivity between
wolverines in the northern Rocky Mountains and Canada prevents the
influx of genetic material needed to maintain or increase the genetic
diversity in the contiguous United States. The continued loss of
genetic diversity may lead to inbreeding depression, potentially
reducing the DPS ability to persist through reduced
[[Page 47543]]
reproductive output or reduced survival. Currently, the cause for this
lack of connectivity is uncertain. Wolverine habitat appears to be
well-connected across the border region (Copeland et al. 2010, Figure
2), and there are few manmade obstructions such as transportation
corridors or alpine developments. However, this lack of genetically
detectable connectivity may be related to harvest management in
southern Canada.
Summary of Factor E
Small population size and resulting inbreeding depression are
potential, though as-yet undocumented, threats to wolverines in the
contiguous United States. There is good evidence that genetic diversity
is lower in wolverines in the DPS than it is in the more contiguous
habitat in Canada and Alaska. The significance of this lower genetic
diversity to wolverine conservation is unknown. We do not discount the
possibility that loss of genetic diversity could be negatively
affecting wolverines now and could continue to do so in the future. It
is important to point out, however, that wolverine populations in the
DPS area are thought to be the result of colonization events that have
occurred since the 1930s. Such recent colonizations by relatively few
individuals and subsequent population growth are likely to have
resulted in founder effects, which could contribute to low genetic
diversity. The effect of small population sizes and low genetic
diversity may become more significant if populations become smaller and
more isolated.
Based on the best scientific and commercial information available
we conclude that demographic stochasticity and loss of genetic
diversity due to small effective population sizes is not a threat to
the wolverine DPS. In the proposed listing rule, we concluded that
demographic stochasticity and loss of genetic diversity due to small
effective population sizes were threats to wolverines only when
considered cumulatively with habitat loss due to climate change. Since
we no longer find that habitat loss due to climate change is a threat
to the wolverine DPS, we also no longer find that demographic
stochasticity and loss of genetic diversity due to small effective
population sizes are threats when considered cumulatively with habitat
loss due to climate change.
Synergistic Interactions Between Threat Factors
A species may be affected by more than one factor in combination.
Within the preceding review of the five threat factors, we discussed
potential threats that may have interrelated impacts on wolverines. Our
analysis did not find any significant effects to wolverines. However,
we recognize that multiple stressors acting in combination have greater
potential to affect wolverines than each source alone. Thus, we
consider how the combination of these stressors may affect wolverines.
In our proposed listing rule (74 FR 7885-7886), we identified
stressors that became threats to wolverines when operating in concert
with the effects of climate change. Those secondary threats included
genetic and demographic effects of small population size and the
effects of harvest, both intentional permitted trapping and incidental
trapping as non-target species. Given new information highlighting the
uncertainty of how the effects of climate change will impact the
wolverine DPS, we did not identify the effects of climate change as
posing a risk of extinction to the DPS, and, at this time, we therefore
conclude that the identified secondary factors do not rise to the level
of a threat to the DPS when considered in combination with the effects
of climate change. We are uncertain of how wolverines will respond to
the effects of climate change on their habitat and the resulting
population persistence, and do not conclude that demographic
stochasticity and loss of genetic diversity due to small population
size will be realized. Regarding harvest, we do not find the limited
legal harvest currently occurring in Montana (<= 5 animals per year) to
be a threat as the population appears to have continued to increase
while sustaining this level of legal take. Regarding incidental take
associated with legal harvest activities, we also do not find it rises
to the level of a threat to the DPS because documented incidental take
is extremely low and wolverines have seemingly increased with this
potential mortality source in existence. Wolverine populations have
been expanding in the DPS area since the early 20th century, when they
were likely at or near zero (Aubry et al. 2007, p. 2151). Given this
ongoing expansion in the DPS area and the lack of identified threats,
we do not find any combination of factors to be a threat at this time.
Determination
As required by the Act, we considered the five factors in assessing
whether the wolverine meets the definition of an endangered or a
threatened species. We examined the best scientific and commercial
information available regarding the present and future threats faced by
the DPS. Based on our review of the best available scientific and
commercial information, we find that the current and future factors
affecting the wolverine are not of sufficient imminence, intensity, or
magnitude to indicate that the wolverine is in danger of extinction
(endangered), or likely to become endangered within the foreseeable
future (threatened), throughout all or a significant portion of its
range. Therefore, the wolverine DPS does not meet the definition of an
endangered or a threatened species, and we are withdrawing the proposed
rule to list the wolverine as a threatened species. Our rationale for
this determination is outlined below.
Our proposed rule to list the wolverine as a threatened species
identified one primary threat to the wolverine (effects of climate
change on habitat) and other threats as secondary, only rising to the
level of a threat to the extent that they may work in concert with
climate change impacts to affect the status of the DPS. The reduction
of persistent spring snow due to climate change was cited as the
specific threat. The degree to which wolverine populations will be
impacted by a change in the amount or extent of deep snow limiting the
availability of year round habitat and den sites is the fundamental
question that informs whether the DPS is likely to become an endangered
species in the foreseeable future. Our original conclusion was that
such a change in climate would in fact cause habitat loss, den site
loss, and ultimately population impacts leading to the wolverine being
likely to become an endangered species within the foreseeable future.
After further consideration, and with input from peer review, public
comments, and the expert panel workshop, we no longer conclude that
impacts from climate change pose a risk of extinction to the wolverine
DPS for the following reasons:
(1) Considering all of the information we have received and
summarized, we have evidence that wolverines are expanding both within
the area currently inhabited by wolverines as well as into suitable
habitat not currently occupied and/or occupied with a few individuals.
Recent evidence suggests that there is suitable habitat available
within the contiguous United States to support a wolverine population
twice as large as that at present. Even under conditions of future
reduced snowpack as a consequence of climate change, sufficient habitat
will likely remain to maintin the wolverine population at the current
level of abundance.
[[Page 47544]]
(2) There is strong support for the existence of an obligate
relationship between wolverines and deep spring snow at the den site;
however, available information suggests that den sites are not
currently limiting wolverines, and we do not have sufficient
information to predict if and when any limitation will occur in the
future. Additionally, support for the obligate relationship between
wolverine and deep snow at an individual wolverine's home range or the
DPS' range in general is lacking. That is, we do not have evidence to
suggest that deep snow is required by wolverines throughout their home
ranges, beyond the level of the individual den site.
(3) There is significant evidence that the climate within the
larger range of the wolverine is warming, which will no doubt have
impacts on both snowfall and snow persistence. However, at this time,
we do not have sufficient resolution of predictive climate models nor
sufficient certainty in those models and the results from them to
understand the specific response or sensitivity of wolverines to
predicted changes in the amount and persistence of snowfall at the
scale of specific wolverine den sites. Uncertainties in the models, the
effects that could occur, and the potential associated responses in the
species include the following:
a. McKelvey et al. (2011) is the most sophisticated analysis of the
impacts of climate change at a scale specific to wolverine; however,
the scale is not fine enough to deal with the site specific
characteristics of wolverine dens.
b. Wolverine dens typically occur at high elevation and on north-
facing slopes. The conclusion of habitat loss for wolverines based on
loss of spring snow was based on analysis of snow at the overall range
of wolverine and did not scale down to areas specifically selected by
wolverines for den locations.
c. There is uncertainty in the ability of the models to predict
both snowfall amounts and/or persistence in areas most important for
critical wolverine life stages (i.e., denning).
d. Although snow cover may be reduced in the future, due to the
expansive home ranges of female wolverines and availability of multiple
potential den sites, there is no evidence to suggest that den sites for
wolverines will become a limiting factor in the foreseeable future.
e. It is possible that, in response to the effects of climate
change, subpopulations may become increasingly isolated from each other
in the future. However, wolverines are known to regularly move long
distances through unsuitable habitat, suggesting that individuals will
likely be able to maintain connectivity between occupied areas.
While we understand the basis of the predictions in the McKelvey et
al. (2011) model, for the reasons outlined in our analysis under Factor
A, we do not accept that a loss of snow across the range of the
wolverine will result in a commensurate reduction in suitable wolverine
habitat. Furthermore, due to the uncertainty of climate models, and the
fact that we do not have the fine-scale modeling available to make
accurate predictions about the continued availability of den sites, in
our best professional judgment, we no longer agree with the conclusion
about wolverine habitat loss that formed the basis of the proposed
rule. Although climate change effects are expected to result in the
loss of some wolverine habitat, we have no data to inform us as to
whether or how these projected effects may affect the viability of
wolverine populations. Our most recent review of the best available
information indicates that even in the face of the effects of climate
change, sufficient habitat will likely remain to support wolverines in
the contiguous U.S. at numbers at the very least roughly equal to those
estimated to exist today. Thus, even under future projected
environmental conditions, we do not have data to suggest that wolverine
populations in the contiguous United States are likely to experience
significant declines, such that they are likely to become in danger of
extinction within the foreseeable future. Accordingly, we no longer
find that listing the wolverine DPS as a threatened species is
warranted. We hereby withdraw the proposed rule to list the wolverine
DPS as a threatened species under the Act (78 FR 7864; February 4,
2013), and find that the DPS is not warranted for listing as endangered
or threatened. Accordingly, we also withdraw the associated proposed
rule under section 4(d) of the Act contained in the proposed listing
rule (78 FR 7864; February 4, 2013) and withdraw the proposed
nonessential population designation for the southern Rocky Mountains
States (78 FR 7890; February 4, 2013).
We will continue to monitor the status of the DPS and evaluate any
other information we receive. Additional information will continue to
be accepted on all aspects of the DPS. If at any time data indicate
that the protective status under the Act should be provided or if there
are new threats or increasing stressors that rise to the level of a
threat, we can initiate listing procedures, including, if appropriate,
emergency listing pursuant to section 4(b)(7) of the Act.
Significant Portion of the Range
Under the Act and our implementing regulations, a species may
warrant listing if it is an endangered or a threatened species
throughout all or a significant portion of its range. The Act defines
``endangered species'' as any species which is ``in danger of
extinction throughout all or a significant portion of its range,'' and
``threatened species'' as any species which is ``likely to become an
endangered species within the foreseeable future throughout all or a
significant portion of its range.'' The term ``species'' includes ``any
subspecies of fish or wildlife or plants, and any distinct population
segment [DPS] of any species of vertebrate fish or wildlife which
interbreeds when mature.'' We published a final policy interpretating
the phrase ``Significant Portion of its Range'' (SPR) (79 FR 37578).
The final policy states that (1) if a species is found to be an
endangered or a threatened species throughout a significant portion of
its range, the entire species is listed as an endangered or a
threatened species, respectively, and the Act's protections apply to
all individuals of the species wherever found; (2) a portion of the
range of a species is ``significant'' if the species is not currently
an endangered or a threatened species throughout all of its range, but
the portion's contribution to the viability of the species is so
important that, without the members in that portion, the species would
be in danger of extinction, or likely to become so in the foreseeable
future, throughout all of its range; (3) the range of a species is
considered to be the general geographical area within which that
species can be found at the time FWS or NMFS makes any particular
status determination; and (4) if a vertebrate species is an endangered
or a threatened species throughout an SPR, and the population in that
significant portion is a valid DPS, we will list the DPS rather than
the entire taxonomic species or subspecies.
The SPR policy is applied to all status determinations, including
analyses for the purposes of making listing, delisting, and
reclassification determinations. The procedure for analyzing whether
any portion is an SPR is similar, regardless of the type of status
determination we are making. The first step in our analysis of the
status of a species is to determine its status throughout all of its
range. If we determine that the species is in danger of extinction, or
likely to become so in
[[Page 47545]]
the foreseeable future, throughout all of its range, we list the
species as an endangered (or threatened) species and no SPR analysis
will be required. If the species is neither an endangered nor a
threatened species throughout all of its range, we determine whether
the species is an endangered or a threatened species throughout a
significant portion of its range. If it is, we list the species as an
endangered or a threatened species, respectively; if it is not, we
conclude that listing the species is not warranted.
When we conduct an SPR analysis, we first identify any portions of
the species' range that warrant further consideration. The range of a
species can theoretically be divided into portions in an infinite
number of ways. However, there is no purpose to analyzing portions of
the range that are not reasonably likely to be significant and either
an endangered or a threatened species. To identify only those portions
that warrant further consideration, we determine whether there is
substantial information indicating that (1) the portions may be
significant and (2) the species may be in danger of extinction in those
portions or likely to become so within the foreseeable future. We
emphasize that answering these questions in the affirmative is not a
determination that the species is an endangered or a threatened species
throughout a significant portion of its range--rather, it is a step in
determining whether a more detailed analysis of the issue is required.
In practice, a key part of this analysis is whether the threats are
geographically concentrated in some way. If the threats to the species
are affecting it uniformly throughout its range, no portion is likely
to warrant further consideration. Moreover, if any concentration of
threats apply only to portions of the range that clearly do not meet
the biologically based definition of ``significant'' (i.e., the loss of
that portion clearly would not be expected to increase the
vulnerability to extinction of the entire species), those portions will
not warrant further consideration.
If we identify any portions that may be both (1) significant and
(2) endangered or threatened, we engage in a more detailed analysis to
determine whether these standards are indeed met. The identification of
an SPR does not create a presumption, prejudgment, or other
determination as to whether the species in that identified SPR is an
endangered or a threatened species. We must go through a separate
analysis to determine whether the species is an endangered or a
threatened species in the SPR. To determine whether a species is an
endangered or a threatened species throughout an SPR, we will use the
same standards and methodology that we use to determine if a species is
an endangered or a threatened species throughout its range.
Depending on the biology of the species, its range, and the threats
it faces, it may be more efficient to address the ``significant''
question first, or the status question first. Thus, if we determine
that a portion of the range is not ``significant,'' we do not need to
determine whether the species is an endangered or a threatened species
there; if we determine that the species is not an endangered or a
threatened species in a portion of its range, we do not need to
determine if that portion is ``significant.''
We evaluated the current range of the distinct population segment
of the North American wolverine to determine if there is any apparent
geographic concentration of potential threats for the DPS. We examined
potential threats due to human use and disturbance of habitat,
trapping, and effects of climate change. We found no concentration of
threats that suggests that the DPS of North American wolverine may be
in danger of extinction in a portion of its range. We found no portions
of the range where potential threats are significantly concentrated or
substantially greater than in other portions of the range. Therefore,
no portion of the range of the DPS of North American wolverine warrants
further consideration of possible endangered or threatened species
status under the Act.
References Cited
A complete list of references cited in this rulemaking is available
on the Internet at http://www.regulations.gov and upon request from the
Montana Ecological Services Office (see FOR FURTHER INFORMATION
CONTACT).
Authors
The primary authors of this final rule are the staff members of the
Montana Ecological Services Field Office and the Idaho Field Office
(see FOR FURTHER INFORMATION CONTACT).
Authority
The authority for this action is the Endangered Species Act of
1979, as amended (16 U.S.C. 1531 et seq.).
Dated: August 4, 2014.
Daniel M. Ashe,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2014-18743 Filed 8-12-14; 4:15 pm]
BILLING CODE 4310-55-P