[Federal Register: September 29, 2005 (Volume 70, Number 188)]
[Proposed Rules]               
[Page 56880-56884]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Revised 12-Month 
Finding for the Southern Rocky Mountain Distinct Population Segment of 
the Boreal Toad (Bufo boreas boreas)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of revised 12-month finding for the Southern Rocky 
Mountain Distinct Population Segment of the Boreal Toad.


SUMMARY: We, the Fish and Wildlife Service (Service), announce our 
revised 12-month finding for a petition to list the Southern Rocky 
Mountain population (SRMP) of the boreal toad (Bufo boreas boreas) as 
endangered under the Endangered Species Act (ESA). After a review of 
the best available scientific and commercial information, we find that 
listing is not warranted at this time because the SRMP of the boreal 
toad does not constitute a species, subspecies, or distinct population 
segment (DPS) under the ESA. Therefore, we withdraw the SRMP from the 
candidate list. The Service will continue to seek new information on 
the taxonomy, biology, and ecology of these toads, as well as potential 
threats to their continued existence.

DATES: This finding was made on September 20, 2005. Although no further 
action will result from this finding, we request that you submit new

[[Page 56881]]

information concerning the taxonomy, biology, ecology, and status of 
the SRMP or other populations of the subspecies, as well as potential 
threats to their continued existence, whenever it becomes available.

ADDRESSES: The complete file for this finding is available for 
inspection, by appointment, during normal business hours, at the U.S. 
Fish and Wildlife Service Ecological Services Field Office, 764 Horizon 
Drive, Building B, Grand Junction, Colorado 81506-3946. Submit new 
information, materials, comments, or questions concerning this species 
to us at the above address.

FOR FURTHER INFORMATION CONTACT: Allan Pfister, Western Colorado 
Supervisor, at the address listed above, by telephone at 970-243-2778, 
extension 29, by facsimile at 970-245-6933, or by e-mail 



    Section 4(b)(3)(B) of the ESA requires that within 12 months after 
receiving a petition to revise the List of Endangered and Threatened 
Wildlife that contains substantial information indicating that the 
petitioned action may be warranted, the Secretary shall make one of the 
following findings: the petitioned action is not warranted, the 
petitioned action is warranted, or the petitioned action is warranted 
but precluded by other pending proposals of higher priority. Such 12-
month findings are to be published promptly in the Federal Register. 
The ESA also requires that when a warranted but precluded finding is 
made, a petition is treated as resubmitted and the Service is required 
to publish a new petition finding on an annual basis.
    On September 30, 1993, the Service received a petition from the 
Biodiversity Legal Foundation, Boulder, Colorado, and Dr. Peter 
Hovingh, a researcher at the University of Utah, Salt Lake City, Utah. 
The petitioners requested that the Service list the SRMP of the 
``western boreal toad'' (Bufo boreas boreas) as endangered throughout 
its range in northern New Mexico, Colorado, and southern Wyoming, as 
well as designate critical habitat in all occupied areas and in the key 
unoccupied areas where restoration is necessary. A notice of a 90-day 
finding for the petition was published in the Federal Register on July 
22, 1994 (59 FR 37439), indicating that the petition and other readily 
available scientific and commercial information presented substantial 
information that the petitioned action may be warranted.
    In 1994, a Boreal Toad Recovery Team (Team) was formed of agency 
representatives from the Service, Colorado Division of Wildlife, 
Wyoming Game and Fish Department, New Mexico Department of Game and 
Fish, National Park Service, U.S. Geological Survey, U.S. Environmental 
Protection Agency, U.S. Forest Service, and U.S. Bureau of Land 
Management, along with technical advisors from several universities and 
other interested parties. The Team produced a recovery plan for the 
boreal toad in Colorado, a draft Conservation Strategy, and a draft 
Conservation Agreement; in 1998, components of these documents were 
combined in the production of the Boreal Toad Conservation Plan, which 
has since been revised (Loeffler 2001). Management activities guided by 
the Team include annual monitoring of known breeding populations; 
research of factors limiting toad survival; research of toad habitat, 
biology, and ecology; captive breeding and rearing techniques and 
protocols; experimental reintroductions of toads to vacant historic 
habitat; coordination with land management agencies, land use planners, 
and developers to protect the boreal toad and its habitats; and efforts 
to increase public education and awareness of the subspecies.
    On March 23, 1995, the Service announced a 12-month finding that 
listing the SRMP of the boreal toad (Bufo boreas boreas) as an 
endangered species was warranted but precluded by other higher priority 
actions (60 FR 15281). When we find that a petition to list a species 
is warranted but precluded, we refer to it as a candidate for listing. 
Section 4(b)(3)(B) of the ESA directs that, when we make a ``warranted 
but precluded'' finding on a petition, we are to treat the petition as 
being one that is resubmitted annually on the date of the finding; thus 
the ESA requires us to reassess the petitioned actions and to publish a 
finding on the resubmitted petition on an annual basis. Several 
candidate assessments for the boreal toad have been completed; these 
are available for viewing online at http: //http://www.fws.gov/endangered/candidates/index.html.
 The most recent assessment was published in the 

Federal Register May 11, 2005 (70 FR 24870).
    In our most recent Notice of Findings on Resubmitted Petitions, we 
noted that a proposed listing determination for the boreal toad would 
be funded in Fiscal Year 2005 (70 FR 24870, May 11, 2005). This 
resubmitted 12-month finding evaluates new information and re-evaluates 
previously acquired information. In accordance with section 4(b)(3)(B) 
of the ESA, we have now completed a status review of the best available 
scientific and commercial information on the species, and have reached 
a determination regarding the petitioned action.

Species Information

    The western toad (Bufo boreas) is an amphibian that occurs 
throughout much of the western United States. The species was first 
described by Baird and Girard (1852). Camp (1917) considered two forms 
as subspecies, the boreal toad (B. b. boreas) and the California toad 
(B. b. halophilus). Stebbins (1985) recognizes these two subspecies. 
Crother et al. (2003) note the general recognition of two nominal 
subspecies (B. b. boreas and B. b. halophilus), with the Amargosa toad 
(B. b. nelsoni) sometimes recognized as a third subspecies. Stebbins 
(1985) considers the Amargosa toad (Bufo nelsoni) to be a distinct 
species. The geographic variation within Bufo boreas is poorly studied 
and may mask a number of cryptic species (Crother et al. 2003). Recent 
DNA (deoxyribonucleic acid) analyses suggest a taxonomic change to the 
complex may be warranted (Goebel 1996).
    The range of the boreal toad subspecies (B. b. boreas) is coastal 
Alaska south through British Columbia, western Alberta, Washington, 
Oregon, northern California, western and central Nevada, Idaho, western 
Montana, western and south central Wyoming, the mountains of Utah and 
Colorado, and extreme northern New Mexico. The range of the California 
toad subspecies (B. b. halophilus) is northern California south to the 
Baja peninsula of Mexico, and east to western Nevada. The ranges of the 
California toad and the boreal toad overlap in northern California 
(Stebbins 1985). The SRMP of the boreal toad (B. b. boreas) is the 
segment of the subspecies that is the focus of this finding, and refers 
to the toads occurring within the southern Rocky Mountain physiographic 
province. This region extends from south central Wyoming, throughout 
the mountainous portions of Colorado, and into extreme northern New 
    Boreal toads in the SRMP may reach a length (snout to vent) of 11 
centimeters (4 inches) (Hammerson 1999). They possess warty skin, oval 
parotid glands, and often have a distinctive light mid-dorsal stripe. 
During the breeding season, males develop a dark patch on the inner 
surface of the innermost digit. Unlike other Bufo species, the boreal 
toad has no vocal sac and, therefore, no mating call (Hammerson 1999). 
Tadpoles are black or dark brown. The eggs are black

[[Page 56882]]

and are deposited in long double layer jelly strings with one to three 
rows of eggs (Hammerson 1999).
    In the southern Rocky Mountains, adult boreal toads emerge from 
winter refugia when snowmelt has cleared an opening from their burrows 
and daily temperatures remain above freezing (Campbell 1970a, b). 
Breeding occurs during a 2- to 4-week period from mid-May to mid-June 
at lower elevations, and as late as mid-July at higher elevations 
(Hammerson 1999). Suitable breeding sites are large bodies of water or 
small pools, beaver ponds, glacial kettle ponds, roadside ditches, 
human-made ponds, and slow-moving streams (Campbell 1970a; Hammerson 
    Females lay up to 16,500 eggs in 2 strings, which ordinarily are 
deposited in shallow water (Stebbins 1954). Carey et al. (2005) 
reported an overall mean clutch size of 6,661 eggs for 3 populations 
studied in Colorado. Eggs hatch 1 to 2 weeks after being laid. Egg and 
tadpole development is temperature-dependent, and reproductive efforts 
may fail if tadpoles do not have sufficient time to metamorphose before 
the onset of winter. Persistent, shallow bodies of water are critical 
to breeding success, and if the breeding site dries before 
metamorphosis is complete, desiccation of the tadpoles or eggs will 
occur. Tadpoles typically metamorphose by late July to late August, but 
at higher elevations metamorphosis may not be complete until late 
September (Loeffler 2001). Recently metamorphosed toadlets aggregate 
within a few meters of the water, and move into nearby moist habitats 
later in summer. After mating, adults often disperse to upland, 
terrestrial habitats, where they are mostly diurnally active in early 
and late summer (Mullally 1958; Campbell 1970a; Carey 1978), foraging 
primarily on ants, beetles, spiders, and other invertebrates 
(Schonberger 1945; Campbell 1970a). Late in the summer home ranges will 
expand, generally in the direction of wintering habitats (Campbell 
1970a), which include cavities among streamside boulders, ground 
squirrel burrows, and beaver lodges and dams (Hammerson 1999).
    Survival of embryos from laying to hatching is normally high but 
catastrophic mortality has been observed (Blaustein and Olson 1991). 
Survival of tadpoles and juveniles is very low, with predation and 
adverse environmental conditions primarily responsible for mortality at 
these life stages (Campbell 1970a). Samollow (1980) estimated that 95 
to 99 percent die before reaching their second year of life. The 
minimum age of breeding boreal toads in Colorado is about 4 years in 
males and 6 years in females (Hammerson 1999). Olson (1991) found that 
females may skip 1 to 3 years between breeding attempts. Individuals 
may live approximately 11 or 12 years (Olson 1991).

Distinct Vertebrate Population Segment

    Pursuant to the ESA, we must consider for listing any species, 
subspecies, or, for vertebrates, any DPS of these taxa if there is 
sufficient information to indicate that such action may be warranted. 
To interpret and implement the DPS provision of the ESA and 
congressional guidance, the Service and the National Marine Fisheries 
Service published, on December 21, 1994, a draft Policy Regarding the 
Recognition of Distinct Vertebrate Population Segments Under the ESA 
and invited public comments on it (59 FR 65885). After review of 
comments and further consideration, the Services adopted the 
interagency policy as issued in draft form, and published it in the 
Federal Register on February 7, 1996 (61 FR 4722). This policy 
addresses the recognition of DPSs for potential listing actions. The 
policy allows for more refined application of the ESA that better 
reflects the biological needs of the taxon being considered, and avoids 
the inclusion of entities that do not require its protective measures.
    Under our DPS policy, three elements are considered in a decision 
regarding the status of a possible DPS as endangered or threatened 
under the ESA. These are applied similarly for additions to the list of 
endangered and threatened species, reclassification, and removal from 
the list. They are: discreteness of the population segment in relation 
to the remainder of the taxon; the significance of the population 
segment to the taxon to which it belongs; and the population segment's 
conservation status in relation to the ESA's standards for listing 
(i.e., is the population segment, when treated as if it were a species, 
endangered or threatened?). Discreteness refers to the isolation of a 
population from other members of the species and we evaluate this based 
on specific criteria. If a population segment is considered discrete, 
the Service must consider whether the discrete segment is 
``significant'' to the taxon to which it belongs. We determine 
significance by using the best available scientific information to 
determine the DPS's importance to the taxon to which it belongs. If we 
determine that a population segment is discrete and significant, we 
then evaluate it for endangered or threatened status based on the ESA's 
standards. The DPS evaluation in this finding concerns the SRMP segment 
of the boreal toad subspecies (B. b. boreas), occurring within the 
southern Rocky Mountain physiographic province extending from south 
central Wyoming through the mountainous portions of Colorado and into 
extreme northern New Mexico.


    Under our DPS Policy, a population segment of a vertebrate species 
may be considered discrete if it satisfies either one of the following 
conditions: it is markedly separated from other populations of the same 
taxon as a consequence of physical, physiological, ecological, or 
behavioral factors (quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation); or it is 
delimited by international governmental boundaries within which 
differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the ESA. The SRMP meets 
the first condition for the following reasons:
    Based on evidence of feasible dispersal distances, the SRMP is 
geographically (physically) separated from other populations of the 
boreal toad (Keinath and McGee 2005). The greatest recorded distance of 
movement for a boreal toad in the southern Rocky Mountains is 8 
kilometers (5 miles) (Lambert 2003) and most movements are smaller 
(Bartelt 2000; Jones 2000; Muths 2003). Southern Wyoming toads (within 
the SRMP) are separated from the northern Wyoming populations (outside 
the SRMP) by approximately 160 kilometers (100 miles) of dry, non-
forested valleys and basins of the Red Desert (Keinath and McGee 2005). 
The boreal toad has never been observed in the Red Desert, and its 
highest elevations (2,000 m (6,562 ft)) are below the lowest elevation 
(2,300 m (7,546 ft)) of boreal toad occurrences in Wyoming. The habitat 
in riparian areas along rivers at these lower elevations is warmer, 
drier, and composed of much different vegetation, creating a barrier to 
migrating boreal toads (Keinath and McGee 2005). The large size and 
arid, inhospitable habitat make the Red Desert impassible for migrating 
toads. The SRMP also is geographically separated from other boreal toad 
populations to the west. Over 250 kilometers (155 miles) of arid 
habitat exists in eastern Utah and northwestern Colorado, physically 
separating the

[[Page 56883]]

SRMP from the Utah populations in the Wasatch and Uinta Mountains.
    Morphological differences between toads of the SRMP and other 
boreal toad populations provide evidence of the geographic separation 
of the SRMP. Burger and Bragg (1947) noted several morphological 
differences between adults collected in Colorado and the Pacific 
Northwest, including differences in body length, skin coloration and 
texture, head proportion, and parotid gland shape and position. In the 
former, the dorsal coloration is darker and the skin between the warts 
is smoother and less pronounced. In the Colorado toads, the parotid 
gland is more oblong and less elevated, ventral markings are more 
numerous and irregular, and the head is proportionately larger and 
broader. The maximum length of the Colorado toads was 8.3 centimeters 
(3.3 inches) compared with 12.5 centimeters (4.9 inches) in the Pacific 
Northwest toads (Burger and Bragg 1947). However, these observations 
were based on cursory examination of a few specimens from one Colorado 
geographic area, and many more specimens and observations of the boreal 
toad throughout its range were deemed necessary to clarify the status 
of the Colorado toads (Burger and Bragg 1947). Hubbard (1972) also 
noted morphological differences between boreal toads in Colorado and 
British Columbia, Canada, as well as behavioral and biochemical 
differences. British Columbia toads were observed to possess much 
brighter and more variable coloration, and a smaller parotid gland than 
Colorado specimens; the distress call of toads in Colorado did not have 
a decrease in frequency of terminal segments of harmonics, which toads 
in British Columbia possess; and a serum protein analysis indicated 
toads from British Columbia have greater proportions of alpha-2 
globulin and albumin and less alpha-1 globulin than those from Colorado 
(Hubbard 1972). However, comparisons of these characters within and 
between several additional boreal toad populations would be necessary 
to further substantiate the distinctiveness of toads in Colorado and 
the remainder of the SRMP.
    Based on its current geographic (physical) separation from other 
boreal toad populations, and some morphological and genetic 
differences, we conclude the SRMP meets the definition of discreteness 
under our DPS policy.


    If a population segment is determined to be discrete, the Service 
considers the available scientific evidence of its significance to the 
taxon to which it belongs. Our policy states that this consideration 
may include, but is not limited to, the following:
    (1) Persistence of the discrete population segment in an ecological 
setting unusual or unique for the taxon;
    (2) Evidence that loss of the discrete population segment would 
result in a significant gap in the range of the taxon;
    (3) Evidence that the discrete population segment represents the 
only surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historical range; or
    (4) Evidence that the discrete population segment differs markedly 
from other populations of the species in its genetic characteristics.
    A population segment needs to satisfy only one of these criteria to 
be considered significant. Furthermore, the list of criteria is not 
exhaustive; other criteria may be used, as appropriate.
    Persistence of the Discrete Population Segment in an Ecological 
Setting Unusual or Unique for the Taxon --The boreal toad occurs from 
the Rocky Mountains to the Pacific Coast. Throughout its range, the 
subspecies shows an unusual plasticity in its choice of habitats 
(Campbell 1970a). In the SRMP, toads inhabit montane wetland habitats 
and adjacent uplands near suitable breeding habitats. These are 
ecological settings similar to those used by populations of the boreal 
toad outside the SRMP, in the montane regions of northern Wyoming, 
Idaho, Utah, Montana, and other western states. Generally speaking, in 
the higher latitudes of its range suitable boreal toad habitats may be 
found at lower elevations. We do not find that the SRMP persists in an 
ecological setting unusual or unique for the subspecies.
    Loss Would Represent a Significant Gap in the Range of the Taxon--
Loss of the SRMP would reduce the range of B. b. boreas at its 
southeastern-most extension, from south central Wyoming, through the 
mountainous regions of Colorado, and into extreme northern New Mexico. 
The remaining range would extend from coastal Alaska south through 
British Columbia, western Alberta, Washington, Oregon, northern 
California, western and central Nevada, Idaho, western Montana, Utah, 
and western Wyoming. Due to the broad geographic range of B. b. boreas 
across the western United States, the gap resulting from loss of the 
SRMP would be a relatively small proportion of the overall subspecies 
range and not significant.
    Our analysis used the currently accepted taxonomy and range 
determinations for the parent taxon (the B. b. boreas subspecies) and 
the population segment under consideration (the SRMP). At this time, 
uncertainty exists with regard to the taxonomy of the Bufo boreas 
complex, including the designation of a single boreal toad subspecies, 
the distinctness of the SRMP segment, and the taxonomic status of other 
population segments in the Rocky Mountains. The geographic variation 
within Bufo boreas is poorly studied, and this lack of information is 
thought to mask the existence of other species (Crother et al. 2003). 
The results from phylogenetic analyses of the Bufo boreas group confirm 
this uncertainty, as they suggest the existence of evolutionary 
lineages inconsistent with the current taxonomy (Goebel 1996, 2005).
    If new taxonomic information becomes available that could change 
our analysis, we will reconsider our decision. However, based on the 
best available information, we cannot conclude at this time that loss 
of the SRMP would represent a significant gap in the range of the 
    The Only Surviving Natural Occurrence of a Taxon--This criterion 
from the DPS policy does not apply because the SRMP of the boreal toad 
is clearly not a ``population segment representing the only surviving 
natural occurrence of a taxon that may be more abundant elsewhere as an 
introduced population outside its historic range.'' If this situation 
changes or new information becomes available, we will reconsider our 
    Evidence that the SRMP Differs Markedly from Other Populations in 
Genetic Characteristics--In our consideration of ``significance,'' the 
Service must evaluate evidence to determine whether the SRMP differs 
markedly from other populations belonging to the currently recognized 
subspecies, B. b. boreas. Information from mitochondrial DNA data 
(Goebel 1996, 1999, 2000, 2003, 2005) and nuclear DNA data (Goebel 
1999, 2000, 2003) suggests that boreal toads of the SRMP differ 
genetically from other populations, but the differences between the 
SRMP and toads in central and northern Utah, southeastern Idaho, and 
western Wyoming are small, not well resolved, and based on small sample 
    A notable result of the mitochondrial DNA studies is that, in each 
study, specimens sampled from the SRMP cluster within the same 
phylogeographic clade, which is a group considered to be of common 
evolutionary origin. However, the specimens from the SRMP did not form

[[Page 56884]]

a monophyletic clade; depending on the study or analysis method, 
specimens from northern Utah, central Utah, and western Wyoming group 
with the SRMP (Goebel 1996, 1999, 2000, 2003, 2005). The lack of 
observed monophyly may be due to poor resolution that additional 
samples and sequence data might improve (Goebel 1999, 2000). It may 
also suggest that toads in the SRMP are very closely related to nearby 
populations due to recent (in geologic time) geographic isolation of 
the SRMP (Goebel 1999). While the current mitochondrial DNA data 
suggest the existence of diverging evolutionary lineages in the Bufo 
boreas group, the toads appear to be so closely related that 
interbreeding would likely produce viable offspring (Goebel 2003).
    The close relationships between the SRMP and nearby populations may 
also be due to the retention of ``old'' haplotypes from lineage sorting 
(Goebel 1999, 2000). From a phylogenetic viewpoint the entire 
mitochondrial DNA genome constitutes a single locus inherited as a 
linked unit (Avise 2000). Therefore, analyses based on the 
mitochondrial genome could produce patterns that represent the gene's 
lineage, but not necessarily the true evolutionary direction of the 
species. For this reason, when analyzing the historical relationships 
among taxa it is prudent to compare phylogenetic hypotheses from both 
mitochondrial data and nuclear data (which represent a large number of 
    Studies of the Bufo boreas group using nuclear DNA data have been 
performed, but the results were affected by small sample sizes from 
some localities and exclusion of samples due to missing data (Goebel 
1999, 2000). When later analyses were performed with additional 
samples, a nuclear DNA clade containing the SRMP was identified, but it 
included specimens from western Wyoming localities geographically 
separated from the SRMP (Goebel 2003).
    We believe that additional nuclear (e.g. micro satellite) DNA data 
and supplemental mitochondrial DNA sequence data are necessary to 
clarify the genetic relationships within and between boreal toad 
populations, including the SRMP segment and others in the Rocky 
Mountains. The multi-agency Team also recommends additional studies, on 
the grounds that genetic distinctions between SRMP toads and nearby 
toad populations are based on data from too few specimens (Loeffler 
2001). After considering the best available information, we cannot 
conclude that the SRMP differs markedly from other boreal toad 
populations in genetic characteristics.
    In conclusion, we determine that the SRMP, as currently described, 
does not meet the significance criteria of our DPS policy. As such, the 
SRMP does not qualify as a distinct population segment. Therefore, it 
is not a listable entity under the ESA. Based on this determination, we 
withdraw the SRMP from the candidate list.
    We will accept additional information and comments from all 
concerned governmental agencies, the scientific community, industry, or 
any other interested party concerning this finding. We will reconsider 
this determination in the event that new information indicates that the 
SRMP is significant.


    A complete list of all references cited herein is available upon 
request from the Grand Junction, Colorado Office, U.S. Fish and 
Wildlife Service (see ADDRESSES).


    The primary author of this finding is Larry Thompson, Grand 
Junction, Colorado Office, U.S. Fish and Wildlife Service (see 

    Authority: The authority for this action is the Endangered 

Species Act of 1973 (16 U.S.C. 1531 et seq.).

    Dated: September 20, 2005.
Marshall P. Jones, Jr.,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 05-19488 Filed 9-28-05; 8:45 am]