Lake Erie Watersnake (Nerodia sipedon insularum)
5-Year Review: Summary and Evaluation
Below are the General Information, Synthesis, and Results portions of the Five-Year Review. Go here for the complete 23-page Review (PDF).
Biologist Angie Boyer is holding a Lake Erie water snake during one of the annual surveys.
Photo by USFWS |
1.0 GENERAL INFORMATION
1.1 Reviewers
Lead Regional Office:
Carlita Payne, Midwest Region, Fort Snelling, MN (612) 713-5339
Lead Field Office:
Megan Seymour, Ohio Ecological Services Field Office (614) 416-8993, ext.16
Cooperating Field Office(s): none
Cooperating Regional Office(s): none
1.2 Methodology used to complete the review: This 5-year review was completed by Megan Seymour, Wildlife Biologist with the Ohio
Ecological Services Field Office, and recovery coordinator for the Lake Erie Watersnake
(Nerodia sipedon insularum). The Service requested new scientific or commercial data
and information that may have a bearing on the species' classification of threatened status
through a April 22, 2008, Federal Register notice (73 FR 21643) initiating the 5-year
review. The primary data used to conduct this 5-year review include various annual
reports from Dr. Richard King, Northern Illinois University (NIU), a recognized Lake
Erie Watersnake expert, Principal Investigator for the annual Lake Erie Watersnake
census, and generator of annual population estimates. Additional information was
obtained from Kristin Stanford, a Ph.D. candidate under Dr. King. Ms. Stanford
conducts research on various aspects of Lake Erie Watersnake biology and behavior, and
conducts significant public outreach efforts among island residents and visitors on the
U.S. western Lake Erie islands. Information on public opinion was derived primarily
from formal surveys conducted by Wayne Wilkinson, NIU (Wilkinson 2008) and Andrea
Olive (Olive 2008). Information on accidental human-induced mortality was obtained
from research conducted by NIU and The Ohio State University. Contaminant research
was conducted by Fernie et al. (2008). Research on the impacts of invasive species was
primarily completed by faculty and students at NIU (Jones et al. 2009, King et al. 2008,
King et al. 2006). The final listing rule (52 FR 21478) and the species recovery plan
(USFWS 2003) were also relied upon to evaluate if and to what degree each of the
recovery criteria identified in the Lake Erie Watersnake Recovery Plan (USFWS 2003)
has been achieved, and follow-up actions that may be warranted, while assessing the
species status in this 5-year review.
In the recovery plan (Service 2003a, p. G-19) we
describe a revision to the common name from “Lake Erie water snake” to “Lake Erie
Watersnake” per the peer-reviewed naming convention outlined in “Scientific and
Standard English Names of Amphibians and Reptiles of North America North of Mexico,
with Comments Regarding Confidence in Our Understanding” (most recent version
Crother 2008). Subsequently, we refer to the subspecies as “Lake Erie Watersnake” in
this and future documents.
In accordance with the 5-Year Review Guidance (USFWS and NMFS 2006), peer
review will be conducted when the proposed rule to remove the species from the List of
Endangered Species (50 CFR 17.11) is issued.
1.3 Background:
1.3.1 FR Notice citation announcing initiation of this review: 73 FR 21643 (April 22, 2008)
1.3.2 Listing history
Original Listing
FR notice: 64 FR 47126
Date listed: August 30, 1999
Entity listed: Lake Erie Water Snakes (Nerodia sipedon insularum) on the Offshore Islands of Western Lake Erie
Classification: Threatened
1.3.3 Associated rulemakings: None
1.3.4 Review History: None.
1.3.5 Species’ Recovery Priority Number at start of 5-year review: 9C,
indicating a moderate degree of threat, high recovery potential, and conflict with economic development for this subspecies.
1.3.6 Recovery Plan
Name of plan: Lake Erie Watersnake Recovery Plan (Nerodia sipedon
insularum)
Date issued: September 25, 2003
Dates of previous revisions, if applicable: None
2.0 REVIEW ANALYSIS
2.4 Synthesis
The Lake Erie Watersnake is a federally threatened, island-dwelling subspecies with a
very narrow range, encompassing the offshore islands of the western Lake Erie basin in
Ohio and Ontario.
Lake Erie Watersnake summer habitat is composed of rocky shorelines with limestone or
dolomite shelves, ledges, or boulders for sunning and shelter. Shelter occurs in the form
of loose rocks, piled rocks, or shelves and ledges with cracks, crevices, and nearby
vegetation. Rip-rap erosion control, armor stone, and docks incorporating a stone crib
structure often serve as summer habitat for the snake. Since the time of listing,
substantial research on Lake Erie Watersnake habitat use and foraging behavior has been
completed. Lake Erie Watersnakes typically forage for fish and amphibians in Lake Erie,
and recent research indicates that more than ninety percent of their current diet is
composed of the nonnative, invasive fish round goby (King et al. 2006). Jones et al.
(2009) report that the mean foraging distance from shore was 85 m (279 ft), and the
average water depth of the foraging locations was 3.32 m (10.9 ft). During the summer,
75 percent of Lake Erie Watersnakes are found within 13 m (42.7 ft) of the water’s edge
(King 2003). King (2003) identified that 75 percent of Lake Erie Watersnakes used 437
m (1433 ft) of shoreline or less as a home range. In the winter, Lake Erie Watersnakes
hibernate below the frost level, in cracks or crevices in the bedrock, interstitial spaces of
rocky substrates, tree roots, building foundations, and other similar natural and humanmade
structures. Seventy-five percent of Lake Erie Watersnakes hibernate within 69 m
(226 ft) of the water’s edge (King 2003). Individual snakes often demonstrate site
fidelity, returning to the same shoreline area and the same or nearby hibernacula in
successive years (King 2003).
The Lake Erie Watersnake Recovery Plan (USFWS 2003) remains current and addresses
appropriately all the known threats to the subspecies. Since the time of listing, nine years
of focused effort by State and Federal wildlife agencies, Universities, and nongovernment
partners has resulted in significant population and habitat protection and
improvements for Lake Erie Watersnake. Intensive annual census activities and markrecapture
population estimates indicate that Lake Erie Watersnake populations have
grown steadily since the time of listing and have far exceeded the recovery criterion of
5,555 adult animals, with a 2008 population estimate of 8,600 adult Lake Erie
Watersnakes (King and Stanford 2009). Further, King and Stanford (2009) documented
realized population growth of approximately 6 percent per year for the years 2001-2008,
with 95 percent confidence limits of 2-10 percent, providing strong evidence of
population growth across multiple sites.
Additionally, land protection and management efforts by ODNR and other partners have
resulted in the protection of 11.27 miles of shoreline habitat and 313.88 acres of suitable
habitat within 69m of the shoreline across the U.S. Lake Erie islands being permanently
protected and managed to benefit Lake Erie Watersnake, exceeding the recovery criterion
(USFWS 2003). Finally, extensive outreach efforts are reaching the desired audiences,
and most island residents are aware of the snake and its protected status (Wilkinson
2008). While public perception of and attitudes toward the snake are mixed, several
public opinion surveys (Olive 2008, Wilkinson 2008) indicated that the vast majority of
island residents would not resort to killing snakes they encountered on their property,
even if the snake was no longer listed.
A few additional notable changes in the species status since listing and issuance of the
recovery plan warrant discussion here.
Range Expansion
Since the time of listing, Lake Erie Watersnakes have naturally recolonized Green
Island, a small island close to South Bass Island, and a viable population of adult
watersnakes has persisted there for six years after an absence of 10 or more years
(King and Stanford 2009; King 2002). This natural recolonization demonstrates the
importance of maintaining multiple subpopulations of the Lake Erie Watersnake on
as many islands as possible, to provide source populations for recolonization, should
a stochastic event occur that eliminates all or a significant portion of the population
on another island.
Lake Erie Watersnakes are known from West Sister Island based on specimens
collected there in 1938 and 1939 but were not collected during repeated searches in
the 1980s and 1990s (King et al. 2006a). While it is not known why Lake Erie
Watersnakes disappeared from West Sister Island, it is the most isolated of the U.S. islands, located approximately 13.7 km (8.5 mi) from the mainland and
approximately 20.9 km (13.0 mi) from the nearest island. Three intensive snake
surveys since the time of listing have documented two adult female watersnakes on
West Sister Island, one in 2002 and one in 2008, though it is unclear if these
individuals were members of a permanent resident population, or transient individuals
that swam or drifted to the island (King and Stanford 2009). King and Stanford
(2009) indicate that “Lake Erie Watersnakes remain exceedingly rare or absent from
West Sister Island.”
Resilience of Lake Erie Watersnakes to Habitat Modification
The Lake Erie Watersnake has demonstrated resilience and behavioral plasticity to
both ecological and human-induced changes in its environment in the recent past. As
described above, the Lake Erie Watersnake has made a nearly complete dietary shift
since the invasion of the round goby in the early 2000’s indicating flexibility in prey
selection (King et al. 2006b). We have learned that crib docks and armored
shorelines provide valuable Lake Erie Watersnake summer habitat and that the Lake
Erie Watersnake can persist in stable numbers in human-dominated island landscapes,
so long as rocky or vegetated shorelines are present. Further, we have documented
multiple situations where Lake Erie Watersnakes have been able to identify and
successfully use new hibernation sites when historical hibernation sites are destroyed
or unavailable, thus indicating that the Lake Erie Watersnake is more resilient to
hibernation habitat modification than was previously known. The Lake Erie
Watersnake has also demonstrated its ability to naturally re-colonize historic habitat
after an absence of many years. Thus, despite any remaining threats, we believe the
Lake Erie Watersnake has sufficient resiliency to persist within the foreseeable future.
Climate Change
Global climate change due to trapping of greenhouse gases, particularly carbon
dioxide, within the atmosphere is widely predicted by scientists all over the world
(IPCC 2007). Within the Great Lakes region and Ohio specifically, climate change is
expected to bring increased temperatures, increased but altered distribution patterns
of precipitation, and greater intensity of extreme weather events including drought,
storms, floods, and heat waves (Karl et al. 2003; Kling et al. 2003). Winters will be
of shorter duration and warmer temperatures and snow melt will occur earlier (Kling
et al. 2003). These projected changes in seasonal temperature patterns may cause
Lake Erie Watersnakes to hibernate for shorter periods of time, to seek cover more
frequently during the active season to escape extreme weather events, and to forage
more frequently than they do now to compensate for an extended active season. It is
unlikely that these potential behavioral changes brought on by warmer temperatures
would constitute a threat to the population.
Warmer temperatures and decreased ice cover across the Great Lakes region
predicted by multiple models could result in warmer water temperatures and water
levels between 0.3-0.6 m (1-2 ft) below current levels in Lake Erie (Karl et al. 2009;
Kling et al. 2003). Decreases in Lake Erie water levels, which define the boundaries
of the western Lake Erie islands, can lead to increases in the area of the island
exposed, expansion or loss of coastal wetland habitat (depending on elevation and
topography), changes in extent and/or composition of island shoreline habitat, and
changes in erosion and accretion patterns. Over all, lower water levels will likely
create additional linear footage of island shorelines within the western Lake Erie basin, potentially expanding Lake Erie Watersnake summer terrestrial habitat areas.
Portions of former foraging habitat may become dry, requiring watersnakes to seek
out additional foraging territories. Water depth decreases of 0.3-0.6 m (1-2 ft) are
unlikely to disturb large portions of Lake Erie Watersnake foraging habitat. As noted
previously, Lake Erie Watersnakes’ diets are composed primarily of round goby,
which are plentiful in the warm waters of the western Lake Erie island region, and
would likely remain plentiful despite potential effects from climate change. It is
unlikely that lower water levels would significantly change Lake Erie Watersnake
behavior, or represent a threat to the population.
Climate change projections for Lake Erie indicate that increases in water temperature
during the summer may result in lower dissolved oxygen, and prolonged stratification
of lake water, resulting in an increase in the potential for dead-zones to occur or
expand across time and space (Karl et al. 2009; Kling et al. 2003). However, the
western Lake Erie basin is generally shallow, with an average depth of 7.4 m (24 ft),
and stratification is rare here, and brief when it does occur (USEPA and Environment
Canada 2008), and therefore we do not anticipate a threat to the population from this
projected change. However, low dissolved oxygen could also result in more easily
mobilized mercury and other contaminants that exist in Lake Erie sediments, and
introduction of increased contaminant loads into the food chain (Karl et al. 2009). As
discussed above, contaminants have been detected in Lake Erie Watersnakes in
relatively high levels, but have not been documented to cause adverse effects. It is
possible that additional contaminant loads could result in physiological or
reproductive impacts to Lake Erie Watersnakes, but at what level this contamination would have to be is unknown.
Warmer lake waters are anticipated to result in coldwater habitat being eliminated or
shifting north in some areas, potentially changing the fish communities in these areas
(Karl et al. 2009; Kling et al. 2003). However, the western basin of Lake Erie is
composed of warmwater habitat already (USEPA and Environment Canada 2008) and
is too shallow to support coldwater habitat, therefore we do not anticipate shifts in
fish species composition within the western Lake Erie basin due to climate change,
and therefore no threat to the Lake Erie Watersnake is anticipated.
At this time, we do not have sufficient information to document that climate change
poses a significant threat to the continued existence of the Lake Erie Watersnake.
Canadian status
The range of the Lake Erie Watersnake includes all islands in the western Lake Erie
basin, including islands in Ohio and Canada. Lake Erie Watersnakes are listed as an
endangered species in Canada, and are afforded legal protection. While some limited
amount of intra-island movement by Lake Erie Watersnakes has been documented,
most Lake Erie Watersnakes demonstrate site fidelity, returning to the same or nearby
summer shoreline areas and winter hibernation sites each year. King (1987) estimates
that less than 3% of Lake Erie Watersnakes move among islands or among sites on a
given island each year. Therefore, Lake Erie Watersnakes that occur on the U.S.
islands are unlikely to be threatened by activities, events, or individuals occurring on
the Canadian islands.
Previously recognized threats of habitat destruction, little or no legal protection, and
human persecution no longer affect the existence of the watersnake. Current available
information shows that the populations are persisting and a substantial amount of habitat
is now secured and managed. Recovery of Lake Erie Watersnake has been achieved
(USFWS 2003). Based on this 5-year review, Lake Erie Watersnake does not meet the
definition of an endangered or threatened species, and therefore delisting the species due
to recovery is recommended.
3.0 RESULTS
3.1 Recommended Classification:
____ Downlist to Threatened
____ Uplist to Endangered
__X_ Delist (Indicate reasons for delisting per 50 CFR 424.11):
____ Extinction
__X_ Recovery
____ Original data for classification in error
____ No change is needed
3.2 New Recovery Priority Number: 15.
Brief Rationale: Recovery criteria met; threats removed, abundant habitat
secured, protected and managed; populations persisting.
3.3 Listing and Reclassification Priority Number
Delisting Priority Number: 2
Brief Rationale: The Delisting Priority Number is “2,” indicating that the
management impact from delisting this subspecies is high, and that this is not a
petitioned action. The Service currently spends a significant amount of staff time
and resources consulting on Section 7 activities that may affect the Lake Erie
Watersnake, and implementing ongoing recovery actions for the snake. As the
Lake Erie Watersnake is currently meeting all the recovery criteria, we believe
these resources could be directed to species more deserving of conservation
efforts. Delisting is not a petitioned action, however it should be noted that in a
recent settlement agreement regarding critical habitat for Lake Erie Watersnake,
the Service agreed that if we did not propose delisting the Lake Erie Watersnake
during fiscal year 2009, we would reevaluate the need to designate critical habitat
for this subspecies. The process for designating critical habitat would create a
large management burden for a subspecies that may not warrant such effort due to
recovery.
4.0 RECOMMENDATIONS FOR FUTURE ACTIONS
All of the Recovery Criteria in the Lake Erie Watersnake Recovery Plan (USFWS 2003)
have been met, and the majority of the recovery actions in the Plan have also been
completed. At this time, Lake Erie Watersnake shows substantial recovery, and we
recommend initiation of the delisting process during Fiscal Year 2009, which will include
development of a proposed rule and post-delisting monitoring plan.
Above are the General Information, Synthesis, and Results portions of the Five-Year Review. Go here for the complete 23-page Review (PDF).
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