Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the North American Wolverine as Endangered or Threatened, 78030-78061 [2010-30573]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 239 (Tuesday, December 14, 2010)]
[Proposed Rules]
[Pages 78030-78061]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-30573]



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Part III





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; 12-Month Finding on a 
Petition To List the North American Wolverine as Endangered or 
Threatened; Proposed Rule

Federal Register / Vol. 75 , No. 239 / Tuesday, December 14, 2010 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R6-ES-2008-0029; MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List the North American Wolverine as Endangered or 
Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the North American wolverine 
(Gulo gulo luscus) as an endangered or threatened species under the 
Endangered Species Act of 1973, as amended (Act). After review of all 
available scientific and commercial information, we find that the North 
American wolverine occurring in the contiguous United States is a 
distinct population segment (DPS) and that addition of this DPS to the 
Lists of Endangered and Threatened Wildlife and Plants is warranted. 
Currently, however, listing the contiguous U.S. DPS of the North 
American wolverine is precluded by higher priority actions to amend the 
Lists of Endangered and Threatened Wildlife and Plants. Upon 
publication of this 12-month petition finding, we will add the 
contiguous U.S. DPS of the wolverine to our candidate species list. We 
consider the current range of the species to include portions of the 
States of Washington, Idaho, Montana, Wyoming, Colorado, Utah, Oregon, 
and California. However, due to the dispersal abilities of individual 
wolverines, we expect that wolverines are likely to travel outside the 
currently occupied area. We will develop a proposed rule to list this 
DPS as our priorities allow (see section on Preclusion and Expeditious 
Progress). We will make any determination on critical habitat during 
development of the proposed listing rule. In the interim, we will 
address the status of this DPS through our annual Candidate Notice of 
Review.

DATES: This finding was made on December 14, 2010.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R6-ES-2008-0029. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, Montana Field Office, U.S. Fish and Wildlife 
Service, 585 Shepard Way, Helena, MT 59601; telephone (406) 449-5225. 
Please submit any new information, materials, comments, or questions 
concerning this finding to the above address.

FOR FURTHER INFORMATION CONTACT: Mark Wilson, Field Supervisor, U.S. 
Fish and Wildlife Service, Montana Field Office (see ADDRESSES); by 
telephone at 406-449-5225; or by facsimile at 406-449-5339. If you use 
a telecommunications device for the deaf (TDD), call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.) requires 
that, for any petition to revise the Federal Lists of Endangered and 
Threatened Wildlife and Plants that contains substantial scientific and 
commercial information that listing a species may be warranted, we make 
a finding within 12 months of the date of receipt of the petition. In 
this finding, we determine whether the petitioned action is: (a) Not 
warranted, (b) warranted, or (c) warranted, but the immediate proposal 
of a regulation implementing the petitioned action is precluded by 
other pending proposals to determine whether species are threatened or 
endangered, and whether expeditious progress is being made to add or 
remove qualified species from the Federal Lists of Endangered and 
Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires 
that we treat a petition for which the requested action is found to be 
warranted but precluded as though resubmitted on the date of such 
finding, that is, requiring a subsequent finding to be made within 12 
months. We must publish these 12-month findings in the Federal 
Register.

Previous Federal Actions

    On April 19, 1995, we published a finding (60 FR 19567) that a 
previous petition, submitted by the Predator Project (now named the 
Predator Conservation Alliance) and Biodiversity Legal Foundation to 
list the wolverine in the contiguous United States, did not provide 
substantial information indicating that listing the wolverine in the 
contiguous United States may be warranted.
    On July 14, 2000, we received a petition dated July 11, 2000, 
submitted by the Biodiversity Legal Foundation, Predator Conservation 
Alliance, Defenders of Wildlife, Northwest Ecosystem Alliance, Friends 
of the Clearwater, and Superior Wilderness Action Network, to list the 
wolverine within the contiguous United States as a threatened or 
endangered species and designate critical habitat for the species.
    On October 21, 2003, we published a 90-day finding that a petition 
to list the wolverine in the contiguous United States failed to present 
substantial scientific and commercial information indicating that 
listing may be warranted (68 FR 60112).
    On September 29, 2006, as a result of a complaint filed by 
Defenders of Wildlife and others alleging we used the wrong standards 
to assess the wolverine petition, the U.S. District Court, Montana 
District, ruled that our 90-day petition finding was in error and 
ordered us to make a 12-month finding for the wolverine. On April 6, 
2007, a deadline for this 12-month finding was extended to February 28, 
2008.
    On March 11, 2008, we published a 12-month finding of ``not 
warranted'' for the wolverine in the contiguous United States (73 FR 
12929). In that finding we determined that the wolverine in the 
contiguous United States did not constitute a distinct population 
segment or a significant portion of the range of wolverines in North 
America and so was not eligible for listing under the Act.
    On July 8, 2008 we received a Notice of Intent to Sue from 
Earthjustice alleging violations of the Act in our March 11, 2008, 12-
month finding. On September 30, 2008, Earthjustice filed a complaint in 
the U.S. District Court, District of Montana, seeking to set aside and 
remand the 12-month finding back to the Service for reconsideration.
    On March 6, 2009, the Service agreed to settle the case with 
Earthjustice by voluntarily remanding the 12-month finding and issuing 
a new 12-month finding by December 1, 2010. Following the settlement 
agreement, the court dismissed the case on June 15, 2009, and ordered 
the Service to comply with the settlement agreement.
    On April 15, 2010, the Service published a Notice of Initiation of 
a 12-month finding for wolverines in the contiguous United States (75 
FR 19591).

Species Information

Taxonomy and Life History
    The wolverine has a holarctic distribution including northern 
portions of Europe, Asia, and North America. The currently accepted 
taxonomy classifies wolverines worldwide as a single species, Gulo 
gulo. Old and New World wolverines are divided into separate 
subspecies. Wolverines in the

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contiguous United States are a part of the New World subspecies, G. g. 
luscus: the North American wolverine (Kurten and Rausch 1959 p. 19; 
Pasitschniak-Arts and Lariviere 1995, p. 1). The species is known by 
several common names including mountain devil, glutton, caracajou, 
quickhatch, gulon, skunk bear, as well as wolverine.
    The wolverine is the largest terrestrial member of the family 
Mustelidae. Adult males weigh 12 to 18 kilograms (kg) (26 to 40 pounds 
(lb), and adult females weigh 8 to 12 kg (17 to 26 lb) (Banci 1994, p. 
99). The wolverine resembles a small bear with a bushy tail. It has a 
broad, rounded head; short, rounded ears, and small eyes. Each foot has 
five toes with curved, semi-retractile claws used for digging and 
climbing (Banci 1994, p. 99).
    A large number of female wolverines (40 percent) are capable of 
giving birth at 2 years old, become pregnant most years, and produce 
litter sizes of approximately 3.4 kits on average. Pregnant females 
commonly resorb or spontaneously abort litters prior to giving birth 
(Magoun 1985, pp. 30-31; Copeland 1996, p. 43; Persson et al. 2006, p. 
77; Inman et al. 2007c, p. 70). It is likely that, despite the high 
rate of initiation of pregnancy, due to the spontaneous abortion of 
litters resulting from resource limitation, actual rates of successful 
reproduction in wolverines are among the lowest known for mammals 
(Persson 2005, p. 1456). In one study of known-aged females, none 
reproduced at age 2, 3 of 10 first reproduced at age 3, and 2 did not 
reproduce until age 4; the average age at first reproduction was 3.4 
years (Persson et al. 2006, pp. 76-77). The average age at first 
reproduction is likely more than 3 years (Inman et al. 2007c, p. 70).
    It is common for females to forgo reproducing every year, possibly 
saving resources to increase reproductive success in subsequent years 
(Persson 2005, p. 1456). Supplemental feeding of females increases 
reproductive potential (Persson 2005, p. 1456). Food-supplemented 
females were also more successful at raising kits to the time of 
weaning, suggesting that wolverine reproduction and ultimately 
population growth rates and viability are food-limited. By age 3, 
nearly all female wolverines become pregnant every year, but energetic 
constraints due to low food availability result in loss of pregnancy in 
about half of them each year. It is likely that, in many places in the 
range of wolverines, it takes 2 years of foraging for a female to store 
enough energy to successfully reproduce (Persson 2005, p. 1456).
    Breeding generally occurs from late spring to early fall (Magoun 
and Valkenburg 1983, p. 175; Mead et al. 1991, pp. 808-811). Females 
undergo delayed implantation until the following winter to spring, when 
active gestation lasts from 30 to 40 days (Rausch and Pearson 1972, pp. 
254-257). Litters are born from mid-February through March, containing 
one to five kits, with an average in North America of between 1 and 2 
kits (Magoun 1985, pp. 28-31; Copeland 1996, p. 36; Krebs and Lewis 
1999, p. 698; Copeland and Yates 2006, pp. 32-36; Inman et al. 2007c, 
p. 68).
    Female wolverines use natal (birthing) dens that are excavated in 
snow. Persistent, stable snow greater than 1.5 meters (m) (5 feet (ft)) 
deep appears to be a requirement for natal denning, because it provides 
security for offspring and buffers cold winter temperatures (Pulliainen 
1968, p. 342; Copeland 1996, pp. 92-97; Magoun and Copeland 1998, pp. 
1317-1318; Banci 1994, pp. 109-110; Inman et al. 2007c, pp. 71-72; 
Copeland et al. 2010, pp. 240-242). Female wolverines go to great 
lengths to find secure den sites, suggesting that predation is a 
concern (Banci 1994, p. 107). Natal dens consist of tunnels that 
contain well-used runways and bed sites and may naturally incorporate 
shrubs, rocks, and downed logs as part of their structure (Magoun and 
Copeland 1998, pp. 1315-1316; Inman et al. 2007c, pp. 71-72). In Idaho, 
natal den sites occur above 2,500 m (8,200 ft) on rocky sites, such as 
north-facing boulder talus or subalpine cirques in forest openings 
(Magoun and Copeland 1994, pp. 1315-1316). In Montana, natal dens occur 
above 2,400 m (7,874 ft) and are located on north aspects in avalanche 
debris, typically in alpine habitats near timberline (Inman et al. 
2007c, pp. 71-72). Offspring are born from mid-February through March, 
and the dens are typically used through late April or early May 
(Myrberget 1968, p. 115; Magoun and Copeland 1998, pp. 1314-1317; Inman 
et al. 2007b, pp. 55-59). Occupation of natal dens is variable, ranging 
from approximately 9 to 65 days (Magoun and Copeland 1998, pp. 1316-
1317).
    Females may move kits to multiple secondary (maternal) dens as they 
grow during the month of May (Pulliainen 1968, p. 343; Myrberget 1968, 
p. 115), although use of maternal dens may be minimal (Inman et al. 
2007c, p. 69). Timing of den abandonment is related to accumulation of 
water in dens (due to snow melt), the maturation of offspring, 
disturbance, and geographic location (Myrberget 1968, p. 115; Magoun 
1985, p. 73). After using natal and maternal dens, wolverines may also 
use rendezvous sites through early July. These sites are characterized 
by natural (unexcavated) cavities formed by large boulders, downed logs 
(avalanche debris), and snow (Inman et al. 2007c, p. 55-56).
Habitat, Space, and Food
    In North America, wolverines occur within a wide variety of alpine, 
boreal, and arctic habitats, including boreal forests, tundra, and 
western mountains throughout Alaska and Canada. The southern portion of 
the species' range extends into the contiguous United States, including 
high-elevation alpine portions of Washington, Idaho, Montana, Wyoming, 
California, and Colorado (Wilson 1982, p. 644; Hash 1987, p. 576; Banci 
1994, p. 102, Pasitschniak-Arts and Lariviere 1995, p. 499; Aubry et 
al. 2007, p. 2152; Moriarty et al. 2009, entire; Inman et al. 2009, pp. 
22-25). Wolverines do not appear to specialize on specific vegetation 
or geological habitat aspects, but instead select areas that are cold 
and receive enough winter precipitation to reliably maintain deep 
persistent snow late into the warm season (Copeland et al. 2010, 
entire). The requirement of cold, snowy conditions means that, in the 
southern portion of the species' range where ambient temperatures are 
warmest, wolverine distribution is restricted to high elevations, while 
at more northerly latitudes, wolverines are present at lower elevations 
and even at sea level in the far north (Copeland et al. 2010, Figure 
1).
    In the contiguous United States, wolverines likely exist as a 
metapopulation (Aubry et al. 2007, p. 2147, Figures 1, 3). A 
metapopulation is a network of semi-isolated populations, each 
occupying a suitable patch of habitat in a landscape of otherwise 
unsuitable habitat (Pulliam and Dunning 1997, pp. 212-214). 
Metapopulations require some level of regular or intermittent migration 
and gene flow among subpopulations, in which individual populations 
support one-another by providing genetic and demographic enrichment 
through mutual exchange of individuals (Meffe and Carroll 1997, p. 
678). Individual subpopulations may go extinct or lose genetic 
viability, but are then ``rescued'' by immigration from other 
subpopulations, thus ensuring the persistence of the metapopulation as 
a whole. Metapopulation dynamics (the process of extinction and 
recolonization by subpopulations) rely on the ability of subpopulations 
to support one another through exchange of individuals for genetic and 
demographic enrichment. If

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metapopulation dynamics break down, either due to changes within 
subpopulations or loss of connectivity, then the entire metapopulation 
may be jeopardized due to subpopulations becoming unable to persist in 
the face of inbreeding or demographic and environmental stochasticity 
(Pulliam and Dunning 1997b, pp. 221-222). We believe this outcome is 
likely for wolverine, due to their naturally low reproductive rates and 
low densities.
    Wolverines are opportunistic feeders and consume a variety of foods 
depending on availability. They primarily scavenge carrion, but also 
prey on small animals and birds, and eat fruits, berries, and insects 
(Hornocker and Hash 1981, p. 1290; Hash 1987, p. 579; Banci 1994, pp. 
111-113). Wolverines have an excellent sense of smell that enables them 
to find food beneath deep snow (Hornocker and Hash 1981, p. 1297).
    Wolverines require a lot of space; the availability and 
distribution of food is likely the primary factor in determining 
wolverine movements and home range size (Hornocker and Hash 1981, p. 
1298; Banci 1994, pp. 117-118). Female wolverines forage close to den 
sites in early summer, progressively ranging further from dens as kits 
become more independent (May et al. 2010, p. 941). Wolverines travel 
long distances over rough terrain and deep snow, and adult males 
generally cover greater distances 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). Home ranges of wolverines are large, and vary greatly 
in size depending on availability of food, gender and age of the 
animal, and differences in habitat quality. Home ranges of adult 
wolverines also vary in size depending on geographic location. Home 
ranges in Alaska were approximately 100 square kilometers (km\2\) to 
over 900 km\2\ (38.5 square miles (mi\2\) to 348 mi\2\) (Banci 1994, p. 
117). Average home ranges of resident adult females in central Idaho 
were 384 km\2\ (148 mi\2\), and average home ranges of resident adult 
males were 1,522 km\2\ (588 mi\2\) (Copeland 1996, p. 50). Wolverines 
in Glacier National Park had average adult male home ranges of 496 
km\2\ (193 mi\2\) and adult female home ranges of 141 km\2\ (55 mi\2\) 
(Copeland and Yates 2006, p. 25). Wolverines in the Greater Yellowstone 
Ecosystem had average adult male home ranges of 797 km\2\ (311 mi\2\), 
and average adult female home ranges of 329 km\2\ (128 mi\2\) (Inman et 
al. 2007a, p. 4). These home range sizes are large relative to the body 
size of wolverines, and may indicate that wolverines occupy a 
relatively unproductive niche in which they must forage over large 
areas to consume the amount of calories needed to meet their life-
history requirements (Inman et al. 2007a, p. 11).
Wolverine Densities
    Wolverines naturally occur in low densities of about 1 wolverine 
per 150 km\2\ (58 mi\2\) with a reported range from 1 per 65 to 337 
km\2\ (25 to 130 mi\2\) (Hornocker and Hash 1981, pp. 1292-1295; Hash 
1987, p. 578; Copeland 1996, pp. 31-32; Copeland and Yates 2006, p. 27; 
Inman et al. 2007a, p. 10; Squires et al. 2007, p. 2218). No systematic 
population census exists over the entire current range of wolverines in 
the contiguous United States, so the current population level and 
trends remain unknown. However, based on our current knowledge of 
occupied wolverine habitat and wolverine densities in this habitat, it 
is reasonable to estimate that the wolverine population in the 
contiguous United States numbers approximately 250 to 300 individuals 
(Inman 2010b, pers. comm.). The bulk of the current population occurs 
in the northern Rocky Mountains with a few individuals in the North 
Cascades and one known individual each in the Sierra Nevada and 
southern Rocky Mountains. Within the area known to currently have 
wolverine populations relatively few wolverines can coexist due to 
their naturally low population densities, even if all areas were 
occupied at or near carrying capacity. Given the natural limitations on 
wolverine population density, it is likely that historic wolverine 
population numbers were also low (Inman et al. 2007a, Table 6). Because 
of these natural limitations, we believe that densities and population 
levels in the northern Rocky Mountains and North Cascades where 
populations currently exist are likely not substantially lower than 
population densities were in these areas prior to European settlement. 
However, historically, the contiguous U.S. population would have been 
larger than it is today due to the larger area occupied by populations 
when the southern Rocky Mountains and Sierra Nevada were occupied at 
full capacity.
Wolverine Status in Canada and Alaska
    The bulk of the range of North American wolverines is found in 
Canada and Alaska. Wolverines inhabit alpine tundra, boreal forest, and 
arctic habitats in Canada and Alaska (Slough 2007, p. 78). Wolverines 
in Canada have been divided into two populations for management by the 
Canadian Government: An eastern population in Labrador and Quebec, and 
a western population that extends from Ontario to the Pacific coast, 
and north to the Arctic Ocean. The eastern population is currently 
listed as endangered under the Species At Risk Act in Canada, and the 
western population is designated as a species of special concern 
(COSEWIC 2003, p. 8).
    The current status of wolverines in eastern Canada is uncertain. 
Wolverines have not been confirmed to occur in Quebec since 1978 
(Fortin et al. 2005, p. 4). Historical evidence of wolverine presence 
in eastern Canada is also suspect because no proof exists to show that 
wolverine pelts attributed to Quebec or Labrador actually came from 
that region; animals were possibly trapped elsewhere and the pelts 
shipped through the eastern provinces (COSEWIC 2003, p. 20). Wolverines 
in eastern Canada may currently exist in an extremely low-density 
population, or may be extirpated. Wolverines in eastern Canada, both 
historically and currently, could represent migrants from western 
populations that never became resident animals (COSEWIC 2003, pp. 20-
21). The Federal Government of Canada has completed a recovery plan for 
the eastern population with the goal of establishing a self-sustaining 
population through reintroduction and protection (Fortin et al. 2005, 
p. 16).
    Wolverines in western Canada and Alaska inhabit a variety of 
habitats from sea level to high in mountains (Slough 2007, pp. 77-78). 
They occur in Ontario, Manitoba, Saskatchewan, Alberta, British 
Columbia, Yukon, Northwest Territories, and Nunavut (Slough 2007, pp. 
77-78). Since European colonization, a generally recognized range 
contraction has taken place in boreal Ontario and the aspen parklands 
of Manitoba, Saskatchewan, and Alberta (COSEWIC 2003, pp. 20-21; Slough 
2007, p. 77). This range contraction occurred concurrently with a 
reduction in wolverine records for the Great Lakes region in the 
contiguous United States (Aubry et al. 2007, pp. 2155-2156). Causes of 
these changes are uncertain, but may be related to increased harvest, 
habitat modification, or climate change (COSEWIC 2003, pp. 20-21; Aubry 
et al. 2007, pp. 2155-2156; Slough 2007, pp. 77-78). Analysis supports 
climate change as a contributing factor to declines in southern 
Ontario, because snow conditions necessary to support wolverines do not 
currently exist in the Great Lakes region of the contiguous United 
States, and are marginal in southern Ontario (Aubry et al. 2007, p. 
2154). It is not known if these snow

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conditions existed historically in the Great Lakes of the contiguous 
United States, however, the small number of wolverine records from this 
area suggests that they did not. It is possible that suitable snow 
conditions did reach further south in eastern Canada in 1850 than they 
do today, making wolverine dispersal attempts from Canada to the Great 
Lakes region of the contiguous United States more likely than they are 
now. Wolverines occurred historically on Vancouver Island and have been 
given status as a separate subspecies by some (Hall 1981, p. 109). The 
Vancouver Island population is now regarded as possibly extirpated; no 
sightings have occurred since 1992 (COSEWIC 2003, p. 18).
    Wolverines in western Canada and Alaska appear to persist 
everywhere that habitat and climate conditions are suitable (COSEWIC 
2003, pp. 13-21; Aubry et al. 2007, pp. 2152-2155; Slough 2007, p. 79; 
Copeland et al. 2010, Figure 2). Throughout this area, wolverines are 
managed by regulated harvest at the Provincial and State level. 
Population estimates for Canada and Alaska are rough because no 
wolverine surveys have taken place at the State or Provincial scale. 
However, the population in western Canada is estimated to include 
approximately 15,089 to 18,967 individuals (COSEWIC 2003, p. 22). The 
number of wolverines in Alaska is unknown, but they appear to exist at 
naturally low densities in suitable habitats throughout Alaska (Alaska 
Department of Fish and Game 2004, pp. 1-359). We have no information to 
indicate that wolverine populations have been reduced in numbers or 
geographic range in Alaska.
The Complexity of Geographic Range Delineation
    Delineating wolverine historical and present range is inherently 
difficult for several reasons. Wolverines tend to live in remote and 
inhospitable places away from human populations where they are seldom 
encountered, documented, or studied. Wolverines naturally occur at low 
population densities and are rarely and unpredictably encountered where 
they do occur. Wolverines often move long distances in short periods of 
time, when dispersing from natal ranges, into habitats that are 
unsuitable for long-term survival (Aubry et al. 2007, p. 2147; Moriarty 
et al. 2009, entire; Inman et al. 2009, pp. 22-28; Brian 2010, p. 3). 
Such movements make it difficult to distinguish with certainty between 
occurrence records that represent established populations and those 
that represent short-term occupancy or exploratory movements without 
the potential for establishment of home ranges, reproduction, and 
eventually populations. These natural attributes of wolverines make it 
difficult to precisely determine their present range, or trends in 
range expansion or contraction that may have occurred in the past. 
Therefore, we must be cautious and use multiple lines of evidence when 
trying to determine where past wolverine populations occurred.
    Throughout the remainder of this finding, we focus on the use of 
verifiable and documented wolverine occurrence records to define 
historic and present range because we have determined that these 
records constitute the best scientific information available on the 
past and present distribution of wolverines (See Aubry et al. 2007, p. 
2148). Verifiable records are records supported by physical evidence 
such as museum specimens, harvested pelts, DNA samples, and diagnostic 
photographs. Documented records are those based on accounts of 
wolverines being killed or captured. Use of only verifiable and 
documented records avoids mistakes of misidentification often made in 
eyewitness accounts of visual encounters. Visual-encounter records 
often represent the majority of occurrence records for elusive forest 
carnivores, and their inherently high rate of misidentification of the 
species involved can result in wildly inaccurate conclusions about 
species occurrence (McKelvey et al. 2008, entire). The paper by Aubry 
et al. (2007, entire) utilized only verifiable and documented records 
to investigate wolverine distribution through time. This paper is the 
only available comprehensive treatment of these distribution patterns 
that attempts to distinguish between records that represent resident 
animals versus animals that have dispersed outside of suitable habitat. 
For these reasons we believe that Aubry et al. (2007, entire) 
represents the best available summary of wolverine occurrence records 
in the contiguous United States at this time. Since the publication of 
Aubry et al. (2007, entire), verified records of wolverine have also 
been documented in Colorado and California, which we will describe in 
greater detail below.
    Aubry et al. (2007, entire) used verifiable and documented records 
from museum collections, literature sources, and State and Federal 
institutions to trace changes in geographic distribution of wolverines 
in the historic record. They then used an overlay of suitable wolverine 
habitats to further refine which records represent wolverines in 
habitats that may support residency, and by extension, populations, and 
which records likely represent wolverines outside the range of suitable 
habitats, so called ``extralimital'' records. Aubry et al.'s (2007, 
entire) focus on verifiable and documented records corrected past 
overly broad approaches to wolverine range mapping (Nowak 1973, p. 22; 
Hall 1981, p. 1009; Wilson 1982, p. 644; Hash 1987, p. 576) that used a 
more inclusive but potentially misleading approach when dealing with 
occurrence records. Many of the extralimital records used in these 
publications represent individuals dispersing from natal ranges that 
ended up in habitats that cannot support wolverines, and the use of 
this data to determine the historic geographic range of wolverines 
results in gross overestimation of the area that can actually be used 
successfully by wolverines for the establishment of populations. 
Subsequent to publication of Aubry et al. (2007, entire), Copeland et 
al. (2010, entire) further refined our understanding of wolverine 
habitat needs and corroborated the approach of Aubry et al. (2007, 
entire).
    We agree with Aubry et al. (2007, p. 2149) that the most 
appropriate method to determine the current and historic range of 
wolverines is to use a combination of occurrence records and habitat 
suitability, along with other information, such as documented 
successful reproduction events, that indicate where reproductive and 
potentially self-sustaining populations may occur. We also generally 
agree with their conclusions about the historic and current range of 
the species. We believe that the species' range is the area that may 
support viable populations, and does not include extralimital 
occurrences outside of habitat that is likely to support wolverine 
life-history needs. Areas that can support wolverine populations may be 
referred to as potential ``source'' populations because they provide 
surplus individuals through reproduction beyond what is needed for 
replacement. Areas that do not have the habitat to support viable 
populations may be referred to as population ``sinks'' because 
wolverines may disperse to these areas and remain for some time, but 
will either die there without reproducing, leave the area in search of 
better habitat conditions, or may actually reproduce, but at a rate 
lower than that needed for replacement of individuals lost to mortality 
or emigration, leading to eventual population extinction. For a widely 
dispersing species like wolverines, we expect many locality records to 
represent dispersers into sink habitats. The value to the population 
(and thus

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the DPS) of these dispersers in sink habitat is unclear; however, it is 
likely that most dispersers into sink habitats will be lost to the 
population unless they are able to move back into source habitats. 
Therefore, it is our belief that population sink areas, here defined as 
places where wolverines may be found but where habitat is not suitable 
for long-term occupancy and reproduction, do not represent part of the 
species historic range and have little conservation value for the DPS, 
other than possibly serving as way-stations for attempted dispersers as 
they search for suitable habitats. This approach to defining historic 
range results in reducing the bias of extralimital dispersers and 
concentrates conservation attention on areas capable of maintaining 
populations, and is more in keeping with the intentions of the Act, 
than broader depictions of geographic range.
    Aubry et al. (2007, pp. 2147-2148) divided records into 
``historical'' (recorded prior to 1961), ``recent'' (recorded between 
1961 and 1994), and ``current'' (recorded after 1994). Historical 
records occurred before systematic surveys. Historical records 
encompass the time during which wolverine numbers and distribution were 
hypothesized to be at their highest (prior to European settlement) and 
also at their lowest (early 20th Century) (Wright and Thompson 1935; 
Grinnell et al. 1937; Allen 1942; Newby and Wright 1955, all as cited 
in Aubry et al. 2007, p. 2148). The recent time interval covers a 
hypothesized population expansion and rebound from the early 20th 
Century low. Current records offer the most recent evidence available 
for wolverine occurrences and potential populations. We believe all 
occurrence records must be individually analyzed in light of their 
context in terms of habitat conditions conducive to wolverine 
population establishment and whether or not they occur clustered with 
other records, which might indicate that populations have historically 
occurred in the area. The authors of Aubry et al. (2007) did such an 
analysis as they compiled their records.

Wolverine Distribution

    Of 729 mappable records (those records with precise location 
information) compiled by Aubry et al. (2007, p. 2150), 188 were from 
the historical time interval (see Figure 1). We assessed the 
historical, recent, and current distribution data for each of the 
regions below to determine the likelihood of the presence of historical 
populations (rather than extralimital dispersers). The discussion below 
draws heavily from both Aubry et al. (2007, entire) and Copeland et al. 
(2010, entire).

                   Table 1--Wolverine Records From Three Time Periods From Aubry et al. 2007.
[Numbers Represent Total Documented and Verifiable Records With the Subset of Those Records That Were Verifiable
                                                 in Parentheses]
----------------------------------------------------------------------------------------------------------------
                                                                  Historical  (<  Recent  (1961-    Current  (>
                                                                       1964)           1994)           1994)
----------------------------------------------------------------------------------------------------------------
Northeast.......................................................          13 (1)               0               0
Upper Midwest...................................................           4 (2)               0               0
Great Lakes.....................................................          36 (4)               1               0
Central Great Plains............................................        71 * (2)               1               0
Rocky Mountains.................................................        147 (45)       332 (283)       215 (210)
Pacific Coast...................................................         89 (14)         23 (15)               7
                                                                 -----------------------------------------------
    Totals......................................................        362 (68)       357 (298)       222 (210)
----------------------------------------------------------------------------------------------------------------
* 35 records from a single source (the journals of Alexander Henry).

    Northeast and Upper Midwest--The low number of records and 
scattered nature of their distribution combined with a lack of suitable 
habitat indicate that wolverines were likely only occasional transients 
to the area and not present as a reproducing population after 1800.
    Great Lakes--The lack of large numbers of verifiable records in 
this area of relatively high human population density and the lack of 
suitable habitat suggests that wolverines did not exist in this area as 
a viable population after 1900. Widely scattered records generally 
before 1900, with an occasional record after that year, suggest that if 
a reproducing population existed in the Great Lakes, it predated 1900, 
and that post-1900 records represent dispersal from a receding Canadian 
population. Wolverine distribution in Ontario, Canada, appears to have 
receded north from the Great Lakes region since the 1800s, and 
currently wolverines occupy only the northern portion of the province, 
a distance of over 400 miles from the U.S. border (COSEWIC 2003, p. 9). 
The pattern of record distribution illustrated in Aubry et al. (2007, 
p. 2152) is consistent with what would be expected if those records 
were of dispersing individuals from a Canadian population that receded 
progressively further north into Canada after 1900, possibly due to 
natural climate changes.
    Central Great Plains--The lack of precise locality records and 
suitable habitat from the Great Plains States leads us to conclude that 
reproducing populations of wolverines did not historically inhabit this 
area. Thirty-five of thirty-six records from North Dakota are from the 
journals of a single fur trader (see Table 1), and it is not clear that 
the records represent actual collection localities or are localities 
where trades or shipments occurred (Aubry 2007, pers. comm.). Given the 
habitat relationships of wolverines (e.g., Copeland et al. 2010, Figure 
1), it is unlikely that these records represent established wolverines 
or that this area was in any way wolverine habitat.
    Rocky Mountains--Five Rocky Mountains States (Idaho, Montana, 
Wyoming, Colorado, and Utah) contained numerous wolverine records. 
Records with precise locality information appear to coalesce around 
several areas that may have been population centers, such as central 
Colorado, the greater Yellowstone region, and northern Idaho-
northwestern Montana. The large number of verifiable and documented 
records for this region, along with the suggestion of population 
centers or strongholds, suggests that wolverines existed in reproducing 
populations throughout much of the Rocky Mountains during the 
historical time interval. The lack of records for Colorado and Utah 
after 1921 suggests that the southern Rocky Mountain population of 
wolverines was extirpated in the early 1900s, concurrent with

[[Page 78035]]

widespread systematic predator control by government agencies and 
livestock interests. The northern Rocky Mountain population (north of 
Wyoming) was reduced to historic lows or possibly even extirpated 
during the early 1900s, and then increased dramatically in the second 
half of the 1900s (see Table 1) as predator control efforts subsided 
and trapping regulations became more restrictive (Aubry et al. 2007, p. 
2151). This increase likely indicates a population rebound from 
historic lows in this period.
    Wolverine records from 1995 to 2005 indicate that wolverine 
populations currently exist in the northern Rocky Mountains (see Table 
1). Legal trapping in Montana in the recent past removed an average of 
10.5 individuals from this population each year (Montana Department of 
Fish, Wildlife, and Parks 2007, p. 2), and harvest mortality has been 
reduced due to regulatory changes in 2008 (Montana Department of Fish, 
Wildlife and Parks 2008, p. 8). Populations in British Columbia and 
Alberta, Canada, are extant (COSEWIC 2003, pp. 18-19), and may have 
been a source of surplus wolverines to the contiguous U.S. population 
during population lows. Recently, a male wolverine moved on its own 
from the southern Greater Yellowstone Area of Wyoming into the southern 
Rocky Mountains of Colorado where it still persisted as of August 2010 
(Inman et al. 2009, pp. 22-26; Inman 2010, pers. comm.). This attempted 
dispersal event is the first verified wolverine occurrence in Colorado 
since 1919 and may represent a continuation of the wolverine expansion 
in the Rocky Mountains detailed above. It is possible that other 
wolverines have travelled to the southern Rocky Mountains and have 
remained undetected. There is no evidence that Colorado currently hosts 
a wolverine population or that female wolverines have made, or are 
likely to make, similar movements.
    Pacific Coast--Historically, wolverines occurred in two population 
centers in the North Cascades Range and the Sierra Nevada. These areas 
are separated by an area with no historic records (southern Oregon and 
northern California), indicating that the historical distribution of 
wolverines in this area is best represented by two disjunct populations 
rather than a continuous peninsular extension from Canada. This 
conclusion is supported by genetic data indicating that the Sierra 
Nevada and Cascades wolverines were separated for at least 2,000 years 
prior to extirpation of the Sierra Nevada population (Schwartz et al. 
2007, p. 2174).
    Only one Sierra Nevada record exists after 1930, indicating that 
this population was likely extirpated in the first half of the 1900s 
concurrent with widespread systematic predator control programs. In 
2008, a male wolverine was discovered in the Sierra Nevada Range of 
California, the first verified record from California since 1922 
(Moriarty et al. 2009, entire). Genetic testing revealed that this 
wolverine was not a descendant of the endemic Sierra Nevada wolverine 
population, but was likely derived from wolverines in the Rocky 
Mountains (Moriarty et al. 2009, p. 159). This attempted dispersal 
event may represent a continuation of the wolverine expansion in the 
contiguous United States as detailed above. Other wolverines may have 
traveled to the Sierra Nevada and remain undetected. There is no 
evidence that California currently hosts a wolverine population or that 
female wolverines have made or are likely to make similar dispersal 
movements.
    Wolverines were likely extirpated from the North Cascades in the 
early 20th century and then recently recolonized from Canada. 
Currently, a small population persists in this area (Aubrey et al. 
2009, entire). The Northern Cascades population may be connected with, 
and is possibly dependent on, the larger Canadian population for future 
expansion and long-term persistence.

Summary of Wolverine Distribution

    Historical wolverine records were found across the northern tier of 
the contiguous United States with convincing evidence of wolverine 
populations in the northern and southern Rocky Mountains, Sierra Nevada 
Mountains, and North Cascades Mountains (Aubry et al. 2007, p. 2152).
    Currently, wolverines appear to be distributed as functioning 
populations in two regions in the contiguous United States: The North 
Cascades in Washington, and the northern Rocky Mountains in Idaho, 
Montana, and Wyoming. Wolverines were likely extirpated, or nearly so, 
from the entire contiguous United States in the first half of the 20th 
Century (Aubry et al. 2007, Table 1). The available evidence suggests 
that, in the second half of the 20th Century and continuing into the 
present time, wolverine populations have expanded in the North Cascades 
and the northern Rocky Mountains, but that populations have not been 
reestablished in the Sierra Nevada Range or the southern Rocky 
Mountains. We conclude that the current range of the species in the 
contiguous United States includes the North Cascades Mountains, the 
northern Rocky Mountains, the southern Rocky Mountains, and the Sierra 
Nevada Mountains, but that reestablishment of populations in the 
southern Rocky Mountains and Sierra Nevada has not yet occurred.
    We also conclude that wolverines either did not exist as 
established populations, or were extirpated prior to settlement and the 
compilation of historical records, in the Great Lakes region, possibly 
due to climate changes that occurred through the 1800s and 1900s. The 
Great Lakes region lacks suitable wolverine habitat, and suitable 
habitat does not appear to exist in adjacent Canada (Copeland et al. 
2010, Figure 1). The widely scattered records from this region are 
consistent with dispersing individuals from a Canadian population that 
receded north early in the 1800s. We cannot rule out the possibility 
that wolverines existed as established populations prior to the onset 
of trapping in this area, but we have no reliable evidence that they 
did.
    No reliable evidence in the historical records indicates that 
wolverines were ever present as established populations in the Great 
Plains, Midwest, or Northeast.

Habitat Relationships and Wolverine Distribution

    Deep, persistent, and reliable spring snow cover (April 15 to May 
14) is the best overall predictor of wolverine occurrence in the 
contiguous United States (Aubry et al. 2007, pp. 2152-2156; Copeland et 
al. 2010, entire). Deep persistent snow correlates well with wolverine 
year-round habitat use across wolverine distribution in North America 
and Eurasia at both regional and local scales (Copeland et al. 2010, 
entire). It is uncertain why spring snow cover so accurately predicts 
wolverine habitat use; however, it is likely related to wolverines' 
need for deep snow during the denning period, and also wolverines' 
physiological requirement for year-round cold temperatures (Copeland et 
al. 2010, pp. 242-243). Snow cover during the denning period is 
essential for successful wolverine reproduction range-wide (Hatler 
1989, p. iv; Magoun and Copeland 1998, p. 1317; Inman et al. 2007c, pp. 
71-72; Persson 2007; Copeland et al. 2010, p. 244). Wolverine dens tend 
to be in areas of high structural diversity such as logs and boulders 
with deep snow (Magoun and Copeland 1998, p. 1317; Inman et al. 2007c, 
pp. 71-72; Persson 2007, entire). Reproductive females dig deep snow 
tunnels to reach the protective structure provided by logs and 
boulders. This behavior presumably protects the

[[Page 78036]]

vulnerable kits from predation by large carnivores, including other 
wolverines (Pulliainen 1968, p. 342; Zyryanov 1989, pp. 3-12), but may 
also have physiological benefits for kits by buffering them from 
extreme cold, wind, and desiccation (Pullianen 1968, p. 342, 
Bj[auml]rvall et al. 1978, p. 23). Wolverines live in low-temperature 
conditions and appear to select habitats in part to avoid high summer 
temperatures (Copeland et al. 2010, p. 242). Wolverine distribution is 
likely affected by climatic conditions at two different scales. 
Wolverines require deep persistent snow for denning, and this likely 
determines where wolverine populations can be found at the grossest 
range-wide scale (Copeland et al. 2010, p. 244). At smaller scales, 
wolverines likely select habitats to avoid high summer temperatures. 
These cool habitats also tend to retain snow late into spring, leading 
to wolverines' year-round association with areas of persistent spring 
snow (Copeland et al. 2010, p. 244).
    All of the areas in the contiguous United States for which good 
evidence of persistent wolverine populations (either present or 
historic) exists (i.e., North Cascades, Sierra Nevada, northern and 
southern Rocky Mountains) contain large and well-distributed areas of 
deep snow cover that persists through the wolverine denning period 
(Brock et al. 2007, pp. 36-53; Aubry et al. 2007, p. 2154; Copeland et 
al. 2010, Figure 1). The Great Plains, Great Lakes, Midwest, and 
Northeast lack the spring snow conditions and low summer temperatures 
thought to be required by wolverines for successful reproduction and 
year-round occupancy (Aubry et al. 2007, p. 2154; Copeland et al. 2010, 
Figure 1). The lack of persistent spring snow conditions in the Great 
Plains, Great Lakes, Midwest, and Northeast supports the exclusion of 
these areas from the current range of wolverines. Whether wolverines 
once existed as established populations in any of these regions is 
uncertain, but the current climate appears to preclude their presence 
as reproducing populations now, and the sparse historical record of 
wolverine presence in this area makes historic occupation of these 
areas by wolverine populations doubtful. It is our conclusion that the 
ecosystem that supports wolverines does not exist in these areas 
currently, and may never have existed in the past.
    Large areas of habitat with characteristics suitable for wolverines 
still occur in the southern Rocky Mountains and Sierra Nevada, despite 
the extirpation of wolverines from those areas (Aubry et al. 2007, p. 
2154, Brock et al. 2007, p. 26; Copeland et al. 2010, Figure 1). 
Wolverine extirpations in these areas were coincident with systematic 
predator eradication efforts in the early 1900s, which have been 
discontinued for many years. Each of these areas has received at least 
one and possibly more migrants from adjacent populations in the 
northern Rocky Mountains; however, there is no evidence that females 
have migrated to these areas or that populations of wolverines exist in 
them (Aubry et al. 2007, Table 1; Moriarty et al. 2009, entire; Inman 
et al. 2009, entire).
    We conclude that areas of wolverine historical occurrence can be 
placed in one of three categories: (1) Areas where wolverines are 
extant as reproducing and potentially self-sustaining populations 
(North Cascades, northern Rocky Mountains); (2) areas where wolverines 
historically existed as reproducing and potentially self-sustaining 
populations prior to human-induced extirpation, and where 
reestablishment of those populations is possible given current habitat 
condition and management (the Sierra Nevada Mountains in California and 
southern Rocky Mountains in Colorado, New Mexico, Wyoming, and Utah); 
and (3) areas where historical presence of wolverines in reproducing 
and potentially self-sustaining populations is doubtful, and where the 
current habitat conditions preclude the establishment of populations 
(Great Plains, Midwest, Great Lakes, and Northeast). We, therefore, 
consider the current range of wolverines to include suitable habitat in 
the North Cascades of Washington and possibly Oregon, the northern 
Rocky Mountains of Idaho, Wyoming, and Montana, the southern Rocky 
Mountains of Colorado, Utah, and Wyoming, and the Sierra Nevada of 
California. We here include the Sierra Nevada and southern Rocky 
Mountains in the current range of wolverines despite the probability 
that functional populations do not exist in these areas. They are 
included due to the known existence of one individual in each area and 
the possibility that more, as yet undetected, individuals inhabit these 
areas.

Distinct Population Segment

    Pursuant to the Act, we must consider for listing any species, 
subspecies, or, for vertebrates, any Distinct Population Segment (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 Act and Congressional guidance, the Service and the National 
Marine Fisheries Service published, on February 7, 1996, an interagency 
Policy Regarding the Recognition of Distinct Vertebrate Population 
Segments under the Act (61 FR 4722). This policy addresses the 
recognition of DPSs for potential listing actions. The policy allows 
for more refined application of the Act 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 Act. These are applied similarly for additions to the list of 
endangered and threatened species, reclassification, and removal from 
the list. They are: (1) Discreteness of the population segment in 
relation to the remainder of the taxon; (2) the biological or 
ecological significance of the population segment to the taxon to which 
it belongs; and (3) the population segment's conservation status in 
relation to the Act's standards for listing (i.e., whether the 
population segment is, when treated as if it were a species or 
subspecies, endangered or threatened). Discreteness refers to the 
degree of 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, we must consider whether the discrete 
segment is ``significant'' to the taxon to which it belongs by using 
the best available scientific and commercial information. If we 
determine that a population segment is both discrete and significant, 
we then evaluate it for endangered or threatened status based on the 
Act's standards. The DPS evaluation in this finding concerns the 
segment of the wolverine species occurring within the 48 States, 
including the northern and southern Rocky Mountain physiographic 
provinces, Sierra Nevada Range, and North Cascades Range.

Distinct Population Segment Analysis for Wolverine in the Contiguous 
United States

Analysis of Discreteness

    Under our DPS Policy, a population segment of a vertebrate species 
may be considered discrete if it satisfies either one of the following 
conditions: (1) 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 (2) it is 
delimited by international governmental boundaries within which

[[Page 78037]]

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 Act (inadequacy of 
existing regulatory mechanisms). The wolverine within the contiguous 
United States meets the second DPS discreteness condition because of 
differences in conservation status as delimited by the Canadian-U.S. 
international governmental boundary.
Discreteness Based on the International Border--Differences in 
Conservation Status
    We find that differences in conservation status of the wolverine 
between the United States and Canada are substantial and significant in 
light of section 4(a)(1)(D) of the Act. In the remaining current range 
in Canada-Alaska, wolverines exist in well-distributed, interconnected, 
large populations. Conversely, wolverine populations in the remaining 
U.S. range appear to be at numbers so low that their continued 
existence could be at risk, especially as considered in light of the 
five threat factors discussed below. These risks come from three main 
factors: (1) Small total population size; (2) effective population size 
below that needed to maintain genetic diversity and demographic 
stability; and (3) the fragmented nature of wolverine habitat in the 
contiguous United States that results in smaller, isolated ``sky 
island'' patches separated by unsuitable habitats. It is apparent that 
maintaining wolverines within their native range in the contiguous 
United States into the future is likely to require regulatory 
mechanisms that are not currently in place. These three factors are 
explained in more detail below.
    The total population sizes for Canada-Alaska and the contiguous 
United States differ by more than an order of magnitude. The contiguous 
U.S. population likely numbers approximately 250 to 300 individuals 
(Inman 2010b, pers. comm.). This contrasts with western Canada, where 
wolverine populations are estimated at 15,089 to 18,967 individuals 
(COSEWIC 2003, p. 22). Wolverine population size in Alaska is unknown; 
however, the average annual harvest exceeds 500 individuals and the 
population does not appear to be in decline (Alaska Department of Fish 
and Game 2004, entire), indicating that the population is likely to 
number over ten thousand individuals (calculated using demographic data 
in Lofroth and Ott 2007, pp. 2196-2198; assumes sustainable harvest). 
The difference in total population size coincides with the 
international boundary between the contiguous United States and Canada. 
Wolverine populations number 2,089-3,567 in British Columbia and 1,500-
2,000 in Alberta (COSEWIC 2003, p. 22), the two provinces immediately 
adjacent to the contiguous U.S. wolverine population. The difference in 
total population sizes is significant because critically small 
populations such as those in the contiguous United States face higher 
extinction risk than large ones such as the Canada-Alaska population. 
Therefore, the contiguous U.S. population is more vulnerable to 
extinction, and thus of poor conservation status, relative to the more 
secure Canada-Alaska population.
    Wolverines in Canada's eastern provinces are listed under the 
Species at Risk Act of Canada. Wolverines in the eastern provinces 
appear to have been extirpated by the early 20th century (COSEWIC 2003, 
p. 20). There is a general lack of reliable historic information on 
wolverines in this area, and significant doubt exists about whether a 
population ever occurred there historically (COSEWIC 2003, p. 20). For 
the purposes of this finding, we considered the Canadian wolverine 
population to include only wolverines from Ontario west to the Pacific 
coast and Alaska, and assumed that wolverines in eastern Canada were 
either extirpated or are at such low numbers as not to be part of a 
functioning population. It is our determination that the conservation 
status of the eastern population, if it does indeed exist, is not 
relevant to the discreteness analysis for this DPS for the following 
reasons: (1) If wolverines currently reside in the eastern Canadian 
Provinces, they are likely disjunct from wolverines in western Canada 
(COSEWIC 2003, Figure 3); and (2) there is significant doubt that 
wolverine populations existed in this part of Canada historically, so 
the current lack of evidence of a population may not represent a 
degradation of species status in this area (COSEWIC 2003, pp. 20-21).
    The second substantial difference in wolverine status between the 
contiguous United States and Canada is reflected in the size of the 
effective populations. 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. For 
populations where contribution to the next generations is often 
unequal, effective population size will be smaller than the true or 
``census'' population size. The smaller the effective population size, 
the more reproduction is dominated by a few individuals. Effective 
population size is important because it determines rates of loss of 
genetic variation, fixation of deleterious alleles and the rate of 
inbreeding. Populations with small effective population sizes show 
reductions in population growth rates and increases in extinction 
probabilities (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, 
p. 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 (for appropriate use of this rule and 
its limitations see Allendorf and Luikart 2007, pp. 359-360). Others 
suggest that even higher numbers are required to ensure that 
populations remain viable, suggesting that long-term connectivity to 
the reservoir of genetic resources in the Canadian population of 
wolverines will be required (Traill et al. 2010, p. 32).
    Wolverine effective population size in the largest extant 
population in the contiguous United States is exceptionally low 
(Schwartz personal communication 2007, entire) and is below what is 
thought necessary for short-term maintenance of genetic diversity. 
Effective population size for wolverines in the Rocky Mountains 
averaged 39 (Schwartz personal communication 2007, entire) (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 Mountain population. Thus, 
wolverine effective population sizes are very low. For comparison, 
estimates of wolverine effective population size are bracketed by 
critically endangered species like the black-footed ferret (4.10) 
(Wisely et al.

[[Page 78038]]

2007, p. 3) and ocelots (2.9 to 13.9) (Janecka et al. 2007, p. 1), but 
substantially smaller than estimates for the Yellowstone Grizzly bear 
(greater than 100), which has reached the level of recovery under the 
Act (Miller and Waits 2003, p. 4338). Therefore, we conclude that 
effective population size estimates for wolverines do not suggest that 
populations are currently critically endangered, but they do suggest 
that populations are low enough that they could be vulnerable to loss 
of genetic diversity, and may require intervention in the future to 
remain viable.
    The concern with the low effective population size is highlighted 
in recent research that determined that, absent immigration, at least 
400 breeding pairs would be necessary to sustain long-term genetic 
viability of the contiguous U.S. wolverine population (Cegelski et al. 
2006, p. 197). However, the entire population is likely 250-300 (Inman 
2010b, pers. comm.), with a substantial number of these being 
nonbreeding subadults. Furthermore, the U.S. population appears to be 
split into at least five smaller subpopulations (Northern Cascades, 
CrazyBelts, Idaho, Greater Yellowstone Ecosystem, and Northern Montana) 
that are semi-isolated from each other, meaning that genetic exchange 
does not occur frequently enough to prevent genetic drift (changes in 
genetic composition due to random sampling in small populations) and 
loss of genetic diversity (Cegelski et al. 2006, p. 206) further 
reducing the effective population size. Based on available scientific 
and commercial information, it does not appear that any of the 
wolverine populations that historically existed in the contiguous 
United States would have had effective population sizes approaching 400 
animals. Therefore, it is likely that connectivity to Canadian 
populations to the north would have been necessary to maintain genetic 
diversity in these populations prior to European settlement.
    The concern that low effective population size may result in 
negative effects is already being realized for the contiguous U.S. 
population of wolverine. Genetic drift has occurred in the remaining 
populations in the contiguous United States: wolverines here contain 3 
of 13 haplotypes (sets of closely linked genetic markers that are 
inherited together) 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 populations are a subset of those 
in the larger Canadian population, indicating that genetic drift had 
caused a loss of genetic diversity. A single haplotype dominates the 
northern Rocky Mountain wolverine population, with 71 of 73 wolverine 
sampled expressing that haplotype (Schwartz et al. 2007, p. 2176). The 
reduced number of haplotypes indicates not only that genetic drift is 
occurring, but also that there is some level of genetic separation; if 
these populations were freely interbreeding, they would share more 
haplotypes. The reduction of haplotypes is likely a result of small 
population size and 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). 
Whether or not the wolverine population in the contiguous United States 
has suffered any deleterious effects due to this reduction in genetic 
diversity is unknown. However, based on principles of conservation 
genetics, we do expect that reduced genetic diversity would make this 
population more vulnerable to other threats due to reduced genetic 
resiliency and reduced ability to adapt to change (Allendorf and 
Luikart 2007, pp. 338-342).
    No effective population size estimate ex