83726 Federal Register / Vol. 88, No. 229 / Thursday, November 30, 2023 / Rules and Regulations 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–R6–ES–2023–0216; 

FF09E21000 FXES11110900000 245] 

RIN 1018–BH27 

Endangered and Threatened Wildlife 

and Plants; Threatened Species Status 

With Section 4(d) Rule for North 

American Wolverine 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Final rule and interim rule with 

request for comments. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), determine 

threatened species status under the 

Endangered Species Act of 1973 (Act), 

as amended, for the distinct population 

segment (DPS) of the North American 

wolverine (Gulo gulo luscus) occurring 

in the contiguous United States. This 

rule adds the contiguous U.S. DPS of the 

North American wolverine to the 

Federal List of Endangered and 

Threatened Wildlife. We are also issuing 

an interim rule under the authority of 

section 4(d) of the Act (an ‘‘interim 4(d) 

rule’’) that provides the prohibitions, 

and exceptions to those prohibitions, 

necessary and advisable for the 

conservation of the contiguous U.S. DPS 

of the North American wolverine. 

DATES: 

Effective date: This rule is effective 

January 2, 2024. 

Comments due: Comments on the 

interim 4(d) rule must be received or 

postmarked by January 29, 2024. 

ADDRESSES: 

Written comments on the interim 4(d) 

rule: You may submit comments on the 

interim 4(d) rule by one of the following 

methods: 

(1) Electronically: Go to the Federal 

eRulemaking Portal: https://

www.regulations.gov. In the Search box, 

enter FWS–R6–ES–2023–0216, which is 

the docket number for this rulemaking. 

Then click on the Search button. On the 

resulting page, in the panel on the left 

side of the screen, under the Document 

Type heading, click on the Rules box to 

locate this document. You may submit 

a comment by clicking on ‘‘Comment.’’ 

(2) By hard copy: U.S. mail: Public 

Comments Processing, Attn: FWS–R6– 

ES–2023–0216; U.S. Fish and Wildlife 

Service; MS: PRB/3W; 5275 Leesburg 

Pike; Falls Church, VA 22041–3803. 

We will post all comments on https:// 

www.regulations.gov. This generally 

means that we will post any personal 

information you provide us (see Public 

Comments Solicited on the Interim 4(d) 

Rule, below, for more information). 

Availability of supporting materials: 

This document is available on the 

internet at https://www.regulations.gov 

and at https://ecos.fws.gov/ecp/species/ 

5123. Supporting materials we used in 

preparing this rule, including the 2018 

species status assessment (SSA) report 

and the 2023 addendum to the SSA 

report, are available on the Service’s 

website at https://ecos.fws.gov/ecp/ 

species/5123, at https://

www.regulations.gov at Docket No. 

FWS–R6–ES–2023–0216, or both. 

FOR FURTHER INFORMATION CONTACT: Jodi 

Bush, U.S. Fish and Wildlife Service, 

Pacific Region, 911 NE 11th Ave., 

Portland, OR 97232; telephone: (503) 

231–6131. Individuals in the United 

States who are deaf, deafblind, hard of 

hearing, or have a speech disability may 

dial 711 (TTY, TDD, or TeleBraille) to 

access telecommunications relay 

services. Individuals outside the United 

States should use the relay services 

offered within their country to make 

international calls to the point-ofcontact in the United States. 

SUPPLEMENTARY INFORMATION: 

Executive Summary 

Final Rule To List the Contiguous U.S. 

DPS of the North American Wolverine 

Why we need to publish a rule. The 

Act (16 U.S.C. 1531 et seq.) defines 

‘‘species’’ as any subspecies of fish or 

wildlife or plants, and any distinct 

population segment (DPS) of any 

species of vertebrate fish or wildlife 

which interbreeds when mature. Under 

the Act, a species warrants listing if it 

meets the definition of an endangered 

species (in danger of extinction 

throughout all or a significant portion of 

its range) or a threatened species (likely 

to become an endangered species within 

the foreseeable future throughout all or 

a significant portion of its range). If we 

determine that a species warrants 

listing, we must list the species 

promptly and designate the species’ 

critical habitat to the maximum extent 

prudent and determinable. We have 

determined that the DPS of the North 

American wolverine occurring in the 

contiguous United States (the 

‘‘contiguous U.S. DPS’’) meets the Act’s 

definition of a threatened species; 

therefore, we are listing it as such. 

Listing a species as an endangered or 

threatened species can be completed 

only by issuing a rule through the 

Administrative Procedure Act 

rulemaking process (5 U.S.C. 551 et 

seq.). 

What this document does. This 

document is both (1) a final rule listing 

the contiguous U.S. DPS of the North 

American wolverine as a threatened 

species under the Act; and (2) an 

interim rule issued under the authority 

of section 4(d) of the Act (an ‘‘interim 

4(d) rule’’) providing the prohibitions, 

and exceptions to those prohibitions, 

that are necessary and advisable to 

provide for the conservation of the 

contiguous U.S. DPS of the North 

American wolverine. 

The basis for our action. Under the 

Act, we may determine that a species is 

an endangered or threatened species 

because of any of five factors: (A) The 

present or threatened destruction, 

modification, or curtailment of its 

habitat or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) the inadequacy of 

existing regulatory mechanisms; or (E) 

other natural or manmade factors 

affecting its continued existence. We 

have determined that the contiguous 

U.S. DPS of the North American 

wolverine is a threatened species due 

primarily to the ongoing and increasing 

impacts of climate change and 

associated habitat degradation and 

fragmentation. 

Section 4(a)(3) of the Act requires the 

Secretary of the Interior (Secretary) to 

designate critical habitat concurrent 

with listing to the maximum extent 

prudent and determinable. We have not 

yet obtained the necessary economic 

information needed to develop a 

proposed critical habitat designation for 

the contiguous U.S. DPS of the North 

American wolverine. Therefore, we find 

that designation of critical habitat for 

the DPS is currently not determinable. 

Interim 4(d) Rule 

The need for the regulatory action 

and how the action will meet that need. 

Consistent with section 4(d) of the Act, 

this interim 4(d) rule provides measures 

that are tailored to our current 

understanding of the conservation needs 

of the North American wolverine. 

Under section 4(d) of the Act, the 

Secretary of the Interior has discretion 

to issue such regulations as she deems 

necessary and advisable to provide for 

the conservation of the species. The 

Secretary also has the discretion to 

prohibit by regulation with respect to a 

threatened species, any act prohibited 

by section 9(a)(1) of the Act. 

Summary of the major provisions of 

the regulatory action. This interim 4(d) 

rule will provide for the conservation of 

the contiguous U.S. DPS of the North 

American wolverine by prohibiting the 

following activities, unless they fall 


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within the specific identified exceptions 

or are otherwise authorized or 

permitted: importing or exporting; take; 

possession and other acts with 

unlawfully taken specimens; delivering, 

receiving, carrying, transporting, or 

shipping in interstate or foreign 

commerce in the course of commercial 

activity; or selling or offering for sale in 

interstate or foreign commerce. 

The interim 4(d) rule will also 

provide for the conservation of the 

species by allowing exceptions to the 

general prohibitions against ‘‘take’’ of 

the species in support of conservation 

actions and otherwise lawful activities 

that could take wolverines but at 

minimal levels not likely to have a 

negative impact on the species’ 

conservation. The exceptions include 

take due to scientific research 

conducted on wolverines by a Federal 

or Tribal biologist in the course of their 

official duties, incidental take resulting 

from forest management activities for 

the purposes of reducing the risk or 

severity of wildfire, and incidental take 

resulting from legal trapping conducted 

consistent with State and Tribal 

trapping rules or guidelines that contain 

steps to minimize the potential for 

capture of wolverine. 

Supporting Documents 

A team prepared a species status 

assessment (SSA) for the North 

American wolverine (Gulo gulo luscus) 

(Service 2018, entire) (hereafter referred 

to as the wolverine SSA report). The 

SSA team was composed of U.S. Fish 

and Wildlife Service (Service) 

biologists, who consulted with other 

species experts. The wolverine SSA 

report represented a compilation of the 

best scientific and commercial data 

available (known at that time) 

concerning the status of the North 

American wolverine, including the 

impacts of past, present, and future 

factors (both negative and beneficial) 

affecting the wolverine. The wolverine 

SSA report underwent independent 

peer review by scientists with 

experience with mesocarnivores and 

their conservation and management, 

genetics, population modeling, and 

climate change. 

More recently, the Service prepared 

an SSA addendum for the North 

American wolverine (Gulo gulo luscus) 

(Service 2023, entire) (hereafter referred 

to as the wolverine SSA report 

addendum). The wolverine SSA report 

addendum contains a synthesis of 

relevant new information that has 

become available since the 2018 

wolverine SSA report. The wolverine 

SSA report addendum underwent 

independent peer review by scientists 

with experience with mesocarnivores 

and their conservation and 

management, genetics, population 

modeling, and climate change. The 

wolverine SSA report addendum also 

underwent technical review by State, 

Federal, and Tribal biologists. 

The wolverine SSA report, the 

wolverine SSA report addendum, and 

other materials relating to this 

rulemaking can be found at the Service’s 

website at https://ecos.fws.gov/ecp/ 

species/5123, and at https://

www.regulations.gov at Docket No. 

FWS–R6–ES–2023–0216. 

Previous Federal Actions 

On February 4, 2013, we published in 

the Federal Register (78 FR 7864) a 

proposed rule to list the DPS of the 

North American wolverine occurring in 

the contiguous United States as a 

threatened species under the Act, with 

a proposed rule under section 4(d) of 

the Act that outlined the prohibitions, 

and exceptions to those prohibitions, 

necessary and advisable for the 

conservation of the wolverine. Please 

refer to that February 4, 2013, proposed 

rule (78 FR 7864) for a detailed 

description of previous Federal actions 

concerning the wolverine prior to 2013. 

We published a separate proposed rule 

in the Federal Register on February 4, 

2013 (78 FR 7890), to establish a 

nonessential experimental population 

(NEP) area for the North American 

wolverine in the Southern Rocky 

Mountains of Colorado, northern New 

Mexico, and southern Wyoming. On 

October 31, 2013, we reopened the 

comment period on the proposed listing 

rule for an additional 30 days (78 FR 

65248). 

Following publication of the 2013 

proposed rules, there was scientific 

disagreement and debate about the 

interpretation of the habitat 

requirements for wolverines and 

available climate change information 

used to determine the extent of threats 

to the contiguous U.S. DPS of the North 

American wolverine. Based on this 

substantial disagreement regarding the 

sufficiency or accuracy of the available 

data relevant to the proposed listing, on 

February 5, 2014, we announced in the 

Federal Register (79 FR 6874) a 6-month 

extension of the final determination of 

whether to list the contiguous U.S. DPS 

of North American wolverine as a 

threatened species under the Act. That 

document reopened the comment 

period on the February 4, 2013, 

proposed listing rule for an additional 

90 days. 

On August 13, 2014, we published in 

the Federal Register (79 FR 47522) a 

document withdrawing both proposed 

rules published on February 4, 2013: (1) 

the proposed rule to list the contiguous 

U.S. DPS of the North American 

wolverine as a threatened species under 

the Act, including the provisions 

proposed under section 4(d) of the Act; 

and (2) the proposed NEP designation 

under section 10(j) of the Act for the 

North American wolverine in the 

Southern Rocky Mountains of Colorado, 

northern New Mexico, and southern 

Wyoming. These withdrawals were 

based on our conclusion that the factors 

affecting the DPS as identified in the 

listing proposed rule were not as 

significant as believed at the time of that 

proposed rule’s publication in 2013. 

In October 2014, three complaints 

were filed in the District Court for the 

District of Montana by Defenders of 

Wildlife, WildEarth Guardians, Center 

for Biological Diversity, and other 

organizations challenging the 

withdrawal of the February 4, 2013, 

proposed rule to list the contiguous U.S. 

DPS of the North American wolverine. 

Numerous parties intervened in the 

litigation. These three cases were 

consolidated, and on April 4, 2016, the 

court issued a decision. The court 

granted plaintiffs’ motion for summary 

judgment with respect to the Service’s 

determination regarding (1) the threat 

posed to the wolverine by the effects of 

climate change at the reproductive 

denning scale, (2) the threat posed to the 

wolverine by small population size and 

lack of genetic diversity, and (3) the 

application of the significant portion of 

the range policy to the wolverine. As a 

result of the court order, the August 13, 

2014, withdrawal (79 FR 47522) of the 

February 4, 2013, proposed listing rule 

was vacated and remanded to the 

Service for further consideration 

consistent with the order. 

In effect, the court’s action returned 

the process to the proposed rule stage, 

and the status of the contiguous U.S. 

DPS of the North American wolverine 

under the Act reverted to that of a 

proposed species for the purposes of 

consultation under section 7 of the Act. 

On October 18, 2016, we published in 

the Federal Register (81 FR 71670) a 

document reopening the comment 

period on the February 4, 2013, 

proposed rule to list the DPS of the 

North American wolverine occurring in 

the contiguous United States as 

threatened under the Act (78 FR 7864). 

The October 18, 2016, publication also 

requested new information and 

announced that we were initiating a 

new and comprehensive status review 

of the North American wolverine, to 

determine whether the species meets 

the definition of an endangered or 

threatened species under the Act, or 


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whether the species is not warranted for 

listing. Both new and updated 

information and analyses presented in 

the wolverine 2018 SSA report, along 

with public comments, prompted us to 

reevaluate our previous assessment of 

the DPS (presented in our 2013 

proposed listing rule (78 FR 7864), 

which in turn relied on the DPS analysis 

completed in our 2010 12-month 

finding (75 FR 78030)) with respect to 

the North American wolverine in the 

contiguous United States. 

On October 13, 2020, we published in 

the Federal Register (85 FR 64618) 

another document withdrawing the 

February 4, 2013, proposed rule to list 

the DPS of the North American 

wolverine occurring in the contiguous 

United States as threatened under the 

Act. Our 2020 withdrawal decision was 

based on our conclusion that the factors 

affecting the North American wolverine 

occurring in the contiguous United 

States as identified in the 2013 

proposed listing rule were not as 

significant as believed at the time of the 

proposed rule’s publication in 2013. We 

also found that the North American 

wolverines occurring in the contiguous 

United States did not qualify as a DPS. 

The Center for Biological Diversity 

and WildEarth Guardians filed lawsuits 

in the District Court for the District of 

Montana challenging the Service’s 2020 

decision to withdraw the February 4, 

2013, proposal to list the contiguous 

U.S. DPS of the North American 

wolverine. The cases were consolidated, 

and the State of Idaho’s motion to 

intervene was granted. On February 4, 

2022, the Service filed a motion asking 

the court to voluntarily return (remand) 

the 2020 withdrawal decision to the 

Service to allow the Service to reexamine the decision in light of the 

intervening decision in Center for 

Biological Diversity v. Haaland, 998 

F.3d 1061 (9th Cir. 2021) (‘‘Pacific 

Walrus Decision’’) and to reevaluate the 

decision in light of new scientific 

information that had become available 

since the completion of the 2018 SSA. 

The Service also requested that the 2020 

withdrawal decision remain in effect 

pending that reevaluation. On May 26, 

2022, the court granted the Service’s 

request for a voluntary remand of the 

2020 withdrawal decision, but the court 

decided to vacate the withdrawal 

decision (Ctr. for Biological Diversity v. 

Haaland, No. CV 20–181–M–DWM (D. 

Mont. May 26, 2022)). 

The court’s May 26, 2022, action 

returned the listing process for the 

North American wolverine to the 

proposed rule stage. On November 23, 

2022, the Service published in the 

Federal Register (87 FR 71557) a 

document soliciting new information on 

the North American wolverine and 

notifying the public that the February 4, 

2013, proposed rule to list the 

contiguous U.S. DPS of the North 

American wolverine as threatened 

under the Act (78 FR 7864) had been 

reinstated. As of May 26, 2022, for 

purposes of consultation under section 

7 of the Act, the North American 

wolverine was again a species proposed 

for listing and subject to conferencing 

requirements. 

The Service then completed the 

wolverine SSA report addendum 

(Service 2023, entire), which contains a 

synthesis of all relevant new 

information that has become available 

since the 2018 wolverine SSA report to 

inform this final listing rule and the 

associated interim 4(d) rule. 

Peer Review 

Our assessment of the status of the 

North American wolverine contained in 

this document is supported by 

information in both the 2018 SSA report 

(Service 2018, entire) and the 2023 

wolverine SSA report addendum 

(Service 2023, entire). In accordance 

with our joint policy on peer review 

published in the Federal Register on 

July 1, 1994 (59 FR 34270), and our 

August 22, 2016, memorandum 

updating and clarifying the role of peer 

review in listing actions under the Act, 

we solicited independent scientific 

review of the information contained in 

the 2018 wolverine SSA report. We sent 

the SSA report to four independent peer 

reviewers and received four responses; 

we incorporated the results of that 

review into the SSA report, as 

appropriate. More recently, we solicited 

independent scientific review of the 

2023 wolverine SSA report addendum. 

We sent the wolverine SSA report 

addendum to six peer reviewers and 

received three responses; we 

incorporated the results of the peer 

review into the wolverine SSA report 

addendum, as appropriate. The peer 

reviews on the wolverine SSA report 

and the wolverine SSA report 

addendum can be found at https://

www.regulations.gov. 

Summary of Changes 

Since the publication of the February 

4, 2013, proposed listing rule (78 FR 

7864), the development of the 2018 SSA 

report (Service 2018, entire), and the 

publication of the October 13, 2020, 

withdrawal document (85 FR 64618), a 

substantial number of new studies have 

become available, refining our 

understanding of wolverine biology and 

threats affecting North American 

wolverines in the contiguous United 

States. We incorporated this new 

information into the 2023 wolverine 

SSA report addendum. We summarize 

the information most salient to our 

determination in this final rule below. 

We also discuss these changes where 

appropriate in the remainder of the 

document to provide further detail and 

context. 

Ecological Requirements 

The snow model used in the climate 

change analysis in the 2018 SSA report 

and October 13, 2020, withdrawal 

document (85 FR 64618) projected snow 

loss out to year 2050 in only two 

modeling domains (Glacier National 

Park and the central Rocky Mountains) 

(Service 2018, p. 88). Results indicated 

a decline in spring snow in these areas 

due to climate change was likely, but we 

were unable to extrapolate those 

projections across the remainder of the 

North American wolverine’s breeding 

range in the contiguous United States. 

Persistent spring snow (greater than or 

equal to 1 meter on May 1; see Climate 

Change, below) was not identified as an 

ecological requirement for wolverines, 

and we assumed that if snow was 

necessary for denning, there would be 

enough spring snowpack in the future to 

fulfill denning needs. 

Our updated climate analysis reported 

in the 2023 wolverine SSA report 

addendum projects snow loss out to 

2100 across five modeling domains that 

cover a much larger extent of the 

breeding range in the contiguous United 

States when compared to the 2018 SSA 

report. In our 2023 wolverine SSA 

report addendum, we found declines in 

spring snow due to climate change are 

likely across the North American 

wolverine’s range and predicted losses 

will be greater in 2100 than in 2050. In 

general, when compared to historical 

amounts of snow cover, nearly every 

area modeled (except for the MidRockies) sees a decrease in snow cover 

and that decrease becomes larger over 

time. In the Mid-Rockies, snow cover 

increases in the short term, but as with 

the other areas, it decreases over time. 

New research indicates that areas 

characterized by persistent spring snow 

are likely important for wolverine 

survival (e.g., caching food) in addition 

to denning and reproduction. One new 

study reported wolverines cache food 

year-round, indicating that warmer 

temperatures could impact the ability of 

wolverines to store food resources by 

decreasing the shelf-life (usability) of 

cached food, and increasing competition 

from pilferers that benefit from a 

warmer climate (van der Veen et al. 

2020, p. 1). Another study found 

evidence to support a functional 


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relationship between North American 

wolverines and persistent spring snow 

that could be explained by the 

distribution of food, disturbance, or 

mortality risk (Kortello et al. 2019, p. 8). 

Connectivity With Canada 

Connectivity with Canada is essential 

to the long-term viability of North 

American wolverines in the contiguous 

United States (Cegelski et al. 2006, p. 

209). In the 2018 SSA report and 

October 13, 2020, withdrawal document 

(85 FR 64618), we assumed that 

wolverines could move freely between 

Canada and the United States (Service 

2018, p. 104). We also concluded that 

trapping of wolverines did not represent 

a barrier to wolverine movement and 

dispersal along the international border 

(Service 2018, p. 69). Additionally, we 

concluded that major highways did not 

represent a barrier to wolverine 

movement (Service 2018, p. 60). 

In the 2023 wolverine SSA report 

addendum, we affirm that connectivity 

with Canada is essential to the longterm viability of North American 

wolverines in the lower 48 States. 

However, our understanding of the 

ability of wolverines to move between 

Canada and the United States in the 

Rocky Mountains has changed. New 

research found an estimated 41 percent 

decline in the wolverine population 

from 2011–2020 in a portion (7,583,417 

acres (ac) (30,689 square kilometers 

(km2))) of the southern Canadian 

Rockies, Purcell Mountains, and Selkirk 

Mountains important for wolverine 

connectivity with the United States; this 

decline could be attributed to one or 

more of the following causes: trapping, 

backcountry recreation, human 

development, and food availability 

(Barrueto et al. 2022, p. 4). In addition, 

new transboundary genetic research 

indicates the Trans-Canada Highway in 

southern British Columbia is impeding 

female dispersal from Canada to the 

United States, thereby limiting gene 

flow and the ability of dispersing 

wolverines to supplement the 

contiguous U.S. DPS (Sawaya et al. 

2023, pp. 12, 17). 

Genetic Diversity and Adaptive Capacity 

In the October 13, 2020, withdrawal 

document (85 FR 64618), we found 

there was no available information to 

indicate that the current abundance of 

the North American wolverine across its 

range in the contiguous United States 

was at a level that was causing 

inbreeding depression or loss of genetic 

variation that would affect its ability to 

adapt to changing conditions. 

New transboundary genetic research 

shows a sharp decline in genetic 

diversity and increasing population 

fragmentation at the southern extent of 

the North American wolverine’s range 

in western North America (Sawaya et al. 

2023, p. 17). As a result, there is 

potential for inbreeding given the 

relatively small population sizes and 

low levels of genetic diversity of 

wolverines in the contiguous United 

States, especially in the Cascade 

Mountains of Washington and southern 

British Columbia (Sawaya 2023, pers. 

comm.); however, inbreeding 

depression has not been observed. New 

analysis of the North American 

wolverine’s adaptive capacity shows 

that their specialized habitat 

associations, low genetic diversity and 

population size, narrow ecological 

niche, low tolerance for human 

disturbance, and slow reproductive rate 

all contribute to the wolverine’s relative 

difficulty in adapting in-place to future 

environmental change (Service 2023, p. 

66). 

Roads and Development 

We analyzed the effects of roads and 

development (human disturbance) to 

North American wolverines in the 2018 

SSA report (Service 2018, p. 62) and 

determined in our October 13, 2020, 

withdrawal document (85 FR 64618) 

that impacts to wolverines are small and 

narrow in scope and scale. We did not 

consider roads and development to be 

an impediment to wolverine movement 

and gene flow. 

New habitat and landscape genetic 

research indicates multi-lane roads and 

human development in valley bottoms 

between core habitats may limit 

dispersal and population connectivity to 

some extent, especially for female 

wolverines. Connectivity among 

wolverine habitats appears to be 

particularly sensitive to housing 

developments (Balkenhol et al. 2020, p. 

797). Also, new research indicates that 

human disturbance (road density) and 

food availability are major drivers of 

wolverine distribution in winter 

(Kortello et al. 2019, p. 1). Wolverine 

density and detection probability 

declined in areas with more human 

development (Barrueto et al. 2022, p. 4). 

Human development may also have 

cascading impacts of increasing 

competition from other mesocarnivores 

that are less affected by human 

disturbance (Frey et al. 2020, pp. 1136– 

1138; Chow-Fraser et al. 2022, p. 6; 

Milanesi et al. 2022, pp. 10–11). 

Winter Recreation 

In our 2018 SSA report and October 

13, 2020, withdrawal document (85 FR 

64618), we concluded that winter 

recreation is a low-level stressor for 

wolverines in the contiguous United 

States (Service 2018, p. 62). The limited 

research available at the time indicated 

some avoidance behavior exhibited by 

wolverines in areas with backcountry 

winter recreation, but not to the extent 

that we had concerns about populationlevel impacts. 

In the 2023 wolverine SSA report 

addendum, we provide an updated 

assessment of the effects of winter 

recreation based on new studies. 

Research indicates winter recreation is 

negatively associated with North 

American wolverine habitat use, and 

that winter recreation is likely to 

increase and become more concentrated 

in the future as snow-covered areas 

decline due to climate change 

(Heinemeyer et al. 2019, p. 1). A large 

multi-State analysis of winter recreation 

impacts in the Northern Rocky 

Mountains was published in 2019, 

indicating greater concern for impacts to 

wolverines than we found in 2018 and 

showing a negative functional response 

to the level of recreation exposure 

within their home ranges (Heinemeyer 

et al. 2019a, pp. 13–14, 17–18). 

Additionally, new research found an 

incremental loss of wolverines in 

portions of central Idaho where winter 

recreation impacts are increasing (Mack 

and Hagan 2022, p. 13). Furthermore, 

forest roads used by snowmobilers in 

the Canadian Rockies were found to 

have a strong negative correlation with 

wolverine distribution (Kortello et al. 

2019, p. 10). Wolverine detection 

probability in protected and nonprotected habitat of southwestern 

Canada was found to be strongly and 

negatively correlated with 

nonmotorized recreation in summer and 

winter (Barrueto et al. 2022, p. 5). 

Trapping 

In our 2018 SSA and the October 13, 

2020, withdrawal document (85 FR 

64618), we concluded that 

overutilization does not currently 

represent a stressor to the North 

American wolverine in the contiguous 

United States at the individual, 

population, or species level. We also 

concluded that trapping in Canada has 

been and appears to be sustainable, and 

trapping or harvesting of wolverines 

along the contiguous U.S.–Canada 

border does not represent a stressor to 

wolverines migrating into the 

contiguous United States and does not 

represent a barrier to wolverine 

movement and dispersal along the 

international border (Service 2018, p. 

71). 

Legal trapping of wolverines has not 

occurred in the contiguous United 

States in the past 10 years, and lethal 


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incidental trapping of wolverines has 

been minimal (Service 2023, p. 38). We 

expect recent changes to wolf trapping 

regulations in Idaho and Montana to 

have little effect on wolverines at a 

population level, as long as trapping is 

done in a manner to limit wolverine 

bycatch (Idaho Department of Fish and 

Game (IDFG) 2023, in litt., p. 1; IDFG 

2022, p. 40; Montana Fish, Wildlife and 

Parks (MFWP) 2023, in litt., p. 1; MFWP 

2022, entire). Below, under 

Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes, we provide an assessment of 

incidental trapping and the measures 

States are taking to reduce incidental 

trapping of wolverines. 

Recent research on wolverine 

trapping in Southern Canada indicates 

that trapping may be having more of a 

negative effect on wolverine 

populations in Canada than previously 

thought (Kortello et al. 2019, pp. 1, 10; 

Mowat et al. 2020, entire; Barrueto et al. 

2020, p. 296; Barrueto et al. 2022, 

entire). Unsustainable trapping levels in 

Canada could limit dispersal of 

individuals into the contiguous United 

States, where the dispersal of 

wolverines from Southern Canada is 

vital to the genetic and demographic 

health of the U.S. population (Sawaya 

2023, pers. comm.). 

Summary of Comments and 

Recommendations 

Comments on the 2013 Proposed Listing 

Rule 

Upon publication of our February 4, 

2013, proposed rule to list the DPS of 

North American wolverine occurring in 

the contiguous United States as a 

threatened species (78 FR 7864), we 

opened a 90-day public comment 

period, ending May 6, 2013. After we 

withdrew the proposed rule, on October 

18, 2016 (81 FR 71670), we again 

opened a public comment period on our 

2013 proposed listing rule; that 

comment period was open for 30 days, 

ending November 17, 2016. At both 

times, we contacted appropriate Federal 

and State agencies, scientific experts 

and organizations, Tribes, and other 

interested parties and invited them to 

comment on the 2013 proposed listing 

rule. Many of the comments we received 

from State agencies during our 2016 

reopened comment period (81 FR 

71670) were similar to those we 

received during the initial 2013 public 

comment period (78 FR 7864). All 

substantive information provided 

during both comment periods on our 

2013 proposed listing rule has either 

been incorporated directly into this final 

determination or is addressed below. 

Below, we present the comments 

received on the 2013 proposed listing 

rule and a summary of our responses as 

presented in the October 13, 2020, 

withdrawal document (85 FR 64618). 

We also provide updated responses to 

several of the comments based on new 

information presented in the 2023 

wolverine SSA report addendum and 

this final rule. Comments are numbered 

below as they were numbered in the 

October 13, 2020, withdrawal document 

(85 FR 64618). Several of the comments 

and responses from the October 13, 

2020, withdrawal document did not 

require revision, and they are 

incorporated here by reference; those 

comments with responses that remain 

the same are comments 6, 7, 9, 11, 13, 

20, 21, 22, 23, and 24 (85 FR 64618 at 

64622–64626). 

Public Comments 

(1) Comment: We received several 

public comments claiming that the 

North American wolverine faces 

increasing threats from the effects of 

climate change, particularly habitat loss 

due to declining snowpack. 

Our 2020 Response Summarized: Our 

climate assessment in the 2018 

wolverine SSA report and October 13, 

2020, withdrawal document focused on 

the impact of climate change to denning 

conditions for wolverines. We stated we 

recognize that current climate trends 

and future (2055 and later) climate 

model projections indicate warming 

temperatures for much of western North 

America and changes to snow-pack 

conditions. In general, models indicate 

higher elevations, where documented 

historical wolverine denning has 

occurred, will retain more snow cover 

than lower elevations, particularly in 

early spring (on April 30/May 1). We 

referenced a climate analysis that 

included two regions, Glacier National 

Park and Rocky Mountain National 

Park. Details of this climate analysis are 

presented in Ray et al. (2017) and are 

summarized in the 2018 SSA report. 

Climate models in Ray et al. (2017) built 

upon previous model projections 

presented in McKelvey et al. (2011), but 

with significant differences such as finer 

spatial resolution, incorporation of 

slope and aspect, snow depth estimates, 

additional years of historical data, and 

wider temporal analyses of snow 

persistence (April–June). Model 

projections from Ray et al. (2017) 

indicate significant areas (several 

hundred square kilometers (km2)/square 

miles (mi2) for each study area) of future 

snow (greater than 0.5 meters (m) (20 

inches (in)) in depth) are likely to 

persist on May 1 at elevations currently 

used by wolverines for denning. This is 

true, on average, across the range of 

climate models used out to 

approximately year 2055. 

Our 2023 Response: Our assessment 

of climate change impacts to North 

American wolverines in the 2023 

wolverine SSA report addendum, and 

applied in this final rule, evaluates the 

impact of climate warming and changes 

in snowpack on various aspects of 

wolverine ecology, not just denning 

habitat (see Climate Change, below). We 

now consider habitats characterized by 

the presence of persistent spring snow 

for survival and reproduction to be a 

physical and ecological requirement for 

wolverines in the contiguous United 

States (see Life-History Needs, below). 

New evidence from around the world 

reinforces that snow—especially 

persistent spring snow—is an important 

predictor of broad-scale wolverine 

distribution and density (Aubry et al. 

2023, pp. 15–16; Carroll et al. 2020, p. 

8; Fisher et al. 2022, p. 10; Glass et al. 

2021, entire; Mowat et al. 2020, p. 220). 

Snow cover appears to influence 

wolverine dispersal and resulting 

genetic structure (Balkenhol et al. 2020, 

pp. 798–799). Warming future 

conditions could make caching food 

more difficult for wolverines year-round 

(Van der Veen et al. 2020, pp. 8–10). 

Climate change also has the potential to 

exacerbate the impacts of other 

stressors, including effects from roads, 

winter recreational activity, 

development, low genetic diversity, and 

small populations (see Threats, below). 

Wolverines have denned outside of 

spring snowpack in the boreal forests of 

Canada and Scandinavia; however, the 

importance of spring snow for denning 

may vary among areas depending on the 

abundance of alternative den site 

structures, competitors, and food 

resources (Persson et al. 2023, p. 5810). 

Furthermore, there is no evidence that 

North American wolverines have 

denned in areas outside of spring 

snowpack in their alpine habitats in the 

contiguous United States. In light of 

this, we do not expect North American 

wolverines to continue to have the same 

or better resiliency in the contiguous 

United States in the future when cold 

and snowy conditions are expected to 

decrease, with spring snowpack 

decreasing as much as 50 percent in 

some areas. Although we are not seeing 

deleterious effects of climate change on 

the contiguous U.S. population of North 

American wolverines currently, we 

expect future impacts at the population 

level. For further detail, see the 

discussion under Climate Change, 

below. 

(2) Comment: We received several 

public comments during our request for 


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information claiming that low 

population size (and small effective 

population size) warrant listing of the 

North American wolverine as 

threatened or endangered. 

Our 2020 Response Summarized: We 

stated that wolverines are difficult 

animals to survey, and populations 

occur in naturally low densities across 

their North American range, due in large 

part to their need for large, exclusive 

territories. At that time (and still today), 

the only estimate of the number of 

wolverines that currently occupy the 

contiguous United States is the oftencited population estimate of 318 

wolverines (range: 249–926) in the 

contiguous United States. This estimate 

was derived from habitat modeling 

presented in Inman et al. (2013). That 

publication also provided a modeled 

estimate of potential wolverine capacity 

in the contiguous United States of 644 

wolverines (range: 506–1881). We also 

reported the preliminary results from 

the Western States Wolverine 

Conservation Project (WSWCP) 

occupancy study in four western States 

(Idaho, Montana, Washington, and 

Wyoming) and from a pilot occupancy 

study in Wyoming (2015–2016) (Service 

2018, appendix B). Preliminary analysis 

of the study results indicated an average 

estimated probability of occupancy of 

0.42, suggesting that wolverines used 

nearly half of all sites during the study 

period (MFWP 2017, pers. comm.). 

Although the sum of these reports 

cannot confirm the previous estimate of 

population size or verify population 

trends, they offer recent evidence that 

wolverines continue to be observed 

across a large area of the western United 

States. 

We also discussed the estimated 

effective population size by Schwartz et 

al. (2009), which estimated a summed 

effective population size of 35, with 

credible limits from 28 to 52 (Schwartz 

et al. 2009, p. 3,226). We stated that the 

analysis missed two wolverine 

subpopulations as well as individuals, 

which would underestimate the results 

for this type of analysis. We went on to 

discuss the apparent connectivity 

between wolverines in the contiguous 

United States and Canada, and we 

considered the contiguous United States 

to be genetically continuous with 

wolverines in adjacent Canadian 

provinces. We concluded that a small 

effective population size would be more 

of a concern if the population was in 

isolation; however, wolverines in the 

contiguous United States are not 

genetically isolated from wolverines in 

Canada. 

Our 2023 Response: The best 

available estimate of effective 

population size for the wolverine in the 

Northern Rocky Mountains continues to 

be 35 (credible interval = 28–52) 

(Schwartz et al. 2009, p. 3226). We 

estimated the effective population size 

of wolverines in the North Cascades to 

be four (Service 2023, p. 27). Overall, 

the effective population size estimates 

of wolverines in the contiguous United 

States are small compared to 

conservation guidelines, and the 

contiguous U.S. DPS of North American 

wolverines appear to be vulnerable to 

inbreeding and loss of genetic diversity 

when considered in isolation. However, 

only one or two effective migrants per 

generation (i.e., the number of migrants 

that reproduce at the same rate as 

residents) are likely needed to achieve 

genetic population connectivity and 

maintain existing levels of genetic 

diversity (Cegelski et al. 2006, p. 209). 

At the time we published the October 

13, 2020, withdrawal document (85 FR 

64618), we considered the contiguous 

U.S. population to be genetically 

continuous with Canada. We now know 

that wolverine populations in southern 

British Columbia and Alberta near the 

transboundary interface are less 

genetically connected to the contiguous 

United States than we found in our 2018 

SSA. New information has revealed that 

female wolverines appear to avoid 

crossing major roadways, including the 

Trans-Canada Highway (Highway 1) and 

the Crowsnest Highway (Highway 3) in 

southern British Columbia (Sawaya et 

al. 2023, pp. 11–14). Substantially lower 

mitochondrial DNA diversity in the 

United States, as compared to 

mitochondrial DNA diversity in Canada, 

is consistent with the nuclear DNA 

signals of limited contemporary female 

gene flow between the countries and the 

wolverine’s relatively recent 

recolonization at the southern edge of 

their range (Sawaya et al. 2023, p. 17). 

See ‘‘Gene Flow Between the United 

States and Canada’’ and ‘‘Population 

Structure and Gene Flow Within 

Canada,’’ below, for more detail. Given 

the new information on limited gene 

flow with Canada and the potential 

impacts of climate change to future 

dispersal, the low effective population 

size in the contiguous U.S. population 

of North American wolverines is a 

concern to future population viability. 

(3) Comment: We received several 

public comments during our request for 

information claiming that the North 

American wolverine faces threats from 

indiscriminate trapping in the 

contiguous United States, or are 

negatively impacted by incidental 

trapping. 

Our 2020 Response Summarized: In 

our October 13, 2020, withdrawal 

document (85 FR 64618), we stated that 

trapping or hunting of wolverines was 

not allowed in any State within the 

range of the wolverine in the contiguous 

United States, and we presented the 

legal protections afforded to wolverines 

in each State. We summarized what we 

knew at the time about incidental 

trapping. In the wolverine SSA report, 

we provided a summary of the number 

of wolverines that have been 

incidentally trapped in Idaho (18 since 

1965, including 6 known to be released 

alive and 7 known mortalities), Montana 

(4 since 2013, 3 mortalities and 1 

released unharmed), and Wyoming (2 

since 1996, 1 mortality and 1 released 

unharmed) (Service 2018, p. 66). Both 

Idaho and Montana are implementing 

trapper education programs to minimize 

nontarget wolverine captures. We noted 

that regulated trapping and hunting of 

wolverines occurs in parts of Alaska and 

Canada, and appears to be sustainable 

based on population and density 

estimates. 

Our 2023 Response: Legal trapping of 

wolverines has not occurred in the 

contiguous United States in the past 10 

years. Wolverine trapping remains 

closed throughout the western United 

States, and wolverines have retained 

various protected status designations in 

the States within their current U.S. 

range (Service 2023, table 10). 

Therefore, legal direct trapping is no 

longer a stressor on wolverines in the 

contiguous United States. In the past 10 

years, lethal incidental trapping of 

wolverines has been minimal 

(approximately 1 to 2 animals per year 

or fewer), primarily occurring in Idaho 

and Montana (see Overutilization for 

Commercial, Recreational, Scientific, or 

Educational Purposes, below). New 

information suggests that recent 

overharvest from trapping has occurred 

in southern Canada in areas that could 

provide dispersing individuals to the 

contiguous United States (Mowat et al. 

2020, entire). Trapping in southern 

Canada appears to have had a more 

negative effect on wolverine 

populations in Canada than previously 

thought. Legacy effects of recent 

unsustainable trapping levels in a 

portion of the southern Rocky 

Mountains of Canada could limit 

dispersal of individuals into the 

contiguous United States in an area 

where wolverine connectivity between 

the United States and southern Canada 

is vital to the genetic and demographic 

health of the U.S. wolverine population. 

See Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes and Provisions of the Interim 

4(d) Rule, below, for further details. 


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(4) Comment: We received several 

public comments identifying potential 

threats to wolverines from winter 

recreation activities, such as 

snowmobiling and backcountry skiing. 

Our 2020 Response Summarized: 

When we published our October 13, 

2020, withdrawal document (85 FR 

64618), there was little information on 

the effect of winter recreation on 

wolverines. We received a final report of 

a multiyear study on the effects of 

winter recreation on wolverines 

(Heinemeyer et al. 2017, entire) in midDecember 2017, and the results of this 

study were published (Heinemeyer et al. 

2019a, entire) prior to the publication of 

our 2020 withdrawal document. The 

study found that wolverines were 

displaced from habitat by winter 

recreation but maintained multiyear 

home ranges, and the authors suggest 

that wolverines are able to tolerate 

winter recreation at some scales 

(Heinemeyer et al. 2017, p. iv; 

Heinemeyer et al. 2019a, p. 16). The 

study described habitat selection as 

complex for female wolverines and 

stated that habitat selection was likely 

driven by a combination of abiotic 

(snow, cold) and biotic (predator 

avoidance, food availability) factors 

(Heinemeyer et al. 2017, p. 36; 

Heinemeyer et al. 2019a, p. 16). This 

study did not assess demographic 

effects, fitness effects, or populationlevel effects of winter recreation on 

wolverines (Heinemeyer et al. 2019a, 

pp. 17, 19). 

Our 2023 Response: There are 

multiple recent studies that indicate 

wolverines are negatively affected and 

displaced (at least temporarily) by 

various types of backcountry winter 

recreation (Barrueto et al. 2022, entire; 

Heinemeyer et al. 2019a, entire; 

Heinemeyer et al. 2019b, entire; Kortello 

et al. 2019, entire; Mack and Hagen 

2022, entire; Regan et al. 2020, entire). 

The effect of winter recreation activity 

(of concern due to potential impacts to 

denning and survival), in isolation, 

represents a low threat to wolverines in 

the contiguous United States at the 

population level. However, in 

combination with other threats, 

including decreased snow availability 

(see Climate Change, below) and 

increased overlap with winter 

recreationalists in the future due to 

climate change, winter recreation could 

negatively affect wolverine population 

resilience in the future. See Disturbance 

Due to Winter Recreational Activity, 

below, for further details. 

(5) Comment: We received public 

comments claiming that wolverines are 

dependent on deep snow for survival 

and expressing concern for future 

changes in snowpack due to the effects 

of climate change. 

Our 2020 Response Summarized: Our 

response to this comment in our 

October 13, 2020, withdrawal document 

(85 FR 64618) focused on snow 

availability for denning and the 

wolverine’s ability to cope with 

changing snow conditions in the 

denning context. We stated that 

wolverines can and have denned 

outside of heavy snowpack, multiple 

factors play a role in den site selection, 

females will move dens as young 

become mobile, and areas of significant 

snowpack will likely persist in the 

future the contiguous United States in 

areas where wolverines are known to 

den at levels that will continue to 

support wolverines. Our review of 

studies of wolverine denning activity 

found no quantitative data reporting 

snow depth at the den site when 

wolverines abandon the den. More 

importantly, wolverine reproductive 

success has not been studied relative to 

a number of abiotic and biotic 

conditions, including depth and 

temporal aspect of spring snow cover. 

In our evaluation of the effects of 

climate change to snowpack (see Service 

2018, pp. 73–99), we presented a finerscale analysis (0.0625 km2 (0.24 mi2)) 

for two study areas (Glacier National 

Park and Rocky Mountain National 

Park) that focused directly on May 15, 

in addition to the presence or absence 

of snow on May 1 and April 15. These 

dates are more relevant to the North 

America wolverine’s life-history needs. 

We also modeled the depth of 

‘‘significant’’ snow (0.5 m (20 in)) on 

these dates. We found that large areas 

(several hundred km2/mi2 for each 

study area) of future snow cover (greater 

than 0.5 m (20 in) in depth) are 

projected to persist on May 1 at 

elevations currently used by wolverines 

for denning. This is true, on average, 

across the range of climate models used 

out to approximately year 2055. 

Our 2023 Response: As discussed 

above in our response to (1) Comment, 

the wolverine is a snow-adapted species 

that utilizes cold and snowy habitats for 

multiple aspects of its life history. To 

inform our assessment of the 

wolverine’s status in the contiguous 

United States, we updated our previous 

climate change analysis, the details of 

which are summarized in the wolverine 

SSA report addendum (Service 2023, 

pp. 47–60). Our analysis focuses on the 

expected loss of snowpack out to 2100 

in five modeling domains that overlap 

with occupied and potential wolverine 

habitat in the contiguous United States 

across latitudinal, longitudinal, and 

elevation gradients. The Service chose a 

snow depth threshold of greater than or 

equal to 1 m (3.3 ft) to represent 

significant snow cover on May 1, which 

provides a more conservative estimate 

than was used in the 2018 SSA (i.e., 

greater than or equal to 0.5 m (20 in.) 

on May 1). This updated analysis shows 

that cold and snowy conditions at high 

elevations are expected to decrease, 

with spring snowpack at denning 

elevations decreasing as much as 50 

percent in some areas. As a result, we 

expect wolverine population resiliency 

in the contiguous United States to 

decrease in the future. For more 

information see Climate Change, below. 

(8) Comment: We also received public 

comments recommending that the North 

American wolverine not be listed as 

threatened or endangered under the Act. 

One commenter stated that State 

wildlife agencies are capable of 

managing the species and are able to 

provide protections that ensure 

continued population growth towards 

population objectives established by 

these agencies and that mandates of 

various Federal resource management 

agencies provide a commitment to 

managing wildlife habitat in a way that 

benefits all wildlife species, including 

wolverines and other forest carnivores. 

Our 2020 Response Summarized: We 

acknowledged that some members of the 

public supported our decision to 

withdraw our proposed rule to list the 

North American wolverine occurring in 

the contiguous United States as a 

threatened species under the Act. In the 

wolverine SSA report (Service 2018, 

appendix G), we provided a summary of 

the regulatory protections provided by 

western States and Federal agencies, as 

well as management measures being 

implemented, to conserve the wolverine 

and its habitat. Trapping or hunting of 

wolverines was prohibited in the 

contiguous United States when our 

October 13, 2020, withdrawal document 

(85 FR 64618) published. 

Our 2023 Response: We appreciate 

the regulatory protections and 

management measures our State wildlife 

agency partners and Federal resource 

management agencies have enacted to 

conserve the North American wolverine 

and its habitat (Service 2018, appendix 

G). However, we have determined that 

the contiguous U.S. DPS of North 

American wolverine meets the Act’s 

definition of a threatened species as 

described in this rule due to future 

threats, including the reduction in 

spring snowpack from climate change. 

This determination is not a reflection on 

the adequacy of State management or 

the capability of States to manage the 

species but rather an acknowledgement 

of the serious threat posed to the species 


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by climate change. Along with the 

listing, we are finalizing an interim 4(d) 

rule that will promote conservation of 

the contiguous U.S. DPS of North 

American wolverine by encouraging 

management of the landscape by our 

partners in ways that meet the 

conservation needs of the wolverine. 

The provisions of this 4(d) rule provide 

one of many tools we will use to 

promote the conservation of the 

contiguous U.S. DPS of North American 

wolverine. 

(10) Comment: We received 

comments from several organizations 

that support the listing of the North 

American wolverine and designation of 

critical habitat. Threats cited include 

restricted migration, habitat loss and 

connectivity related to threats from 

effects of climate change, nontarget 

trapping pressures, road mortality and 

other effects of roads (e.g., noise, 

pollution, fragmentation of habitat), 

motorized recreation and traffic in 

wildlife corridors, timber sales and 

associated roads, and effects of 

snowmobile traffic (habitat 

fragmentation and pollution, and 

change in behavior). 

Our 2020 Response Summarized: We 

found that demographic risks to the 

species from either known or most 

likely potential stressors (i.e., 

disturbance due to winter recreational 

activities, other human disturbances, 

effects of wildland fire, disease, 

predation, overutilization, genetic 

diversity, small population effects, 

climate change, and cumulative effects) 

were low based on our evaluation of the 

best available information at the time in 

relation to current and potential future 

conditions for the North American 

wolverine occurring in the contiguous 

United States and in the context of the 

attributes that affect the needs of the 

DPS (Service 2018, p. 103). Thus, we 

determined that the North American 

wolverine in the contiguous United 

States did not meet the definition of an 

endangered species or a threatened 

species under the Act. 

Our 2023 Response: Our 2018 

wolverine SSA report and 2023 SSA 

report addendum provide a thorough 

assessment of the threats affecting the 

North American wolverine in the 

contiguous United States. New 

information related to the threats 

affecting the contiguous U.S. DPS of the 

North American wolverine have led us 

to a different conclusion than the one 

we presented in our October 13, 2020, 

withdrawal document (85 FR 64618). In 

this final rule, we examine the best 

available information about threats to 

the wolverine, including effects from 

roads, disturbance due to winter 

recreational activity, other human 

disturbance, effects from wildland fire, 

disease, predation, overutilization 

(trapping), genetic diversity, small 

population effects, and climate change, 

including the cumulative effects of these 

threats. See Summary of Biological 

Status and Threats, below, for a 

complete discussion of threats affecting 

the DPS. After assessing the best 

available information, we conclude that 

the contiguous U.S. DPS of the North 

American wolverine is not currently in 

danger of extinction but is likely to 

become in danger of extinction within 

the foreseeable future throughout all of 

its range. 

(12) Comment: We received 

comments from several industry groups 

supporting our August 13, 2014, 

withdrawal (79 FR 47522) of our 

February 4, 2013, proposed rule (78 FR 

7864) to list the North American 

wolverine as threatened. In general, 

their support rests on the following: (1) 

The DPS determination presented in our 

previous proposed rules (both 2010 and 

2013) was flawed; (2) the North 

American wolverine does not meet the 

definition of a threatened species; (3) 

the obligate relationship with denning 

and need for snow has not been 

adequately addressed (and may be a 

habitat preference); and (4) climate 

model projections do not support 

complete loss of snow. They also urged 

us to reaffirm prior findings that winter 

recreation (motorized and 

nonmotorized) is not a threat to 

wolverines. 

Our 2020 Response Summarized: We 

reevaluated wolverines occurring in the 

contiguous United States under our 

Policy Regarding the Recognition of 

Distinct Vertebrate Population Segments 

Under the Endangered Species Act (DPS 

policy; 61 FR 4722, February 7, 1996). 

See Distinct Population Segment in the 

October 13, 2020, withdrawal document 

(85 FR 64618 at 64628–64631) for more 

information. We provided our analysis 

of the status of wolverines in the 

contiguous United States under 

Determination of Species Status in the 

October 13, 2020, withdrawal document 

(85 FR 64618 at 64645–64647). The 

topic of denning behavior is discussed 

in the wolverine SSA report (see ‘‘Use 

of Dens and Denning Behavior’’ under 

Reproduction and Growth in the 

wolverine SSA report (Service 2018, pp. 

23–28)). For our analysis of the effects 

of climate change to North American 

wolverines and denning habitat, see 

‘‘Climate Change and Potential for 

Cumulative Effects’’ in the October 13, 

2020, withdrawal document (85 FR 

64618 at 64642–64644). 

Our 2023 Response: In this final rule, 

we provide our revised evaluation of 

discreteness and significance under our 

DPS policy of the segment of the North 

American wolverine occurring in the 

contiguous United States considering 

new information available since the 

publication of our October 13, 2020, 

withdrawal document (85 FR 64618). 

We also explain how new information 

has led us to a different determination 

from previous DPS analyses. The 

analysis contained in this rulemaking 

supersedes and replaces any previous 

DPS analysis for the segment of the 

North American wolverine occurring in 

the contiguous United States. We 

conclude that the population of 

wolverines in the contiguous United 

States is discrete and significant in 

relation to the remainder of the species 

in North America. For more 

information, see Distinct Population 

Segment Analysis for Wolverine in the 

Contiguous United States, below. 

The wolverine population in the 

contiguous United States is expected to 

decrease in resiliency, redundancy, and 

representation in the foreseeable future. 

The best available information suggests 

that habitat loss as a result of climate 

change, and the resulting exacerbating 

effect on other stressors, are likely to 

decrease the viability of wolverines in 

the contiguous United States within this 

century (see ‘‘Summary of Future 

Condition’’ and Determination of North 

American Wolverine’s Status, below). 

Our review of the best scientific and 

commercial data available indicates that 

the contiguous U.S. DPS of the North 

American wolverine meets the Act’s 

definition of a threatened species. 

We acknowledge the precise causal 

mechanism(s) for the apparent 

association of wolverine distribution 

with persistent spring snow are not yet 

clear. The association could involve the 

importance of snow for denning or other 

aspects of the species’ biology and 

ecology. We address uncertainties under 

Areas of Uncertainty for Wolverine 

Habitat Needs, below. That said, we 

know that wolverines are a species that 

is adapted to, and has a strong 

preference for, cold and snowy 

conditions and that these conditions 

will be reduced in the future. The 

commenter is accurate in that climate 

models do not predict a complete loss 

of snow within the North American 

wolverine’s range in the contiguous 

United States. However, we expect 

climate change to reduce snowpack in 

areas used by wolverines by as much as 

50 percent in some places (see our 

analysis under Climate Change, below). 

We conclude increasing temperatures 

and decreasing snowpack have the 


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largest potential to influence the 

population viability of the contiguous 

U.S. DPS of the North American 

wolverine in the future. 

Regarding winter recreation, new 

information supports our understanding 

that some forms of winter recreation, 

backcountry motorized recreation 

especially, have the potential to 

negatively impact wolverines. See our 

response to (4) Comment, above, and 

Disturbance Due to Winter Recreational 

Activity, below, for further details. 

Comments From Tribes 

(14) Comment: We received 

comments from one consortium of 

Tribal nations stating that, based on the 

weight of evidence provided in our 

previous rules, the North American 

wolverine meets the Act’s definition of 

endangered or threatened and is 

therefore warranted for listing. Specific 

threats mentioned in the comment letter 

included current population status, 

winter recreation activities, and effects 

of climate change. The Tribes also 

included comments documenting the 

cultural value of the wolverine and 

connection to cultural practices and 

concern for the loss of wolverine 

populations in the contiguous United 

States. The Tribes encouraged the 

Service to use sound and solid science 

in the listing determination and noted 

that additional population monitoring 

and Tribal climate change modeling 

efforts are under way to evaluate the 

status of the wolverine. 

Our 2020 Response Summarized: We 

appreciate the unique perspective 

provided by the Tribal nations regarding 

the contribution of the North American 

wolverine to the Tribes’ culture and 

spirituality. We also appreciate the 

commitment of the Tribal nations to 

continue studies of wolverines. 

We used the best available scientific 

information to provide a detailed 

description of the North American 

wolverine’s life history and ecology, 

including a detailed discussion of 

wolverine denning habitat and behavior. 

We conducted an analysis to assess the 

current population status. Conservation 

measures and regulatory mechanisms 

relative to the North American 

wolverine were also provided in the 

wolverine SSA report. This information 

was used to evaluate the current and 

future conditions of the DPS. We 

evaluated results from a fine-scale 

analysis of the potential effects of 

climate change to future snowpack 

conditions and found significant areas 

of snow (several hundred km2/mi2) will 

persist on May 1 at elevations used by 

wolverines for denning. We determined 

that, based on the best available 

information, the North American 

wolverine in the contiguous United 

States did not warrant listing as 

threatened or endangered under the Act 

in 2020. 

Our 2023 Response: We appreciate 

the commitment of the Tribal nations to 

further our knowledge of this unique 

species. We have gathered the best 

available information on North 

American wolverines and used this 

information to assess the current and 

future population status of wolverines 

in the contiguous United States. 

Regarding winter recreation, see our 

response to (4) Comment, above, and 

Disturbance Due to Winter Recreational 

Activity, below, for further details. 

Regarding the effects of climate 

change to North American wolverines, 

see our response to (1) Comment, above, 

and Climate Change, below. We 

conclude that the contiguous U.S. DPS 

of the North American wolverine is not 

currently in danger of extinction but is 

likely to become in danger of extinction 

within the foreseeable future throughout 

all of its range. 

(15) Comment: We received 

comments from one Tribe whose 

territory is occupied by the North 

American wolverine. The Tribe 

submitted a comment letter in 2013 

supporting our proposed listing. The 

Tribe stated that the conservation and 

restoration of the wolverine and other 

species within this homeland is of great 

importance to the Tribe’s subsistence, 

culture, religion, and economy. The 

letter also identified conservation and 

management plans currently under 

development and highlighted that the 

wolverine is designated as a species of 

concern in these current draft plans. 

Specific comments were provided 

relative to threats from climate change 

(including relative to demographic 

stochasticity), recreation and urban 

development, and incidental take. 

Included in those comments were 

references to other studies under way 

(e.g., Adaptation Partners and climate 

change vulnerability assessments; 

winter recreation study) to evaluate 

these potential stressors. 

Our 2020 Response Summarized: We 

appreciate the perspective provided 

regarding the importance of the North 

American wolverine and other species 

to the Tribe and its commitment to 

current and future conservation and 

management actions. We also appreciate 

and evaluated the information presented 

in the citations that were provided in 

the comment letter. The best available 

scientific information was used to 

evaluate the current conditions (i.e., 

potential stressors, including winter 

recreation) and future conditions (e.g., 

effects of climate change) of the DPS. 

Based on the best available information, 

we determined that the North American 

wolverine in the contiguous United 

States did not warrant listing as 

endangered or threatened under the Act 

in 2020. 

Our 2023 Response: Information 

previously provided by the Tribe was 

considered in the 2018 SSA report. We 

include new and updated scientific 

information in the 2023 wolverine SSA 

report addendum, including 

information on the current conditions 

(i.e., potential stressors, including 

winter recreation) and future conditions 

(e.g., effects of climate change) of the 

DPS. Based on the best available 

information, we now determine that the 

contiguous U.S. DPS of the North 

American wolverine meets the Act’s 

definition of a threatened species. 

State Agency Comments 

In our October 13, 2020, withdrawal 

document (85 FR 64618), we also 

addressed the extensive comments from 

several western States, including 

previously submitted comments in 

response to the February 4, 2013, 

proposed listing rule (78 FR 7864) as 

well as additional comments submitted 

in response to our October 18, 2016, 

document that reopened the public 

comment period on the 2013 proposed 

listing rule (81 FR 71670). These 

comments were grouped together and 

summarized as described below. 

(16) Comment: We received detailed 

comments critical of our reliance on 

‘‘unverified’’ climate model projections 

in our February 4, 2013, proposed 

listing rule, the lack of discussion of 

assumptions in adopting the model 

findings, the lack of evaluating 

alternative hypotheses, and the need to 

evaluate these effects at the den-site 

scale. One State agency recommended 

that, given the disagreements in the 

scientific community on the 

interpretation of these results, the 

Service solicit an independent, 

scientific review of the February 4, 

2013, proposed listing rule. 

Our 2020 Response Summarized: In 

preparing the 2018 SSA report for the 

North American wolverine, our 

foundational science document for 

informing the October 13, 2020, 

withdrawal (85 FR 64618), we reviewed 

available reports and peer-reviewed 

literature, incorporated survey 

information for the purpose of preparing 

updated maps of the known current and 

historical occurrences of the North 

American wolverine, and contacted 

species experts to collect additional 

unpublished information. We evaluated 

the appropriate analytical tools to 


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address data gaps and uncertainties. In 

some instances, we used publications 

and other reports of the Eurasian 

subspecies (Gulo gulo gulo) to fully 

inform our knowledge of the North 

American wolverine (Gulo gulo luscus). 

Before finalizing the 2018 SSA report, 

the draft wolverine SSA report was 

submitted for peer review to four 

independent peer reviewers and 

submitted to our Federal, State, and 

Tribal partners for scientific review. We 

incorporated the results of these reviews 

in the 2018 wolverine SSA report, as 

appropriate. 

We recognized that climate trends and 

future (2055 and later) climate model 

projections indicated warming 

temperatures for much of western North 

America, and changes to snowpack 

conditions. Our assessment of climate 

change impacts indicated that large 

areas (several hundred km2/mi2 for each 

study area) of future snow (greater than 

0.5 m (20 in) in depth) would persist on 

May 1 at elevations currently used by 

wolverines for denning. This was true, 

on average, across the range of climate 

models used out to approximately year 

2055. 

Our 2023 Response: In the 2023 

wolverine SSA report addendum, we 

expanded upon our climate analysis 

from the 2018 SSA report. Both SSA 

documents went through an 

independent, scientific peer review 

process. The assessment of the climate 

modeling results, presented below 

under Climate Change, and applied in 

the ‘‘Summary of Future Condition’’ 

discussion, replaces and supersedes the 

analysis of modeling results presented 

in the February 4, 2013, proposed listing 

rule (78 FR 7864) and the October 13, 

2020, withdrawal document (85 FR 

64618). We acknowledge there are 

uncertainties around the nature of the 

wolverine’s relationship with cold and 

snowy conditions (see Areas of 

Uncertainty for Wolverine Habitat 

Needs, below). Cold and snowy 

conditions at high elevations favored by 

wolverines in the contiguous United 

States are expected to decrease, with 

spring snowpack at denning elevations 

decreasing as much as 50 percent in 

some areas. 

(17) Comment: We received 

comments critical of our previous 

support for findings by Schwartz et al. 

(2009) regarding effective population 

size. Relatedly, several States 

commented on recent dispersal/ 

movements of wolverines into 

California, Colorado, and Utah as 

evidence of population expansion. 

Our 2020 Response Summarized: In 

the October 13, 2020, withdrawal 

document (85 FR 64618), we referred to 

our response to (2) Comment for a 

discussion of effective population size 

(85 FR 64618 at 64620). Regarding 

recent occurrences of wolverines in the 

contiguous United States, we noted that 

wolverines had recently been found in 

areas where they were once extirpated 

in the contiguous United States. See 

‘‘Population Abundance and Density’’ 

in the October 13, 2020, withdrawal 

document (85 FR 64618 at 64634– 

64636) for more information. 

Our 2023 Response: The best 

available estimate of effective 

population size for the Northern Rocky 

Mountains continues to be that 

provided by Schwartz et al. 2009 (p. 

3226): 35 (credible interval = 28–52). 

We estimated the effective population 

size of wolverines in the North Cascades 

to be four (Service 2023, p. 27). We are 

not aware of any other estimates of the 

effective population size of North 

American wolverines in the contiguous 

United States. See also our response to 

(2) Comment, above, and Effective 

Population Size in the Contiguous 

United States, below, for more 

information. 

We have gathered updated occurrence 

information in our 2023 wolverine SSA 

report addendum (Service 2023, figure 

2). We acknowledge that there are recent 

occurrences of wolverines in the 

western United States in areas where 

they have not been reported for years or 

very rarely (California, Colorado, 

Oregon, and Utah). These occurrences 

outside of the known breeding 

distribution are encouraging, but there 

is no evidence of breeding population 

expansion into California, Colorado, 

Oregon, and Utah. 

(18) Comment: We received 

comments from several western States 

presenting clarifications or updates to 

incidental trapping events and trapping 

regulations. 

Our 2020 Response Summarized: We 

noted that trapping or hunting of 

wolverines was not allowed in any 

western State (with the exception of 

Alaska, which was not included in the 

DPS in our February 4, 2013, proposed 

listing rule (78 FR 7864)). Legal 

protections for wolverines are codified 

in western State laws and regulations 

concerning hunting and trapping. Since 

2013, there has been a zero quota for 

trapping or harvest of wolverines in 

Montana. We described the 

documentation of incidental trapping of 

wolverines in the contiguous United 

States (as recently as December 2017) 

and noted that not all events resulted in 

mortality. We acknowledged that both 

Idaho and Montana are implementing 

trapper education programs to minimize 

nontarget wolverine captures. 

Our 2023 Response: We gathered 

updated information from States within 

the North American wolverine’s range 

about incidental trapping, trapping 

regulations, and measures taken by 

States to prevent incidental trapping of 

wolverines. Lethal incidental trapping 

of wolverines has been minimal (1 to 2 

animals per year), primarily occurring 

in Idaho and Montana. In the 

Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes discussion, below, we provide 

an assessment of incidental trapping 

and the measures States are taking to 

reduce incidental trapping of 

wolverines. 

(19) Comment: Several States 

provided comments in response to our 

February 4, 2013, proposed listing rule 

(78 FR 7864) and our October 18, 2016, 

reopening of the public comment period 

(81 FR 71670) indicating their 

disagreement with our determination of 

a wolverine DPS for the contiguous 

United States. Specifically, some 

commenters stated that the criteria of 

significance should be reevaluated, 

noting that the February 4, 2013, 

proposed listing rule did not provide 

any substantive information to support 

our conclusion that the loss of the 

wolverine in the contiguous United 

States would result in a significant gap 

in the range of the species; that is, our 

previous use of the loss of latitudinal 

range does not provide a rational basis 

for concluding that the loss of the 

wolverine in the contiguous United 

States would be significant in relation to 

the taxon. Another commenter stated 

that the wolverine population in the 

contiguous United States is connected 

geographically and genetically to the 

Canada/Alaska populations and these 

northern populations were likely the 

source of recolonization during the 20th 

century. Further, this commenter stated 

there is not a difference in control of 

exploitation and conservation status 

between the United States and Canada. 

Another commenter noted that, 

throughout the February 4, 2013, 

proposed listing rule, the Service 

acknowledged that, historically, the 

wolverine population in the contiguous 

United States was markedly reduced by 

systematic predator control programs 

and unregulated trapping. The 

commenter pointed out that areas of 

suitable habitat in the North Cascades, 

where trapping has been minimal or 

nonexistent for decades, and northern 

Rockies were recolonized by animals 

from Canada, where relatively liberal 

trapping is still allowed. The 

commenter asserted that our 

characterization in the February 4, 2013, 

proposed listing rule of ‘‘liberal’’ 


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Canadian regulations as sufficient to 

‘‘maintain the robust conservation status 

of the Canadian population,’’ does not 

comport with our characterization that 

the very limited trapping in the 

contiguous United States (Montana 

only) is insufficient to maintain the 

rebounding population designated as a 

DPS. 

Our 2020 Response Summarized: In 

light of the updated analysis and new 

information included in the 2018 

wolverine SSA report, we reevaluated 

wolverines in the contiguous United 

States under our DPS policy. We 

concluded that the population of 

wolverines in the contiguous United 

States was not discrete in relation to the 

remainder of the species in North 

America. As a result, in 2020, the 

population of wolverines in the 

contiguous United States was not a 

listable entity under section 3(16) of the 

Act. See Distinct Population Segment in 

the October 13, 2020, withdrawal 

document (85 FR 64618 at 64627– 

64631) for more information. 

Our 2023 Response: As stated above, 

in this final rule we provide our revised 

evaluation of discreteness and 

significance under the DPS policy of the 

segment of the North American 

wolverine occurring in the contiguous 

United States considering new 

information. We also explain how new 

information has led us to different 

conclusions from previous DPS 

analyses. The analysis contained in this 

rulemaking supersedes and replaces any 

previous DPS analysis for the segment 

of the North American wolverine 

occurring in the contiguous United 

States. 

Regarding the commenter’s concern 

with the significance analysis, we have 

determined, as we did in the February 

4, 2013, proposed listing rule, that there 

is evidence that the loss of the 

wolverine in the contiguous United 

States would result in a significant gap 

in the range of the taxon. Based upon 

the loss of approximately 58,998,140 

acres (238,757 km2) of high-quality 

wolverine habitat from the southern 

extent of the range and the adaptive 

potential that part of the range provides 

against oncoming climate change 

impacts, and the 12-degree latitudinal 

gap in the wolverine’s range that would 

result if the U.S. population was lost, 

we determine that the loss of the 

contiguous U.S. wolverine population 

would result in a significant gap in the 

range of the taxon. Thus, the DPS meets 

the definition of significant in our DPS 

policy. For more information see 

Analysis of Significance, below. 

Regarding the commenter’s assertion 

that wolverines in the contiguous 

United States are connected to Canada, 

which relates to the discreteness 

analysis of our DPS policy, we do not 

consider wolverines in the contiguous 

United States to be genetically or 

morphologically discontinuous from 

wolverines in Canada (McKelvey et al. 

2014, entire; Pilgrim and Schwartz 

2018, entire; Sawaya et al. 2023, entire). 

Therefore, wolverines in the contiguous 

United States are not discrete based on 

marked separation from other 

populations of the same taxon. 

However, we determined that the 

wolverine meets the discreteness 

criterion in our DPS policy (61 FR 4722; 

February 7, 1996), as delimited by the 

international boundary with Canada and 

given differences in control of 

exploitation, conservation status, and 

regulatory mechanisms that are 

significant in light of section 4(a)(1)(D) 

of the Act. See Analysis of Discreteness, 

below, for more information. 

Finally, regarding the commenter’s 

point about our characterization in the 

February 4, 2013, proposed listing rule 

of trapping in Canada versus the 

contiguous United States, we have 

considered updated trapping 

information in our DPS analysis. New 

information available since the 

publication of our October 13, 2020, 

withdrawal document (85 FR 64618) 

indicates that overharvest from trapping 

in Canada was likely causing more of an 

impact than previously thought. Recent 

studies show that harvest levels in 

portions of southeastern British 

Columbia and southwestern Alberta 

were unsustainable and causing 

population declines (Mowat et al. 2020, 

entire; Barrueto et al. 2022, entire) and 

could negatively impact movement of 

individuals from Canada to the 

contiguous United States (Sawaya 2023, 

pers. comm.). We now conclude that the 

differences between Canada and the 

United States in control of exploitation 

are significant in light of section 

4(a)(1)(D) of the Act and the wolverine 

population in the contiguous United 

States meets the DPS policy’s standard 

for ‘‘discreteness.’’ See Analysis of 

Discreteness, below, for more 

information. 

We conclude that the population of 

wolverines in the contiguous United 

States is discrete and significant in 

relation to the remainder of the species 

in North America. For our complete 

DPS analysis, see Distinct Population 

Segment Analysis for Wolverine in the 

Contiguous United States, below. 

Comments Received in Response to Our 

November 23, 2022, Publication 

As stated above, on November 23, 

2022, we published a document in the 

Federal Register (87 FR 71557) 

soliciting new information to update the 

wolverine SSA so that we could 

reevaluate whether the North American 

wolverine occurring in the contiguous 

United States is a distinct population 

segment and, if so, whether the distinct 

population segment meets the definition 

of an endangered or threatened species 

under the Act. This document also 

notified the public that the February 4, 

2013, proposed listing rule (78 FR 7864) 

had been reinstated as a result of court 

action. In response to the November 23, 

2022, publication, we received 

additional information including survey 

results, reports, documented mortalities, 

management efforts, and recent 

wolverine literature that we evaluated 

and incorporated as appropriate into our 

wolverine SSA report addendum. 

Although not requested, we also 

received comments from submitters on 

topics related to determinations 

regarding wolverine, including whether 

the wolverine should or should not be 

listed as an endangered or threatened 

species under the Act. The comments 

we received are similar to those we 

present and respond to above. 

Peer Reviewer Comments on the 2023 

Wolverine SSA Report Addendum 

We received comments from three 

peer reviewers on the draft wolverine 

SSA report addendum. We reviewed all 

comments we received from the peer 

reviewers for substantive issues 

regarding the information contained in 

the wolverine SSA report addendum, as 

well as any new information. The peer 

reviewers generally provided additional 

references, clarifications, and 

suggestions, including further 

definitions of some of the terms used in 

the wolverine SSA report addendum. 

We updated the wolverine SSA report 

addendum based on the peer reviewers’ 

comments, including revising some of 

our adaptive capacity scores, clarifying 

specific points where appropriate, and 

adding additional details and suggested 

references where needed. Peer reviewer 

comments are addressed in the 

following summary. 

(PR1) Comment: Regarding our 

climate change analysis, one peer 

reviewer did not agree with our initial 

characterization of the shared 

socioeconomic pathway (SSP) 5–8.5 

emissions scenario as worst case, and 

stated there are possible scenarios that 

could be more extreme. They also 

recommended the wolverine SSA report 

addendum more clearly point out the 

uncertainty around the climate models 

and emissions scenarios by stating the 

scenarios are representative of a large 


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portion of plausible outcomes, but not 

all. 

Our Response: We addressed the peer 

reviewer’s concern by removing 

mention of likelihood when discussing 

specific emissions scenarios. We also 

modified the text to include the latest 

guidance from the White House Office 

of Science and Technology Policy on 

Selecting Climate Information to Use in 

Climate Risk and Impact Assessments 

(OSTP 2023, entire), which recommends 

using SSP5–8.5 as an upper bounding 

scenario. We applied SSP5–8.5 as the 

upper bound to estimate future snow 

cover available for wolverines within 

the selected domains. 

(PR2) Comment: A peer reviewer 

questioned why we used the SSP2–4.5 

and SSP5–8.5 emissions scenarios for 

our future condition analysis. They 

suggested we use SSP1–1.9 instead of 

SSP2–4.5 since it is the opposite 

extreme of SSP5–8.5. 

Our Response: For our future analysis, 

we used SSP2–4.5 because that 

emissions scenario is closest to the 

current emissions trajectory we are on 

now, which provides a plausible lower 

boundary estimate of future snow cover 

available for North American 

wolverines. The Intergovernmental 

Panel on Climate Change (IPCC) has 

recently deemed our ability to limit 

warming to 1.5 °C (2.7 °F) (SSP1–1.9) as 

‘‘impossible’’ with no or limited 

overshoot in its 2022 gap analysis (Riahi 

et al. 2022, p. 298). Scenario SSP5–8.5 

reflects a no-emissions mitigation 

policy, which provides a plausible 

upper boundary estimate of available 

future snow cover. 

(PR3) Comment: A peer reviewer was 

concerned that the wolverine SSA 

report addendum did not list snow as an 

important attribute when studies have 

shown dens are concordant with spring 

snow coverage. The peer reviewer 

disagreed with our reasoning for 

excluding snow, which was because we 

do not know how it impacts survival 

and reproduction, and stated we should 

also remove food habits, physical 

features, and home range size since it is 

not clear how any of these impact 

survival and reproduction. They believe 

the case for snow is much stronger than 

any of these other factors. 

Our Response: We considered the 

information provided and addressed the 

peer reviewer’s concern by updating the 

wolverine SSA report addendum to 

include snow as an important attribute 

of wolverine habitat. 

(PR4) Comment: One peer reviewer 

was concerned about the use of spring 

snow cover for distribution. They 

questioned our use of the term 

‘‘persistent spring snow’’ and the May 

15 end date that is often associated with 

the term. The peer reviewer 

recommended analyzing snow cover 

between February and March, when 

young are newborn and most in need of 

thermal cover in natal dens. The 

reviewer believed that any analysis of 

climate change effects at those more 

critical times for denning would not 

likely show impacts. 

Our Response: We used the term 

‘‘persistent spring snow’’ in the 

wolverine SSA report addendum 

because it is a term frequently used in 

the scientific literature for wolverines 

and appears to be correlated to the 

wolverine’s circumpolar distribution. 

Snow model outputs for May 1 are 

presented in the 2023 wolverine SSA 

report addendum. May 1 was used 

based on previous studies documented 

in the 2018 SSA (Service 2018, p. 26), 

indicating wolverine den site 

abandonment generally occurs before 

May 1. We acknowledge that young kits 

are in natal dens usually from midFebruary to mid-March, so the use of 

May 1 snow projections is a 

conservative approach, but one which is 

consistent with the literature. 

As described in the wolverine SSA 

report addendum, there are a number of 

hypotheses for why wolverines prefer 

cold and snowy habitats, and not all of 

them are limited to denning (i.e., easier 

to get food, more food caching sites, 

etc.). These things could be important 

for adults throughout the breeding cycle 

or for juveniles as they become more 

independent from their mothers. We 

also discuss the possibility of other 

factors that are correlated to persistent 

spring snow, such as low temperatures 

(also analyzed in Copeland et al. 2010, 

entire), being the causal mechanisms for 

the observed relationship. In the 

wolverine SSA report addendum, we 

acknowledge wolverines have been 

documented denning in areas without 

persistent spring snow (Aronsson and 

Persson 2017, p. 266; Copeland et al. 

2010, pp. 240–242; Fisher et al. 2022, p. 

8; Jokinen et al. 2019, pp. 6–8; Persson 

et al. 2023, entire; Webb et al. 2016, pp. 

1466–1467); however, this phenomenon 

appears to be associated with cold, highlatitude boreal or arctic forests rather 

than the alpine habitats used by 

wolverines in the contiguous United 

States. In the contiguous United States, 

there is no evidence that wolverines 

have denned in areas without persistent 

spring snow. 

(PR5) Comment: One peer reviewer 

recommended including potential ways 

wolverines could adapt their denning 

behavior or use smaller or shallower 

patches of snow for denning in response 

to effects from climate change. 

Our Response: We added language to 

the wolverine SSA report addendum to 

address this comment and we also 

included additional text that snow may 

be important for more than just denning. 

As stated above, there is no evidence 

that wolverines have denned in areas 

without persistent spring snow in the 

contiguous United States. 

(PR6) Comment: A peer reviewer 

pointed out that future recreation will 

not just increase due to an increase in 

the human population, but also because 

snow-dependent recreational activities 

will be constrained to a smaller area that 

still contains quality snow in the future. 

Our Response: We included text in 

the wolverine SSA report addendum 

reflecting the reviewer’s comment. 

(PR7) Comment: One peer reviewer 

suggested adding Colorado’s wolverine 

reintroduction plan to the wolverine 

SSA report addendum as a voluntary 

conservation measure. 

Our Response: We updated the 

wolverine SSA report addendum to 

include a description of Colorado Parks 

and Wildlife’s previous consideration of 

reintroducing wolverines to Colorado as 

a nonessential experimental population 

(see 78 FR 7890, February 4, 2013). We 

also describe how this proposal was 

subsequently withdrawn in 2014 (see 79 

FR 47522, August 13, 2014), when we 

withdrew the February 4, 2013, 

proposed listing rule (78 FR 7864), and 

that there is currently no formal 

proposal to reintroduce wolverines to 

Colorado. 

(PR8) Comment: Two peer reviewers 

provided additional documentation 

regarding roads acting as a barrier to 

wolverine dispersal. Both provided 

different situations where at least one 

wolverine was seen crossing roadways, 

including a multiple-lane highway. One 

peer reviewer also mentioned regularly 

seeing wolverine tracks crossing 

roadways. 

Our Response: We updated the 

wolverine SSA report addendum to 

reflect these observations and modified 

the text to clarify that highways can 

limit female gene flow in some 

situations, but they are not complete 

barriers to wolverine movements. 

(PR9) Comment: One peer reviewer 

questioned how the artificial cutoff of 

the U.S.-Canada international border 

influenced the results of the 2009 

effective population size analysis 

(Schwartz et al. 2009, entire). 

Our Response: The effective 

population size estimate was only for 

the U.S. portion of the Northern 

Rockies, and there were no samples 

taken from Canada. As we stated in the 

wolverine SSA report addendum, 

connectivity to larger source 


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populations can alleviate the adverse 

effects of small effective population 

sizes (Frankham et al. 2014, entire). We 

also added a paragraph to the wolverine 

SSA report addendum to explain that 

because effective population size 

estimates for wolverine are small, 

connectivity with populations in 

Canada to allow for migration and gene 

flow is crucial to maintaining genetic 

diversity. 

(PR10) Comment: One peer reviewer 

was concerned that current data for the 

wolverine are not being compared to 

what is known historically. They 

specifically called out the comparison of 

population sizes, the distribution and 

abundance of wolverines in the 

contiguous United States, and the 

results of genetic studies. 

Our Response: As the peer reviewer 

mentioned, there is a lack of historical 

data to compare to current conditions. 

However, our assessment is a forwardlooking one, based on current and future 

conditions, and not the change from 

historical conditions to current 

conditions. 

(PR11) Comment: One peer reviewer 

questioned the 40 percent decline in 

wolverine abundance within a national 

park complex in southwestern Canada 

(Mowat et al. 2020, entire; Barrueto et 

al. 2022, entire). 

Our Response: The Barrueto et al. 

(2022) effort is a decade-long research 

project that was peer reviewed and 

published in a scientific journal. We 

note that the initial population estimate 

was approximately 50 wolverines at the 

start of the study, so a 40 percent 

decline over 10 years results in the loss 

of approximately 15–20 wolverines. The 

wolverine SSA report addendum has 

been updated to provide this additional 

detail. 

(PR12) Comment: A peer reviewer 

suggested including additional detail on 

how species-specific trapping and 

snaring reduce the likelihood of 

incidentally capturing a wolverine. 

Our Response: We updated the 

wolverine SSA report addendum to 

include how trappers use pan tension, 

site selection, and snare height to 

reduce the likelihood of incidental 

capture. We also included additional 

information we received from the States 

on their efforts to reduce incidental 

trapping of wolverines. 

(PR13) Comment: One peer reviewer 

suggested that the median and quartiles 

presented in our modeling may not 

accurately capture the variability in 

environmental conditions. The reviewer 

suggested that in addition to calculating 

the lower-quartile, median, and upperquartile at each individual grid cell and 

timestep, we should also calculate the 

maximum and minimum bracketing 

response. 

Our Response: We did not conduct 

the additional suggested analysis. The 

additional analysis would require 

significant work and time, and we 

conclude our approach includes the 

majority of plausible future outcomes 

and incorporates the best available 

information to inform our listing 

determination. 

I. Final Listing Determination 

Background 

A comprehensive review of the life 

history, population trends, and ecology 

of the North American wolverine is 

presented in the wolverine SSA report 

(Service 2018, pp. 3–44) and wolverine 

SSA report addendum (Service 2023, 

entire). The Service recognizes the 

North American wolverine as the 

subspecies Gulo gulo luscus (Service 

2018, p. 8). Wolverines are a mediumsized (about 1 m (3.3 feet (ft)) in length) 

carnivore, with a large head, broad 

forehead, and short neck (Service 2018, 

p. 4). Wolverines have heavy 

musculature and relatively short legs, 

and large feet with strong, curved claws 

for digging and climbing (Service 2018, 

p. 4). Their feet are adapted for travel 

through deep snow and, during the 

winter, dense, stiff, bristle-type hairs are 

found between the toes and around the 

foot pad. This characteristic becomes 

diminished in the summer (Service 

2018, p. 4). The wolverine is the largest 

terrestrial member of the Mustelidae 

family, which includes weasel, fisher, 

mink, marten, and others, and resembles 

a small bear with a bushy tail (Service 

2018, p. 1). Wolverines possess a 

number of morphological and 

physiological adaptations that allow 

them to travel long distances, and they 

maintain large territories in remote areas 

(Service 2018, p. 1). They have been 

described as curious, intelligent, and 

playful but cautious animals, though 

their social behavior and social 

organization has not been well-studied 

(Service 2018, p. 1). In North America, 

wolverines are found in Alaska, much of 

Canada, and the western-northwestern 

United States. 

During the late 1800s and early 1900s, 

the wolverine population declined or 

was extirpated in much of the 

contiguous United States (lower 48 

States), which was most likely the result 

of unregulated trapping and predator 

poisoning campaigns. Following 

regulation of trapping and restrictions 

on the use of poison, the wolverine 

population rebounded to some extent, 

and their distribution expanded to refill 

a portion of their previously extirpated 

range. In the contiguous United States, 

wolverines are known to reproduce in 

Washington, Idaho, Montana, and 

Wyoming (Service 2023, figure 3). 

Solitary individuals or lone dispersing 

individuals have been observed in other 

western States (Oregon, Colorado, Utah, 

and California), but there is no evidence 

of reproduction in the contiguous 

United States outside of the Northern 

Rocky Mountains in Idaho, Montana, 

and Wyoming and the Cascade 

Mountains of Washington. 

Regulatory and Analytical Framework 

Regulatory Framework 

Section 4 of the Act (16 U.S.C. 1533) 

and the implementing regulations in 

title 50 of the Code of Federal 

Regulations set forth the procedures for 

determining whether a species is an 

endangered species or a threatened 

species, issuing protective regulations 

for threatened species, and designating 

critical habitat for endangered and 

threatened species. In 2019, jointly with 

the National Marine Fisheries Service, 

the Service issued a final rule that 

revised the regulations in 50 CFR part 

424 regarding how we add, remove, and 

reclassify endangered and threatened 

species and the criteria for designating 

listed species’ critical habitat (84 FR 

45020; August 27, 2019). On the same 

day, the Service also issued final 

regulations that, for species listed as 

threatened species after September 26, 

2019, eliminated the Service’s general 

protective regulations automatically 

applying to threatened species the 

prohibitions that section 9 of the Act 

applies to endangered species (84 FR 

44753; August 27, 2019). 

The Act defines an ‘‘endangered 

species’’ as a species that is in danger 

of extinction throughout all or a 

significant portion of its range, and a 

‘‘threatened species’’ as a species that is 

likely to become an endangered species 

within the foreseeable future throughout 

all or a significant portion of its range. 

The Act requires that we determine 

whether any species is an endangered 

species or a threatened species because 

of any of the following factors: 

(A) The present or threatened 

destruction, modification, or 

curtailment of its habitat or range; 

(B) Overutilization for commercial, 

recreational, scientific, or educational 

purposes; 

(C) Disease or predation; 

(D) The inadequacy of existing 

regulatory mechanisms; or 

(E) Other natural or manmade factors 

affecting its continued existence. 

These factors represent broad 

categories of natural or human-caused 


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actions or conditions that could have an 

effect on a species’ continued existence. 

In evaluating these actions and 

conditions, we look for those that may 

have a negative effect on individuals of 

the species, as well as other actions or 

conditions that may ameliorate any 

negative effects or may have positive 

effects. 

We use the term ‘‘threat’’ to refer in 

general to actions or conditions that are 

known to or are reasonably likely to 

negatively affect individuals of a 

species. The term ‘‘threat’’ includes 

actions or conditions that have a direct 

impact on individuals (direct impacts), 

as well as those that affect individuals 

through alteration of their habitat or 

required resources (stressors). The term 

‘‘threat’’ may encompass—either 

together or separately—the source of the 

action or condition or the action or 

condition itself. 

However, the mere identification of 

any threat(s) does not necessarily mean 

that the species meets the statutory 

definition of an ‘‘endangered species’’ or 

a ‘‘threatened species.’’ In determining 

whether a species meets either 

definition, we must evaluate all 

identified threats by considering the 

species’ expected response and the 

effects of the threats—in light of those 

actions and conditions that will 

ameliorate the threats—on an 

individual, population, and species 

level. We evaluate each threat and its 

expected effects on the species, then 

analyze the cumulative effect of all of 

the threats on the species as a whole. 

We also consider the cumulative effect 

of the threats in light of those actions 

and conditions that will have positive 

effects on the species, such as any 

existing regulatory mechanisms or 

conservation efforts. The Secretary 

determines whether the species meets 

the definition of an ‘‘endangered 

species’’ or a ‘‘threatened species’’ only 

after conducting this cumulative 

analysis and describing the expected 

effect on the species now and in the 

foreseeable future. 

The Act does not define the term 

‘‘foreseeable future,’’ which appears in 

the statutory definition of ‘‘threatened 

species.’’ Our implementing regulations 

at 50 CFR 424.11(d) set forth a 

framework for evaluating the foreseeable 

future on a case-by-case basis. The term 

‘‘foreseeable future’’ extends only so far 

into the future as we can reasonably 

determine that both the future threats 

and the species’ responses to those 

threats are likely. In other words, the 

foreseeable future is the period of time 

in which we can make reliable 

predictions. ‘‘Reliable’’ does not mean 

‘‘certain’’; it means sufficient to provide 

a reasonable degree of confidence in the 

prediction. Thus, a prediction is reliable 

if it is reasonable to depend on it when 

making decisions. 

It is not always possible or necessary 

to define the foreseeable future as a 

particular number of years. Analysis of 

the foreseeable future uses the best 

scientific and commercial data available 

and should consider the timeframes 

applicable to the relevant threats and to 

the species’ likely responses to those 

threats in view of its life-history 

characteristics. Data that are typically 

relevant to assessing the species’ 

biological response include speciesspecific factors such as lifespan, 

reproductive rates or productivity, 

certain behaviors, and other 

demographic factors. 

Analytical Framework 

The wolverine SSA report and SSA 

report addendum document the results 

of our comprehensive biological review 

of the best scientific and commercial 

data regarding the status of the North 

American wolverine, including an 

assessment of the potential threats to the 

subspecies occurring in the contiguous 

United States. The wolverine SSA 

report and SSA report addendum do not 

represent our decision on whether the 

North American wolverine should be 

listed as an endangered or threatened 

species under the Act. However, they do 

provide the scientific basis that informs 

our regulatory decisions, which involve 

the further application of standards 

within the Act and its implementing 

regulations and policies. 

To assess viability of the North 

American wolverine occurring in the 

contiguous United States, we used the 

three conservation biology principles of 

resiliency, redundancy, and 

representation (Shaffer and Stein 2000, 

pp. 306–310). Briefly, resiliency is the 

ability of the species to withstand 

environmental and demographic 

stochasticity (for example, wet or dry, 

warm or cold years); redundancy is the 

ability of the species to withstand 

catastrophic events (for example, 

droughts, large pollution events), and 

representation is the ability of the 

species to adapt to both near-term and 

long-term changes in its physical and 

biological environment (for example, 

climate conditions, pathogen). In 

general, species viability will increase 

with increases in resiliency, 

redundancy, and representation (Smith 

et al. 2018, p. 306). Using these 

principles, we identified the subspecies’ 

ecological requirements for survival and 

reproduction at the individual, 

population, and species levels, and 

described the beneficial and risk factors 

influencing the subspecies’ viability. 

The SSA process can be categorized 

into three sequential stages. During the 

first stage, we evaluated the individual 

subspecies’ life-history needs. The next 

stage involved an assessment of the 

historical and current condition of the 

subspecies’ demographics and habitat 

characteristics, including an 

explanation of how the species arrived 

at its current condition. The final stage 

of the SSA involved making predictions 

about the subspecies’ responses to 

positive and negative environmental 

and anthropogenic influences. 

Throughout all of these stages, we used 

the best available information to 

characterize viability as the ability of a 

species (which, under the Act, includes 

any subspecies of fish or wildlife or 

plants, and any DPS of any species of 

vertebrate fish or wildlife which 

interbreeds when mature) to sustain 

populations in the wild over time. We 

use this information to inform our 

regulatory decision. 

Later in this document, we present a 

summary of the key results and 

conclusions from the 2018 wolverine 

SSA report and 2023 wolverine SSA 

report addendum; the full SSA report 

and SSA report addendum can be found 

at Docket No. FWS–R6–ES–2023–0216 

on https://www.regulations.gov and at 

https://ecos.fws.gov/ecp/species/5123. 

Distinct Population Segment 

Pursuant to the Act, 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 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 

(DPS policy; 61 FR 4722, February 7, 

1996). The DPS policy addresses the 

recognition of DPSs for potential listing 

actions. The DPS 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 Lists of Endangered and 

Threatened Wildlife and Plants (Lists), 

reclassification, and removal from the 

Lists. They are: (1) Discreteness of the 


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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, an endangered or threatened 

species). Discreteness refers to the 

degree of isolation of a population from 

other members of the species, and we 

evaluate this factor 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. 

When determining if a potential DPS is 

significant, our policy directs us to 

sparingly list DPSs while encouraging 

the conservation of genetic diversity. If 

we determine that a population segment 

is both discrete and significant, we then 

evaluate it for endangered or threatened 

species status based on the Act’s 

standards. 

We have conducted several DPS 

analyses of wolverines in the contiguous 

United States since 2010 in response to 

new information and legal challenges. 

We first found that the population 

qualified as a DPS in our 2010 12-month 

finding (75 FR 78030; December 14, 

2010) on a petition to list the population 

as a DPS. We reaffirmed and 

summarized this finding in our 

February 4, 2013, proposed listing rule 

(78 FR 7864). In 2020, we reversed our 

previous finding, based on information 

at the time which suggested the 

population was not discrete from 

wolverine populations in Canada (85 FR 

64618; October 13, 2020). Below, we 

provide our revised evaluation of 

discreteness and significance under the 

DPS policy of the segment of the North 

American wolverine occurring in the 

contiguous United States. Where 

necessary and appropriate below, we 

explain how new information has led us 

to different conclusions from previous 

DPS analyses. The analysis contained in 

this rulemaking supersedes and replaces 

any previous DPS analysis for the 

segment of the North American 

wolverine occurring in the contiguous 

United States. We determined that the 

contiguous U.S. population of the North 

American wolverine meets the 

discreteness criterion in our DPS policy; 

it is delimited by the international 

boundary with Canada, and there are 

differences between the United States 

and Canada regarding control of 

exploitation, conservation status, and 

regulatory mechanisms that are 

significant in light of section 4(a)(1)(D) 

of the Act. We then determined that the 

North American wolverine population 

occurring in the contiguous United 

States is significant because its loss 

would result in a significant gap in the 

range of the taxon. 

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 

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). 

Discreteness Based on Marked 

Separation 

In our February 4, 2013, proposed 

listing rule (78 FR 7864), we did not 

find marked separation from other 

populations to support discreteness of 

the contiguous U.S. wolverine 

population. We also did not find 

marked separation to support 

discreteness in our October 13, 2020, 

withdrawal (85 FR 64618). Our review 

of the new information presented in the 

2023 wolverine SSA report addendum 

has not altered that conclusion; we 

continue to find that there are no 

physical, physiological, ecological, or 

behavioral factors separating wolverines 

in the contiguous United States from 

wolverines in Canada. We do not 

consider wolverines in the contiguous 

United States to be genetically or 

morphologically discontinuous from 

wolverines in Canada based on genetic 

information that supports that Canadian 

wolverines repopulated the contiguous 

United States over the past several 

decades and there are no unique 

haplotypes in the contiguous U.S. 

population (McKelvey et al. 2014, 

entire; Pilgrim and Schwartz 2018, 

entire; Sawaya et al. 2023, entire). 

Therefore, wolverines in the contiguous 

United States are not discrete based on 

marked separation from other 

populations of the same taxon. 

We next evaluate whether the 

wolverine population in the contiguous 

United States is discrete based on the 

international boundary with Canada. 

We separately consider below whether 

there is discreteness based on 

differences between the two countries in 

terms of control of exploitation, 

management of habitat, conservation 

status, or regulatory mechanisms that 

are significant in light of section 

4(a)(1)(D) of the Act (inadequacy of 

existing regulatory mechanisms). 

Discreteness Based on the International 

Border—Differences in Control of 

Exploitation 

In our 2010 12-month finding (75 FR 

78030; December 14, 2010) and 2013 

proposed listing rule (78 FR 7864; 

February 4, 2013), we noted that 

differences in control of exploitation 

exist between the United States and 

Canada, but concluded those differences 

did not result in discreteness because 

the differences favored the contiguous 

U.S. population, the population that is 

at risk. In the wolverine 2018 SSA 

report, we noted that trapping or 

hunting of wolverines is currently 

prohibited in the contiguous United 

States and is allowed in Canada (Service 

2018, pp. 68–69). In that 2018 SSA 

report, we included an analysis of 

trapping efforts in southern Canada and 

trapping effort along the U.S.–Canada 

border, and based on that analysis, we 

found trapping to be limited. We again 

concluded in our October 13, 2020, 

withdrawal document (85 FR 64618) 

that the differences in exploitation were 

not significant in light of section 

4(a)(1)(D) of the Act (inadequacy of 

existing regulatory mechanisms). 

However, new information available 

since the publication of the October 13, 

2020, withdrawal document indicates 

that trapping in Canada was likely 

causing more of an impact than 

previously thought. Recent studies show 

that harvest levels in portions of 

southeastern British Columbia and 

southwestern Alberta were 

unsustainable and causing population 

declines (Mowat et al. 2020, entire; 

Barrueto et al. 2022, entire). The areas 

evaluated are close enough to the 

international border that dispersing 

individuals would be likely to provide 

important genetic diversity and 

demographic rescue to the population in 

the contiguous United States. Harvest 

levels in Canada could negatively 

impact movement of individuals from 

Canada because, with reduced 

populations in Canada, there is less 

pressure on individuals to move south 

to areas in the United States to find 

suitable vacant home ranges (Sawaya 


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2023, pers. comm.). Furthermore, female 

wolverines appear less likely to disperse 

long distances or across major roadways 

compared to males (Sawaya et al. 2019, 

pp. 621–23). According to the latest 

genetic analyses, virtually all of the 

recent movement of wolverines from 

Canada to the United States appears to 

be by males (Sawaya et al. 2023, pp. 12– 

14, 17). Although there is now a 

trapping moratorium in southeastern 

British Columbia (British Columbia 

2022, p. 76), it is unclear how long the 

moratorium will be in place or what the 

legacy effects of recent overharvest in 

southern British Columbia will be. In 

addition, trapping continues to be 

allowed in portions of southern Alberta. 

We conclude that harvest in Canada will 

continue to be an impediment to 

effective dispersal of wolverines into the 

United States. This, in turn, is likely to 

impact future genetic integrity of the 

population in the contiguous United 

States and limit the ability for 

demographic rescue should wolverines 

decline in number within the 

contiguous United States. Thus, we now 

conclude, based on new information, 

that the differences between Canada and 

the United States in control of 

exploitation are significant in light of 

section 4(a)(1)(D) of the Act. Existing 

regulations in Canada have been 

inadequate to address this exploitation. 

Alberta continues to allow trapping in 

areas important for potential dispersing 

wolverines, and there is uncertainty on 

the length and effectiveness of the 

trapping moratorium in British 

Columbia and the long-term population 

effects of the recent overharvest there. 

As a result, we conclude the wolverine 

population in the contiguous United 

States meets the standard of 

‘‘discreteness’’ and we use the 

international border between the United 

States and Canada to define the 

northern boundary of the contiguous 

U.S. wolverine discrete population. 

Discreteness Based on the International 

Border—Differences in Management of 

Habitat 

In the 2013 proposed listing rule (78 

FR 7864; February 4, 2013) and October 

13, 2020, withdrawal document (85 FR 

64618), we stated that management 

activities (e.g., timber harvest, wildland 

firefighting, prescribed fire, and 

silviculture) can modify wolverine 

habitat, but this species appears to be 

little affected by changes to the 

vegetative characteristics of its habitat. 

However, recent research in Canada 

indicates that wolverines and other 

carnivores can be displaced from habitat 

that is subject to human disturbance 

that includes harvest cut-blocks in 

forested habitat (Frey et al. 2020, entire). 

That said, most wolverine habitat in the 

contiguous United States occurs at high 

elevations in rugged terrain that is not 

usually conducive to intensive forms of 

silviculture and timber harvest. 

Although recent information indicates 

wolverines may be affected by 

disturbance from some types of habitat 

management, these disturbances occur 

in both the contiguous United States 

and southern Canada, where forested 

alpine habitats are managed in relatively 

similar ways and are relatively limited 

in scope and scale in wolverine habitat. 

Therefore, there are no significant 

differences in management of habitat 

between the United States and Canada 

pursuant to 4(a)(1)(D) of the Act. 

Discreteness Based on the International 

Border—Differences in Conservation 

Status 

In the December 14, 2010, 12-month 

finding (75 FR 78030), which is 

summarized in the February 4, 2013, 

proposed listing rule (78 FR 7864), we 

found that the wolverine population in 

the contiguous United States met the 

second DPS discreteness condition 

because of differences in conservation 

status as delimited by the U.S.-Canada 

international governmental boundary. 

We found that those differences were 

substantial and significant in light of 

section 4(a)(1)(D) of the Act. We stated 

that in the remaining current range in 

Canada and Alaska, wolverines exist in 

well-distributed, interconnected, large 

populations. We added that, conversely, 

wolverine populations in the remaining 

contiguous U.S. range appear to be at 

numbers so low that their continued 

existence could be at risk, especially in 

light of the threats to the subspecies. In 

the 2010 12-month finding, we stated 

that 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 patches 

separated by unsuitable habitat. As a 

result, we concluded that the 

contiguous U.S. population of the 

wolverine met the discreteness criterion 

in our DPS policy. Consequently, we 

used the international border between 

the United States and Canada to define 

the northern boundary of the contiguous 

U.S. DPS of the North American 

wolverine in our December 14, 2010, 12- 

month finding (75 FR 78030) and our 

February 4, 2013, proposed listing rule 

(78 FR 7864). 

In our October 13, 2020, withdrawal 

document (85 FR 64618), based on new 

information at the time, we concluded 

there were not significant differences in 

control of exploitation, conservation 

status, and management of habitat, nor 

other threats to the wolverine requiring 

regulatory mechanisms to address them, 

and we concluded that there are no 

differences in regulatory mechanisms 

between the United States and Canada 

that are significant in light of section 

4(a)(1)(D) of the Act. As a result, we 

concluded that the contiguous U.S. 

population of the North American 

wolverine did not meet the discreteness 

criterion in our DPS policy. Below, we 

revisit discreteness based on the 

international border and differences in 

conservation status considering new 

information presented in the wolverine 

SSA report addendum. 

Small Total Population Size— 

Wolverine population densities vary 

across North America and have been 

described as naturally low (van Zyll de 

Jong 1975, p. 434) given the species’ 

large home range, wide-ranging 

movements, and solitary characteristics 

(Service 2018, p. 56). There are far fewer 

wolverines in the contiguous United 

States (around 300) than there are in 

Canada (more than 15,000) and Alaska 

(likely in the thousands) (Committee on 

the Status of Endangered Wildlife in 

Canada (COSEWIC) 2014, pp. 36, 47; 

Inman et al. 2013, p. 282; Service 2018, 

p. 71), but this is largely a reflection of 

the amount of suitable habitat available 

within the contiguous United States 

(both currently and historically) for a 

species that needs large, exclusive 

territories. Even if wolverines occupied 

all available habitat in the contiguous 

United States, their populations would 

still be relatively small compared to 

Canada (i.e., the population capacity 

estimate was 644 (95% confidence 

interval (CI) = 506–1881) (Inman et al. 

2013, p. 282). A small population in the 

contiguous United States would be less 

of a conservation concern if there were 

greater connectivity with the larger 

populations in Canada. 

Recent genetic information indicates 

wolverines from Canada have slowly 

repopulated the contiguous United 

States over the past century since the 

era of unregulated predator removal 

(Service 2018, pp. 45–50; Sawaya 2023, 

pers. comm.). We stated in the 

December 14, 2010, 12-month finding 

(75 FR 78030) that differences in 

population sizes between the 

contiguous United States and Canada 

were reflective of a difference in 

conservation status. In our October 13, 

2020, withdrawal document (85 FR 

64618), based on new information, we 

concluded that the contiguous U.S. 

wolverines represent a peripheral 


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population at the southern extent of the 

North American wolverine’s range. 

Thus, we considered the small 

population size of wolverines in the 

United States to be a natural result of 

the limited habitat available and not 

reflective of a difference in conservation 

status. Our 2020 determination on this 

point was made with the understanding 

that there was sufficient connectivity 

with Canada such that dispersing 

wolverines could bolster the small 

population in the contiguous United 

States. However, new information on 

wolverine dispersal and genetic 

connectivity indicates that wolverines 

appear to be impacted by recent 

overharvest in Canada, barriers to 

female wolverine dispersal, and 

development in dispersal corridors 

between suitable habitat (Barrueto et al. 

2022, p. 4; Sawaya et al. 2023, pp. 12– 

14; Balkenhol et al. 2020, p. 799). 

Because of this, the small population in 

the contiguous United States is more at 

risk from future threats impacting 

population resiliency. We now conclude 

that the difference in population size on 

the contiguous U.S. side of the 

international border is a significant 

difference in conservation status in light 

of section 4(a)(1)(D) of the Act as it 

applies to discreteness. 

Effective Population Size—In our 

December 14, 2010, 12-month finding 

(75 FR 78030) and February 4, 2013, 

proposed listing rule (78 FR 7864), in 

support of our conclusion that 

differences in conservation status 

between the United States and Canada 

exist that are significant in light of 

section 4(a)(1)(D) of the Act, we 

discussed the difference in wolverine 

effective population size between the 

contiguous United States and Canada. 

The 2013 proposed listing rule 

presented an effective population size 

estimate for wolverines in the 

contiguous United States from a 

publication by Schwartz et al. (2009), 

which estimated a summed effective 

population size of 35, with credible 

limits from 28 to 52 (Schwartz et al. 

2009, p. 3,226). As provided in our SSA 

report (Service 2018, pp. 46–47), 

effective population sizes (Ne) are 

typically smaller than census 

population sizes. Ne is the number of 

individuals in a population that would 

result in the same loss of genetic 

diversity, inbreeding, and genetic drift, 

if they behaved in the manner of an 

idealized population (equal sex ratio, 

random mating, all adults producing 

offspring, equal numbers of offspring 

per parent, and a constant number of 

breeding individuals across generations) 

(Frankham 1995, p. 96). The concept of 

effective population size relates to 

population viability because, as a 

general rule, closed populations with 

random mating that have effective 

population sizes (1) below 50 are at 

higher risk of inbreeding depression, 

and (2) below 500 are more likely to lose 

genetic variation important to 

maintaining long-term evolutionary 

potential. In addition, small, isolated 

populations are more vulnerable to 

extinction through interactions between 

environmental, genetic, and 

demographic factors (Caughley 1994, 

pp. 221–227). Importantly, the concept 

and guidelines for genetically effective 

population size were developed for a 

single, isolated population (Laikre et al. 

2016, p. 280). Fragmentation can further 

exacerbate inbreeding depression and 

genetic loss, while connectivity to larger 

source populations can alleviate the 

adverse effects of small effective 

population sizes (Frankham et al. 2014, 

p. 60). 

In our October 13, 2020, withdrawal 

document (85 FR 64618), we 

acknowledged the low effective 

population size of wolverines in the 

contiguous United States but found this 

was not a concern given the evidence of 

genetic connectivity between the United 

States and Canada. We stated the 

currently known spatial distribution of 

genetic variability in wolverines in 

North America appeared to be a 

reflection of a complex history where 

population abundance has fluctuated 

since the time of the last glaciation and 

insufficient time has passed since 

human persecution for a full recovery of 

wolverine densities (Cardinal 2004, pp. 

23–24; Zigouris et al. 2012, p. 1,554). 

Zigouris et al. (2012, p. 1,545) posit that 

the irregular distribution of wolverines 

in the southwestern periphery and the 

genetic diversity observed in those 

analyses is a result of population 

bottlenecks that were caused by range 

contractions from a panmictic (random 

mating) northern core population 

approximately 150 years ago coinciding 

with human persecution. We stated that 

very few successful migrants are needed 

per generation to maintain at least 95 

percent of the genetic variation in the 

next 100 generations (approximately 

750 years) in the contiguous United 

States (Cegelski et al. 2006, p. 209). We 

concluded that this level of migration 

from the north had already been 

occurring following the end of intense 

predator removal campaigns that 

affected this subspecies. Given 

observations of wolverines moving vast 

distances over varied terrain and across 

the U.S.–Canada border, our assessment 

of the low levels of trapping mortality 

in Canada near the border, and further 

confirmation of Canada as the source of 

wolverine genetics present in 

contiguous U.S. wolverines, we believed 

that wolverines in the contiguous 

United States were not separated 

genetically from the larger population in 

Canada. In our October 13, 2020, 

withdrawal document (85 FR 64618), 

we concluded that wolverines in the 

contiguous United States exhibit genetic 

and phenotypic similarities with 

wolverines in Canada that implied 

connectivity with Canada. As such, we 

concluded in that withdrawal document 

that it was not biologically appropriate 

to consider the low effective population 

size of wolverines on the contiguous 

U.S. side of the border as a difference 

in conservation status that is significant 

in light of section 4(a)(1)(D) of the Act 

as it applies to discreteness. 

In our 2023 wolverine SSA report 

addendum, we summarized our 

evaluation of the available information 

related to the effective population size 

of wolverines in the contiguous United 

States, recent trapping/harvest in 

Canada, and genetic connectivity of 

wolverines between the United States 

and Canada. We are not aware of any 

new estimates of effective population 

size for wolverines in the contiguous 

United States; therefore, the Ne estimate 

of the wolverine population in the 

Northern Rocky Mountains (35) 

provided by Schwartz et al. (2009) 

represents the best available scientific 

information regarding effective 

population sizes in the U.S. portion of 

the Northern Rocky Mountains (Service 

2023, p. 27). In the 2023 wolverine SSA 

report addendum, we estimated the 

effective population size of the 

wolverine population in the North 

Cascade Mountains, resulting in an 

estimate of Ne = 4 (Service 2023, p. 27). 

When viewed in isolation, the overall 

effective population sizes for wolverines 

in the contiguous United States are 

under the conservation thresholds for 

short- and long-term genetic health (50 

and 500, respectively). New information 

suggests recent trapping harvest in 

southwestern Canada resulted in 

population declines in some areas that 

may be important sources of dispersing 

individuals to the contiguous United 

States (Service 2023, pp. 41–42). 

Furthermore, new information shows 

that female wolverine movement is 

influenced by major transportation 

corridors and that the Trans-Canada 

Highway could be an impediment to 

female movement (Service 2023, p. 28). 

Overall, the effective population size 

estimates of wolverines in the 

contiguous United States are small 


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compared to conservation rules-ofthumb and presumably smaller than the 

effective population size of wolverines 

in Canada. Only one or two migrants per 

generation are likely needed to achieve 

genetic population connectivity 

(Cegelski et al. 2006, p. 13); however, 

based on new information on gene flow 

and dispersal, we cannot assume this 

level of immigration from Canada is 

occurring. The contiguous U.S. 

population may be at risk of impacts 

from low effective population size 

without sufficient gene flow with 

Canada. We now conclude that the 

difference in effective population size 

on the U.S. side of the international 

border results in a significant difference 

in conservation status in light of section 

4(a)(1)(D) of the Act as it applies to 

discreteness. 

Habitat Fragmentation—In our 

December 14, 2010, 12-month finding 

(75 FR 78030) and February 4, 2013, 

proposed listing rule (78 FR 7864), we 

stated that wolverine habitat in the 

contiguous United States consists of 

small, isolated areas of high-elevation 

habitat separated from each other by 

low valleys of unsuitable habitat. We 

also described that these ‘habitat 

islands’ are represented by areas 

containing spring snow, citing Copeland 

et al. (2010). We concluded that the 

fragmented nature and distribution of 

wolverine habitat in the contiguous 

United States results in a population 

that is highly vulnerable to extirpation 

because of lack of connectivity between 

subpopulations, and this also makes 

them more vulnerable to external threats 

(75 FR 78030; December 14, 2010). This 

was used to support our justification for 

discreteness. 

The breeding range of wolverines in 

the contiguous United States largely 

exists in high-elevation alpine forested 

habitats. Those alpine areas with 

established wolverine home ranges are 

separated by expanses of lower 

elevation valley habitats that are not 

conducive to wolverine home range 

establishment but do provide varying 

levels of connectivity between home 

ranges or subpopulations. In Canada 

and Alaska, habitats are more 

contiguous and much less fragmented 

than wolverine habitat in the contiguous 

United States. The fragmented nature 

and distribution of wolverine habitat in 

the contiguous United States puts 

wolverines occurring in the contiguous 

United States at higher risk of impacts 

from climate change and other stressors 

compared to wolverines occurring in 

Canada and Alaska. We conclude that 

the difference in habitat fragmentation 

on the contiguous U.S. side of the 

international border results in a 

significant difference in conservation 

status in light of section 4(a)(1)(D) of the 

Act as it applies to discreteness. 

Discreteness Based on the International 

Border—Differences in Regulatory 

Mechanisms 

Wolverines are currently protected 

under various State regulatory 

designations in the States where the 

species occurs in the western United 

States (Service 2023, table 10). In 

Canada, provincial designations for the 

wolverine include endangered in 

Labrador, and threatened in Ontario and 

Que ́bec (‘‘threatened’’ is equivalent to 

endangered in Que ́bec), with the 

remaining provincial designations 

ranging from no ranking to sensitive or 

special concern to the Vancouver Island 

population’s designation as imperiled 

(COSEWIC 2014, p. 44). 

Current regulatory mechanisms 

prohibit trapping or harvest of 

wolverines in the contiguous United 

States, while trapping is legal in Canada 

and occurs in parts of the range that 

could be a source of important 

dispersers to the contiguous United 

States. We acknowledge that there is 

currently a trapping moratorium in a 

portion of British Columbia resulting 

from studies showing population 

declines in that area related to trapping 

(Service 2023, pp. 44–45). However, that 

moratorium is temporary and only 

covers a portion of the Canadian range 

(e.g., it does not include Alberta). As 

discussed above, there are significant 

differences in control of exploitation 

that may be impeding movement of 

wolverines, from Canada to the 

contiguous United States. We conclude 

that there are differences in regulatory 

mechanisms related to control of 

exploitation between the United States 

and Canada that are significant in light 

of section 4(a)(1)(D) of the Act. 

Discreteness Conclusion 

Based on our updated analysis 

described above and supported by 

information in the wolverine SSA report 

and the wolverine SSA report 

addendum, the contiguous U.S. 

population of the North American 

wolverine meets the discreteness 

criterion in our DPS policy (61 FR 4722; 

February 7, 1996). It is delimited by the 

international boundary with Canada, 

given differences in control of 

exploitation, conservation status, and 

regulatory mechanisms that are 

significant in light of section 4(a)(1)(D) 

of the Act. After determining that a 

vertebrate population is discrete, we are 

required to complete an analysis to 

determine if the population in question 

is significant according to our DPS 

policy; that analysis follows. 

Analysis of Significance 

If we determine a population segment 

is discrete, its biological and ecological 

significance will then be considered in 

light of Congressional guidance that the 

authority to list DPSs be used sparingly 

while encouraging the conservation of 

genetic diversity. In carrying out this 

examination, we consider available 

scientific evidence of the population’s 

importance to the taxon to which it 

belongs (i.e., the North American 

wolverine). Our DPS policy states that 

this consideration may include, but is 

not limited to: (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. Below, we address 

considerations 1, 2, and 4. 

Consideration 3 does not apply to the 

continental U.S. wolverine population 

because North American wolverines are 

distributed widely across Alaska and 

Canada. 

In our December 14, 2010, 12-month 

finding (75 FR 78030), we conducted an 

exhaustive analysis of the significance 

of the contiguous U.S. population of the 

North American wolverine; this analysis 

was incorporated by reference into our 

February 4, 2013, proposed listing rule 

(78 FR 7864). In the analysis, we 

concluded that the wolverine 

population in the contiguous United 

States is significant because its loss 

would result in a significant gap in the 

range of the taxon. In our October 13, 

2020, withdrawal document (85 FR 

64618), we did not present an 

assessment of significance under the 

DPS policy because, at that time, we 

determined that the wolverine 

population in the contiguous United 

States was not discrete, and thus there 

was no need to assess significance. 

Because we have now determined the 

wolverine population in the contiguous 

United States is discrete, we reviewed 

and present an update to our 2010 and 

2013 assessment of the significance of 

the wolverine population occurring in 

the contiguous United States using the 

best available information. 


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Unusual or Unique Ecological Setting 

Wolverines occupy a variety of 

habitats within North America, 

including Arctic tundra, subarcticalpine tundra, boreal forest, mixed 

forest, redwood forest, and coniferous 

forest (Banci 1994, p. 114). Wolverines 

in the contiguous United States exist in 

an ecosystem that includes highelevation, remote, rugged, alpine 

forested terrain and non-forested 

habitats around the tree line that retain 

snowpack into the spring. The 

ecoregions inhabited by wolverines in 

the contiguous United States are also 

present in large portions of their 

occupied range in Canada and Alaska 

(Service 2018, appendix A). 

Wolverines in the contiguous United 

States appear to use habitat attributes 

that are similar to wolverine 

populations in Canada and Alaska, 

where wolverines also use alpine 

habitats, and do not appear to exist in 

an unusual or unique ecological setting. 

Thus, we again do not rely on this factor 

when determining that the wolverine in 

the contiguous United States is 

significant to the taxon as a whole. 

Significant Gap in the Range of the 

Taxon 

Wolverines once lived throughout the 

North American Rocky Mountains from 

Alaska and Canada, south through 

Colorado and into New Mexico, and in 

the North Cascades of Washington and 

the Sierra Nevada Range of California. 

During the late 1800s and early 1900s, 

the wolverine population declined or 

was extirpated in much of the 

contiguous United States (Service 2018, 

p. 1). Wolverines have since recolonized 

parts of the contiguous United States, 

and the current breeding range includes 

the Southern Rocky Mountains of Idaho, 

Montana, and Wyoming and the 

Cascades of Washington (Service 2023, 

figure 3). Individual wolverines have 

been documented in California, 

Colorado, Oregon, and Utah; however, 

breeding populations are not known to 

exist in these areas. The contiguous 

United States represents the 

southernmost extent of the wolverine’s 

range in North America. 

Our significance determination in the 

December 14, 2010, 12-month finding 

(75 FR 78030) concluded that the loss of 

wolverines in the contiguous United 

States would result in a significant gap 

in the range of the taxon. This 

determination was based on an estimate 

of the historical range (not current 

range) of wolverine in the contiguous 

United States. This relied on a 

latitudinally-based interpretation of 

historical range in the contiguous 

United States, the majority of which was 

unoccupied at the time the estimation 

was made and remains unoccupied by 

wolverines. We stated in 2010 that the 

loss of the population in the contiguous 

United States would be significant 

because it would substantially curtail 

the range of the wolverine by moving 

the southern range terminus 

approximately 15 degrees latitude to the 

north (or approximately 40 percent of 

the presumed latitudinal extent of the 

wolverine’s range in North America). 

For reference, the U.S. border with 

Canada is 49 degrees North latitude. 

Fifteen degrees south of the border (at 

34 degrees North latitude), the assumed 

15-degree gap in latitude (49 degrees 

North minus 34 degrees North) 

presented in the DPS analysis in the 

December 14, 2010, 12-month finding 

(75 FR 78030), lands on 34 degrees 

North latitude, which runs through 

western States, including southern 

California and approximately the 

middle of Arizona and New Mexico, 

significantly south of the currently 

occupied range of wolverine in United 

States. 

During the development of our 2018 

wolverine SSA report and 2023 SSA 

report addendum, we conducted an 

extensive analysis of the recent and 

historical occurrence records for 

wolverines in the contiguous United 

States (Service 2018, pp. 12–16; Service 

2023, pp. 3–14). Our updated 

significance analysis is based on an 

updated, spatially explicit assessment of 

the current range of wolverines in the 

contiguous United States. We used the 

current range (Service 2023, figure 2) to 

provide a more accurate reflection of the 

range currently being used by 

populations of wolverines in the 

contiguous United States supported by 

the best available information. By 

focusing on the current range, and not 

the historical range, we avoid including 

large sections of the western United 

States that do not have high-quality 

wolverine habitat (southern California 

and northern Arizona and New Mexico) 

in our significance analysis, and thus 

we are able to better assess the 

significance of the population in the 

contiguous United States relative to the 

larger taxon. The current range of 

wolverines in the contiguous United 

States covers approximately 58,998,140 

acres (238,757 km2) of high-quality 

wolverine habitat with recent wolverine 

occurrences (from 2009–2023) (Service 

2023, figure 2), the loss of which would 

move the southern range terminus 

approximately 12 degrees latitude to the 

north. 

Furthermore, the southernmost 

portion of the range may be important 

for conservation, as it may allow for 

unique adaptive potential in the face of 

a changing global climate and future 

reduction in cold and snowy conditions. 

Populations on the periphery of species’ 

ranges tend to be given lower 

conservation priority because they are 

thought to exist in low-quality habitats 

and are also thought to be the 

populations that are least likely to 

survive a reduction in range (Wolf et al. 

1996, p. 1147). However, this tendency 

presumes that the ultimate cause of the 

species’ extinction will be one that 

operates by eroding away the species’ 

range beginning at the periphery and 

progressing to the center. This 

presumption is based on 

biogeographical information that habitat 

and population densities of species are 

highest near the center of the species’ 

range and decline near the edge (Brown 

and Lomolino 1998, figure 4.16). Data 

from documented range collapses of 

species from around the world, 

however, illustrate that species’ ranges 

tend to collapse to peripheral areas 

rather than to the center of their 

historical ranges (Lomolino and 

Channell 1995, p. 342; Channell and 

Lomolino 2000, pp. 84–86). Of 96 

species whose last remnant populations 

were found either in the core or 

periphery of their historic ranges (rather 

than some in both core and periphery), 

91 (95 percent) of the species were 

found to exist only in the periphery, and 

5 (5 percent) existed solely in the center 

(Channell and Lomolino 2000, p. 85). 

Available scientific data support the 

importance of peripheral populations 

for conservation (Fraser 1999, entire; 

Lesica and Allendorf 1995, entire). 

Based upon the loss of approximately 

58,998,140 acres (238,757 km2) of highquality wolverine habitat from the 

southern extent of the range and the 

adaptive potential that part of the range 

may provide against oncoming climate 

change impacts, and a 12 degree 

latitudinal gap in the North American 

wolverine’s range that would result if 

the U.S. population was lost, we 

determine that the loss of the 

contiguous U.S. wolverine population 

would result in a significant gap in the 

range of the taxon. Thus, the DPS meets 

the definition of significant in our DPS 

policy. 

Marked Genetic Differences 

In the contiguous United States, 

small, isolated wolverine populations 

are likely dependent on gene flow from 

Canada for population persistence 

(Cegelski et al. 2006, pp. 208–209; 

McKelvey et al. 2014, entire). In the 

Northern Rocky Mountains, the best 

available genetic data indicate genetic 


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structuring of populations despite some 

dispersal (Cegelski et al. 2006, pp. 204– 

205, 208; Sawaya et al. 2023, pp. 12–14). 

Genetic structuring reflects the amount 

of interbreeding between different 

groups of an organism where more 

structure indicates less interaction 

between groups, increased genetic 

isolation, increased potential for 

inbreeding, and lower genetic diversity. 

Given the relatively recent 

recolonization of wolverines in the 

contiguous United States from Canada 

(within the last 60–70 years), nuclear 

genetic diversity was lower in the 

southern periphery of the subspecies’ 

range in the south (Sawaya et al. 2023, 

pp. 9–11). Nuclear DNA analyses 

indicated differences in allele 

frequencies between the United States 

and Canada along the Rocky Mountains, 

with some areas of overlap in wolverine 

populations straddling the border due to 

male-mediated gene flow. Females 

appear to be segregated near the 

international border due to their higher 

rates of philopatry (the tendency of an 

animal to remain in or return to the area 

of its birth) than males and their 

apparently greater tendencies to avoid 

crossing major roadways, including the 

Trans-Canada Highway (Highway 1) and 

the Crowsnest Highway (Highway 3) in 

southern British Columbia (Sawaya et 

al. 2023, pp. 12, 17). Both highways 

were opened in the 1960s (British 

Columbia Ministry of Transportation 

and Highways 2001, pp. 16, 20). Since 

then, they have been widened in many 

areas, and traffic volumes have 

substantially increased (British 

Columbia Ministry of Transportation 

and Highways 2001, pp. 7–11, 16–21). 

Mitochondrial DNA patterns in the 

Rocky Mountains showed no unique 

contemporary maternal lineages 

detected south of the international 

border, which is consistent with 

observational data indicating that 

wolverines recolonized the contiguous 

United States from Canada within the 

last 60–70 years (Sawaya et al. 2023, pp. 

2, 16–17). Substantially lower 

mitochondrial DNA diversity in the 

United States, as compared to 

mitochondrial DNA diversity in Canada, 

is consistent with the nuclear DNA 

signals of limited contemporary female 

gene flow between the countries along 

the Northern Rocky Mountain range and 

the wolverine’s relatively recent 

recolonization at the southern edge of 

their range (Sawaya et al. 2023, p. 17). 

In the North Cascades, global 

positioning system (GPS) tracking data 

show that wolverines in western 

Washington and southern British 

Columbia form a small transboundary 

population (Aubry et al. 2023, p. 4). 

Preliminary results from a large 

population genetics study of this 

transboundary population show that 

wolverines in the North Cascades are 

genetically isolated from other 

wolverine populations in the United 

States and Canada and likely went 

through a genetic bottleneck with few 

founders (Sawaya 2023, pers. comm.). 

The population has low heterozygosity 

(less than 0.5) and could be 

experiencing some level of inbreeding 

(Sawaya 2023, pers. comm.). However, 

there are no indications or evidence that 

individuals or population dynamics are 

being adversely affected by inbreeding 

depression (Sawaya 2023, pers. comm.). 

As part of the multi-State wolverine 

occupancy surveys in 2016–2017, 

researchers obtained 240 wolverine 

DNA samples (Lukas et al. 2020, p. 846). 

These samples represented 26 unique 

females and 24 unique males (Lukas et 

al. 2020, p. 846). Analyses of the 

mitochondrial DNA control region 

revealed regional structuring (i.e., 

regional grouping), with all of the 

samples in Idaho, Montana, and 

Wyoming assigned to Haplotype Wilson 

A (the most abundant haplotype in 

North America) and all of the samples 

in Washington assigned to Haplotype 

Wilson C (Lukas et al. 2020, p. 846). 

These results are consistent with the 

latest genetic analysis from the large 

transboundary study (Sawaya et al. 

2023, entire) and previous 

mitochondrial DNA studies showing 

that the Northern Rocky Mountains and 

North Cascades do not appear to share 

any contemporary haplotypes 

(McKelvey et al. 2014, p. 328). 

The genetic differences between the 

contiguous United States and Canada 

consist of lower genetic diversity in the 

United States, a difference that is a 

reflection of the recent recolonization of 

wolverines into the contiguous United 

States from Canada over the last 

century. There are no unique haplotypes 

present in contiguous U.S. wolverines 

that are not already present in larger 

populations in Canada and Alaska. As 

we noted in our analysis in the 

December 14, 2010, 12-month finding 

(75 FR 78030), this is not the kind of 

genetic difference that would lead us to 

conclude that a population is significant 

under our DPS policy. The DPS policy 

is designed to ensure the protection of 

important components of a species’ 

evolutionary legacy rather than 

populations that simply have lower 

genetic diversity due to recent 

recolonization from a larger source 

population. Therefore, as in our 2010 

analysis, we do not find marked genetic 

differences as a basis for determining 

significance for this DPS. 

Summary for Significance 

We evaluated whether the discrete 

population segment of wolverines in the 

contiguous United States is also 

significant, considering factors such as 

whether the population segment is in an 

ecological setting unusual or unique for 

the taxon; whether the loss of the 

discrete population segment would 

result in a significant gap in the range 

of a taxon; whether 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 whether the discrete 

population segment differs markedly 

from other populations of the species in 

its genetic characteristics. We conclude 

that the wolverine population in the 

contiguous United States is significant 

because its loss would result in a 

significant gap in the range of the taxon. 

DPS Conclusion 

Based on the best available 

information, we conclude that the 

population of wolverines in the 

contiguous United States is discrete and 

significant in relation to the remainder 

of the subspecies in North America. As 

a result, the population of wolverines in 

the contiguous United States is a listable 

entity under section 3(16) of the Act. 

The DPS policy sets forth a three-step 

process for determining whether a 

vertebrate population as a separate 

entity warrants listing: (1) Determine 

whether the population is discrete; (2) if 

the population is discrete, determine 

whether the population is significant to 

the taxon as a whole; and (3) if the 

population is both discrete and 

significant, then evaluate the 

conservation status of the population to 

determine whether it is endangered or 

threatened. We have determined that 

wolverines in the contiguous United 

States qualify as a DPS and, therefore, 

are a listable entity. Below, we provide 

a status determination of the wolverine 

DPS in the contiguous United States. 

Summary of Biological Status and 

Threats 

In this discussion, we review the 

biological condition of the DPS and its 

resources, and the threats that influence 

the DPS’s current and future condition, 

in order to assess the DPS’s overall 

viability and the risks to that viability. 

In preparing the 2018 wolverine SSA 

report and the 2023 SSA report 

addendum, we reviewed available 

reports and peer-reviewed literature, 

incorporated survey information, and 


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contacted species experts to collect 

additional unpublished information for 

the North American subspecies (Gulo 

gulo luscus). We identified uncertainties 

and data gaps in our assessment of the 

current and future status of the 

subspecies. We also evaluated the 

appropriate analytical tools to address 

these gaps, consulted with species 

experts, prepared updated maps of the 

known subspecies’ distribution and 

breeding range in the contiguous United 

States, and evaluated new models of 

spring snow. In some instances, we used 

publications and other reports 

(primarily from Fenno-Scandinavia) of 

the Eurasian subspecies (G. g. gulo) as 

a surrogate in completing our status 

assessment. 

Since the publication of the October 

13, 2020, withdrawal document (85 FR 

64618), more than 180 new publications 

have been issued (see list of citations in 

the 2023 wolverine SSA report 

addendum). This is a substantial 

amount of new information for a 

difficult-to-study animal like the 

wolverine and has added significantly 

to our understanding of wolverine 

biology. This new information has also 

highlighted new insights into the 

subspecies’ biological needs, threats, 

and the wolverine’s interactions with 

abiotic and biotic habitat features. 

We also conducted an updated 

geospatial analysis to map verified 

wolverine occurrences and approximate 

breeding ranges in the contiguous 

United States. This was informed by 

recent multi-State monitoring data 

(Lukas et al. 2020, entire; Mosby et al. 

2023, entire). 

Our updated analyses, since the 

publication of the October 13, 2020, 

withdrawal document, of the current 

and predicted future condition for the 

wolverine is presented in the wolverine 

SSA report addendum and summarized 

here. Our future-condition analysis 

includes the potential conditions that 

the subspecies or its habitat may face in 

the future. This includes consideration 

of threats most likely to impact the 

subspecies at the population or 

rangewide scales in the future, 

including potential cumulative impacts. 

The spatial expansion to our climate 

analysis is a major improvement from 

the snow projections used in our 2018 

SSA report, which focused only on 

Rocky Mountain National Park 

(Colorado) and Glacier National Park 

(Montana). We now focus on five 

modeling domains that overlap with 

occupied and potential wolverine 

habitat in the contiguous United States 

across latitudinal, longitudinal, and 

elevation gradients. These include: (1) 

Cascades (Washington); (2) Northern 

Rocky West (Washington, Idaho, and 

Montana); (3) Northern Rocky (Idaho 

and Montana); (4) Mid-Rocky (Idaho, 

Montana, and Wyoming); and (5) 

Southern Rocky (Colorado and New 

Mexico) (Service 2023, p. 49). In our 

updated climate assessment, we use a 

timeframe out to end of century for 

assessing future effects to North 

American wolverine viability from 

climate change and other threats. 

Beyond 2100, climate modeling 

uncertainty increases substantially. Our 

previous assessment considered in the 

October 13, 2020, withdrawal document 

(85 FR 64618) looked at a timeframe 50 

years into the future. We conclude that 

end of century is a reasonable 

timeframe, as it includes the potential 

for observing these effects over several 

generations of the wolverine. 

As discussed above in Analytical 

Framework, we consider what the 

subspecies needs to maintain viability 

by characterizing the status of the 

subspecies in terms of resiliency, 

redundancy, and representation (Wolf et 

al. 2015, entire). Resiliency is having 

sufficiently large populations for the 

subspecies to withstand stochastic 

events (arising from random factors). We 

can measure resiliency based on metrics 

of population health (for example, birth 

versus death rates and population size). 

Resilient populations are better able to 

withstand disturbances such as random 

fluctuations in birth rates (demographic 

stochasticity), variations in rainfall 

(environmental stochasticity), or the 

effects of anthropogenic activities. 

Redundancy is having a sufficient 

number of populations for the 

subspecies to withstand catastrophic 

events (such as a rare destructive 

natural event or episode involving many 

populations). Redundancy is about 

spreading the risk and can be measured 

through the duplication and distribution 

of populations across the range of the 

subspecies. The greater the number of 

populations a subspecies has distributed 

over a larger landscape, the better it can 

withstand catastrophic events. 

Representation is having the breadth 

of genetic makeup of the subspecies to 

adapt to changing environmental 

conditions. Representation can be 

measured through the genetic diversity 

within and among populations and the 

ecological diversity (also called 

environmental variation or diversity) of 

populations across the subspecies’ 

range. The more representation, or 

diversity, a subspecies has, the more it 

is capable of adapting to changes 

(natural or human-caused) in its 

environment. In the absence of 

subspecies-specific genetic and 

ecological diversity information, we 

evaluate representation based on the 

extent and variability of habitat 

characteristics within the geographical 

range. 

Life-History Needs 

Wolverine populations are 

characterized by naturally low densities. 

The species is highly territorial, with 

very little overlap between same-sex 

adults. Wolverines occupy a variety of 

habitats, but generally select habitat in 

locations away from human settlements 

and activities. The wolverine is a snowadapted, cold-climate animal in its 

physiology and morphology (Telfer and 

Kelsall 1984, p. 1830); phylogeography 

(historical processes that may be 

responsible for past and present 

geographic distributions of genealogical 

lineages); and behavior and habits 

(Fisher et al. 2022, p. 7). 

Wolverines consume a variety of food 

resources, and seasonal switching of 

prey is commonly observed. Unlike 

wolverine populations in Eurasia, 

wolverines in the contiguous United 

States rarely prey on livestock. During 

our extensive literature review in 

preparing the 2023 wolverine SSA 

report addendum, we discovered only 

two instances of wolverine depredation 

in the United States since our 2018 SSA 

report; one wolverine that had 

depredated sheep in Utah, and another 

that was caught in a chicken coop in 

Washington (Service 2023, pp. 10, 38). 

Wolverine reproduction includes the 

following characteristics: polygamous 

behavior (i.e., male mates with more 

than one female each year), delayed 

implantation (up to 6 months), a short 

gestation period (30–40 days), denning 

behavior (only observed in snow in the 

contiguous United States), and several 

additional months of maternal care 

(Service 2018, p. 22). The reproductive 

behavior in wolverines is temporally 

adapted to take advantage of the 

availability of food resources, limited 

interspecific competition, and snow 

cover in the winter. 

In our 2018 wolverine SSA report, we 

defined the physical and ecological 

requirements of wolverine in the 

contiguous United States (see (1), (2), 

and (3), below). In light of new 

information regarding wolverine habitat 

associations that provides support for 

the wolverine’s strong preference for 

areas with cold and snowy conditions, 

we have added a fourth ecological 

requirement (see (4), below). The 

requirements are: 

(1) Large territories in relatively 

inaccessible landscapes, at high 

elevation (1,800 to 3,500 m (5,906 to 

11,483 ft)); 


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(2) Access to a variety of food 

resources that vary with seasons; 

(3) Physical/structural features (e.g., 

talus slopes, rugged terrain) linked to 

reproductive behavioral patterns; and 

(4) Habitats characterized by the 

presence of persistent spring snow (of 

greater than or equal to 1 meter on May 

1) for survival and reproduction. 

Our 2023 wolverine SSA report 

addendum affirms these requirements 

and the species characterization in our 

2018 SSA report. 

Habitat 

Research published since our 2018 

wolverine SSA report confirms that 

broad-level habitat selection 

(subspecies’ range, individual home 

range) at the southern edge of the 

wolverine’s distribution can be 

accurately predicted using a small 

number of high-elevation variables and 

terrain features (Carroll et al. 2021a, pp. 

1470–1471; Aubry et al. 2023, p. 7). 

New evidence from around the world 

reinforces that snow—especially 

persistent spring snow—is an important 

predictor of broad-scale wolverine 

distribution and density (Aubry et al. 

2023, pp. 15–16; Carroll et al. 2020, p. 

8; Fisher et al. 2022, p. 10; Glass et al. 

2021, entire; Mowat et al. 2020, p. 220). 

Within home ranges, the precise nature 

of the relationship between wolverine 

space-use and snow is complex, 

involving multiple snow characteristics 

(e.g., density, depth, and melt), various 

phases of the wolverine lifecycle (e.g., 

denning, feeding and food caching, 

within-territory movements, and 

dispersal) and sex-specific habitat 

selection (Carroll et al. 2021, p. 1469; 

Glass et al. 2021, entire; Heinemeyer et 

al. 2019, p. 16). While wolverines 

appear capable of occupying and 

reproducing in areas without persistent 

spring snow in some ecological 

contexts, at a continent-wide scale, 

wolverine dens outside of areas with 

persistent spring snow have thus far 

only been documented to occur in 

colder boreal or arctic environments in 

Canada and Alaska (Aronsson and 

Persson 2017, p. 266; Copeland et al. 

2010, pp. 240–242; Fisher et al. 2022, p. 

8; Jokinen et al. 2019, pp. 6–8; Webb et 

al. 2016, pp. 1466–1467). 

In the Greater Yellowstone Ecosystem, 

distance to high-elevation talus, snow 

water equivalent (a surrogate for snow 

depth), and latitude-adjusted elevation 

were the most important environmental 

factors explaining selection of wolverine 

home ranges and habitats within home 

ranges (Service 2023, p. 16). These 

habitat variables are also known to be 

important in defining the wolverine’s 

distribution (Inman et al. 2013, p. 278). 

Results from dispersal suitability 

models developed for wolverines 

indicate that isolation by landscape 

resistance (areas that individuals are 

less likely to traverse due to high 

energy, mortality, or other biological 

costs) explained more of the variation in 

wolverine genetic differences than did 

isolation by distance (Balkenhol et al. 

2020, pp. 795–797). This means that 

wolverines are moving non-randomly 

across the landscape in association with 

specific landscape features. Snow depth 

(average 1-year snow depth at 1-km2

resolution), terrain ruggedness (measure 

of how jagged or flat the terrain is on 

average), and housing density (census 

block housing density per 1 km2) best 

predicted gene flow in wolverines 

(Balkenhol et al. 2020, pp. 795–797). 

Snow depth was the most important 

variable for explaining variation in 

genetic differences overall (Balkenhol et 

al. 2020, p. 790). At broad spatial scales, 

housing density and terrain ruggedness 

were the most important factors, where 

wolverines avoided areas of high 

housing density and preferred areas of 

terrain ruggedness, which explains the 

variation in wolverine genetic 

differences (Balkenhol et al. 2020, p. 

790). 

In the Cascade Range in southern 

British Columbia and Washington, three 

climatic variables (proximity to the 

transitional zone near the alpine tree 

line, number of frost-free days per year, 

and annual precipitation as snow) were 

correlated with wolverine location data 

(Aubry et al. 2023, p. 10). Wolverine 

distribution in the Cascades is 

constrained by climatic conditions; 

snowy, cold environments delimit the 

areas that are ‘‘overwhelmingly 

associated with resident wolverines’’ 

(Aubry et al. 2023, p. 16). The highestuse areas were on the eastern side of the 

Cascades, where alpine habitats had 

fewer frost-free days (Aubry et al. 2023, 

p. 15). This is consistent with other 

models, indicating that wolverines rely 

on the transitional zone between the 

tree line, below which environmental 

conditions become too warm, and upper 

elevations of permanent ice and snow, 

where there is insufficient food and 

cover to support basic life-history 

requirements for wolverines (Aubry et 

al. 2023, pp. 13–14). 

A study using GPS location data on 38 

wolverines from 2001 to 2010 analyzed 

wolverine home range habitat selection 

across the western United States by 

identifying landscape variables that 

were highly correlated with wolverine 

home ranges (Carroll et al. 2020, entire). 

The resource selection function model 

included landform (e.g., ridges and 

peaks), vegetation classification, 

distance to high-elevation talus, 

latitude-adjusted elevation, average 

monthly snow water equivalent, and 

human modification (Carroll et al. 2020, 

p. 8). Core areas were identified, and 

connectivity was assessed, between 

these core areas using a landscape 

resistance model, validated with GPS 

location data from dispersing 

wolverines (Service 2023, figure 3). 

Results showed that resident wolverines 

in core habitats are far more sensitive to 

low-quality habitat than are dispersing 

individuals, but that dispersers still 

follow lower-resistance pathways that 

connect higher quality core habitats 

(Carroll et al. 2020, p. 9). Another study 

modeled within-home range habitat 

selection by wolverines in areas of the 

Northern Rocky Mountains with high 

amounts of winter backcountry 

recreation and found significant 

differences in male and female habitat 

selection (Heinemeyer et al. 2019a, p. 9). 

The best model for male wolverines 

included distance to roads and 

proportion of lower elevation grass and 

shrub cover, while the best model for 

female wolverines included talus, 

persistent spring snow cover (defined in 

the cited studies as snow cover present 

between April 24 and May 15), and 

forest edge-to-area covariates 

(Heinemeyer et al. 2019a, p. 9). Best 

models for both sexes included 

covariates for topographic position 

index, quadratic form of slope, distance 

to forest edge, solar insulation, and 

percentage cover of forest, riparian, and 

montane open cover types. This study 

also showed that wolverines are 

negatively affected by winter recreation 

(see Disturbance Due to Winter 

Recreational Activity, below). 

Multiple recent studies in Canada 

have provided further evidence of the 

influence of snow cover and human 

development/disturbance on wolverine 

distribution. Wolverine density in and 

around a national park complex in the 

southern Canadian Rocky Mountains 

was three times higher within these 

national parks than outside them, 

increased with spring snow cover, and 

decreased with increasing night light 

intensity (a measure of human 

development) (Barrueto et al. 2022, p. 

4). Along the Front Range of the 

Canadian Rocky Mountains, wolverines 

selected areas with natural land-cover 

and high snow cover and avoided 

anthropogenic features and 

heterospecific competitors (Heim et al. 

2019, pp. 2499–2502). In the Rocky 

Mountains of Alberta, wolverine 

occurrence in space and time was best 

explained by coyote (Canis latrans) 

occurrence and the density of linear 


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disturbance features (e.g., roads, 

pipelines, seismic lines, motorized and 

nonmotorized recreational trails), with 

both of these factors decreasing the 

likelihood of wolverine occurrence 

(Chow-Fraser et al. 2022, pp. 4–5). In 

the southern Canadian Rockies, 

wolverine density was found to be 

positively correlated with the number of 

years of persistent spring snow cover 

and negatively correlated with road 

density (Clevenger 2019, p. 62; Mowat 

et al. 2020, pp. 218–219). Female 

densities in areas with more cumulative 

years of persistent spring snow were 

higher than male densities, which 

suggests there may be a preference for 

snowy areas when denning. An 

additional study, also in the Canadian 

Rockies, found that food availability and 

human disturbance were major drivers 

of wolverine distribution in winter 

(Kortello et al. 2019, p. 7). Persistent 

spring snow was an important factor in 

explaining the variation in female 

wolverine distribution in winter and 

overall wolverine distribution at coarse 

scales (Kortello et al. 2019, p. 8). The 

researchers concluded that their results 

‘‘do not reject the hypothesis that 

wolverine occurrence is constrained by 

an obligate association with persistent 

spring snow’’ (Aubry et al. 2007, p. 

2154; Copeland et al. 2010, p. 244), ‘‘but 

do suggest the alternative explanation 

that the relationship between spring 

snow and wolverine distribution could 

be functionally related to the 

distribution of food, disturbance or 

mortality risk’’ (Kortello et al. 2019, p. 

8). We agree with their assessment and 

acknowledge the precise causal 

mechanism(s) for the apparent 

association of wolverine distribution 

and persistent spring snow are not yet 

clear. There may be a number of factors 

acting in concert to drive the 

wolverine’s preference for cold and 

snowy conditions, and we have 

attempted to account for this in our 

analysis presented in this rule. 

A habitat selection study of 21 adult, 

non-denning wolverines (11 female, 10 

male) fitted with GPS collars in the 

Alaskan Arctic found that wolverines 

generally selected more rugged areas 

closer to streams, rivers, and lakes 

(Glass et al. 2021, p. 893). This study 

also showed that snow characteristics 

are important to wolverines for reasons 

other than solely creating reproductive 

dens. Specifically, they found that nondenning wolverines select deeper, 

denser snow, but only when that snow 

is not undergoing melt (Glass et al. 

2021, pp. 894–895). The wolverine’s 

observed preference for denser snow 

might be a function of both ease of 

movement across the surface, as well as 

the ability of denser snow to maintain 

snow cavities and tunnels (Glass et al. 

2021, p. 895). 

Denning Habitat—Denning habitat 

has been a focus for wolverine 

conservation because wolverines have 

naturally low reproductive rates. 

Impacts to denning habitat could have 

important consequences for 

demographic rates (Fisher et al. 2022, p. 

8). There is growing evidence that 

wolverines rely on subnivean space (the 

environment between snow and terrain) 

for thermoregulation, to escape 

predation risk, and/or to cache food 

(van der Veen et al. 2020, pp. 8–10; 

Fisher et al. 2022, p. 10). Although 

wolverines have been documented 

denning in areas without persistent 

spring snow (Fisher et al. 2022, p. 8; 

Persson et al. 2023, entire), this 

phenomenon appears to be associated 

with cold, high-latitude boreal or arctic 

forests rather than the alpine habitats 

used by wolverines in the contiguous 

United States. In the contiguous United 

States, there is no evidence that 

wolverines have denned in areas 

without persistent spring snow. 

Den-shifting behavior represents a 

tradeoff between moving—and risking 

potential energy loss and harm to 

offspring—versus staying in the original 

den site and risking exposure to 

disturbance or changed conditions, such 

as melting snow, that might make the 

original den site unsuitable (Heeres 

2020, p. 9). In a study in northern 

Sweden focusing on 18 adult female 

wolverines fitted with GPS collars over 

an 11-year period and occupying 271 

den sites, Heeres (2020, p. 15) 

determined that a female used an 

average of 12 den sites during a single 

denning season (range: 4–28; median: 

10). Additionally, female wolverines 

had a higher probability of shifting den 

sites in forested habitats, compared to 

alpine habitats, which is likely a result 

of earlier snow melt in forests that may 

make den sites uninhabitable early in 

the season (Heeres 2020, p. 20). Other 

factors related to den-shifting behavior 

included the level of denning 

experience of the female wolverine, 

which was quantified as the number of 

previous reproductive attempts by an 

individual (lower den-shift probability), 

temperature (higher den-shift 

probability in the warmer forested 

habitats; nonsignificant den-shift 

probability in alpine habitat), food 

resource availability (higher den-shift 

probability, which could be related to 

accessing food or increased human 

presence), and cub age (more shifting as 

cubs mature and are able to move to 

food resources) (Heeres 2020, pp. 20– 

22). 

In certain ecological contexts, 

individual wolverines and reproductive 

dens can exist in areas without 

substantial spring snowpack (Persson et 

al. 2023, p. 10; Jokinen et al. 2019, pp. 

4–9). For example, Jokinen et al. (2019, 

pp. 6, 10) observed seven of eight 

wolverine dens (three primary and five 

secondary dens) in hollows of uprooted 

trees and not in snow; however, the 

researchers acknowledged that sample 

sizes were small and limited their 

ability to draw robust conclusions. 

Jokinen et al. (2019, p. 12) speculated 

that wolverines, in the absence of spring 

snow in Alberta, were able to meet their 

physiological needs through locally 

available features such as the cavity 

created by partially uplifted root 

masses, the thermal properties of thick 

moss, and the caching opportunities 

provided by deep peat accumulations. 

Wolverines are resourceful and may be 

more flexible in their denning 

requirements than documented by 

studies in other landscapes (Persson et 

al. 2023, p. 10; Jokinen et al. 2019, p. 12; 

Glass et al. 2021, entire); however, it is 

also apparent that boreal forest 

communities have a series of unique 

properties conducive to wolverine 

denning, including cold spring 

temperatures and dense peat layers that 

might aid in insulating the den (Jokinen 

et al. 2019, p. 12). 

At present, it remains uncertain 

whether the alpine ecosystems in the 

contiguous United States contain 

environmental conditions that would 

allow wolverines to switch denning 

behavior or use smaller or shallower 

patches of snow in response to changes 

in future snow under a changing 

climate. Even if they were able to make 

this shift, snow may be important to 

wolverines for more than just denning. 

Food Caching—Wolverines are 

physiologically and behaviorally 

adapted to caching perishable food in 

snow, boulders, and peat bogs for shortor long-term storage (van der Veen et al. 

2020, pp. 2–3). In Scandinavia, 

wolverines cached food all year from 

scavenging and predation events, with 

the locations of food caches widely 

distributed across their home ranges 

(van der Veen et al. 2020, pp. 6–8). 

When caching, wolverines selected 

steep and rugged terrain in 

unproductive habitat types (habitats 

with fewer plants and animals) or in 

forest, indicating a preference for lessexposed sites that can provide cold 

storage or protection against pilferage. 

The observed year-round investment in 

caching by wolverines suggests that 

food predictability is important for their 


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survival and reproductive success. 

Increasing temperatures caused by 

climate change may provide new 

challenges for wolverines in at least two 

ways: (1) by decreasing the shelf-life of 

cached food, and (2) by increasing 

competition from pilferers that benefit 

from a warmer climate (van der Veen et 

al. 2020, pp. 8–10). 

Areas of Uncertainty for Wolverine 

Habitat Needs 

The precise causal mechanism(s) for 

the apparent association of wolverine 

distribution and persistent spring snow 

are not yet clear. Hypotheses for this 

association include the importance of 

snow to create dens (Copeland et al. 

2010, entire), the advantages of snow for 

catching prey within a wolverine’s 

metabolic limits (Young et al. 2012, pp. 

224–226), competitive advantages over 

other scavengers and predators in snowcovered areas (Service 2018, p. 6), 

thermoregulation (Service 2018, pp. 7– 

8), food storage and refrigeration (Inman 

et al. 2012, p. 640), or some combination 

of these factors. The interplay of 

temperature and persistence of spring 

snow and the point at which 

temperature becomes limiting is also 

unknown. 

There is presumably some limit in 

appropriate habitat availability at which 

wolverines will not cross certain 

habitats or traverse certain barriers, but 

that threshold is not known. 

Understanding this threshold for 

females is particularly important 

because they often disperse shorter 

distances than males and appear to be 

more affected by potential barriers to 

movement, such as large multi-lane 

highways (e.g., Sawaya et al. 2019, pp. 

621–623). 

Recent studies from Canada and 

Alaska have shown that apex predators 

and sympatric mesocarnivores (small to 

mid-sized carnivores that occur in the 

same area) can influence wolverine 

space use (e.g., Heim et al. 2019, pp. 

2499–2504; Frey et al. 2020, pp. 1133– 

1137; Bell 2021, pp. 46–47; Klauder et 

al. 2021, p. 569; Chow-Fraser et al. 2022, 

p. 4). In addition, it is possible that 

competitors such as coyotes that thrive 

within human-dominated landscapes 

could potentially displace wolverines in 

areas with substantial anthropogenic 

disturbance (Chow-Fraser et al. 2022, 

pp. 4–5). However, the influence of apex 

predators and intraguild competition on 

wolverine distribution, abundance, and 

dispersal in the contiguous United 

States remains largely unstudied. 

Threats 

A species may be determined to be an 

endangered or threatened species due to 

one or more of the five factors described 

in section 4(a)(1) of the Act: (A) The 

present or threatened destruction, 

modification, or curtailment of its 

habitat or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) the inadequacy of 

existing regulatory mechanisms; or (E) 

other natural or manmade factors 

affecting its continued existence. Listing 

actions may be warranted based on any 

of the above threat factors, singly or in 

combination. Threats evaluated for the 

wolverine in the contiguous United 

States include climate change (Factors A 

and E), effects from roads (Factors A and 

E), disturbance due to winter 

recreational activity (Factors A and E), 

other human disturbance (Factors A and 

E), effects from wildland fire (Factor A), 

disease (Factor C), predation (Factor C), 

overutilization (trapping) (Factor B), 

genetic diversity (Factor E), and small 

population effects (Factor E). We found 

that habitat loss as a result of climate 

change is the primary threat to the 

wolverine’s future viability in the 

contiguous United States. We expect 

climate change to exacerbate effects 

from multi-lane roads, backcountry 

winter recreation, and human 

development, all of which could then 

impact genetic diversity and small 

population dynamics. A summary of the 

threats affecting the North American 

wolverine in the contiguous United 

States is presented below; for a full 

description of our evaluation of the 

effects of these stressors, refer to the 

wolverine SSA report (Service 2018, pp. 

57–101) and the 2023 wolverine SSA 

report addendum (Service 2023, pp. 30– 

47). 

Climate Change: The wolverine’s 

evolutionary and phylogeographic 

history suggest a species adapted to cold 

and snowy climate conditions (Fisher et 

al. 2022, p. 7; Service 2023, pp. 24–25). 

The wolverine is a snow-adapted, cold 

climate animal in its physiology, 

morphology (Telfer and Kelsall 1984, p. 

1,830), behavior, and habits. Wolverines 

have been classified as a ‘‘chionphile’’ 

or those animals with adaptations for 

snow (e.g., increased surface area on 

feet, pelt characteristics) (see definitions 

in Pruitt 1959, p. 172; Cathcart 2014, p. 

22). We find that impacts from climate 

change (increasing temperatures and 

decreasing snowpack) have the largest 

potential to influence the North 

American wolverine’s population 

viability in the future. 

To inform our assessment of the North 

American wolverine’s status in the 

contiguous United States, we updated 

our previous climate change analysis, 

the details of which are summarized in 

the wolverine SSA report addendum 

(Service 2023, pp. 47–59). The spatial 

expansion to our climate change 

analysis is a major improvement from 

the snow projections used in our 2018 

SSA report, which focused only on 

Rocky Mountain National Park 

(Colorado) and Glacier National Park 

(Montana). We now focus on five 

modeling domains that overlap with 

occupied and potential wolverine 

habitat in the contiguous United States 

across latitudinal, longitudinal, and 

elevation gradients: (1) Cascades 

(Washington); (2) Northern Rocky West 

(Washington, Idaho, and Montana); (3) 

Northern Rocky (Idaho and Montana); 

(4) Mid-Rocky (Idaho, Montana, and 

Wyoming); and (5) Southern Rocky 

(Colorado and New Mexico) (Service 

2023, p. 49). Central Idaho was not 

modeled due to constraints of time and 

resources. In our updated climate 

assessment, we use a timeframe out to 

year 2100 for assessing future effects to 

the North American wolverine’s 

viability from climate change and other 

threats. Beyond 2100, climate modeling 

uncertainty increases substantially due 

to the inability to predict human 

behavior, policy changes, and, by 

extension, future greenhouse gas 

emissions. Our previous assessment in 

the October 13, 2020, withdrawal 

document (85 FR 64618) looked at a 

timeframe of 38 to 50 years into the 

future. We find that end of century is a 

reasonable timeframe to consider, as it 

includes the potential for observing 

these effects and the wolverine’s 

responses over several generations of 

the wolverine. 

Two scenarios were chosen from the 

Intergovernmental Panel on Climate 

Change (IPCC) Sixth Assessment Report 

to bracket the uncertainty regarding 

future greenhouse gas emission 

scenarios (Tebaldi et al. 2021, p. 258). 

The two emission scenarios used in the 

analyses are referred to as SSP2–4.5 and 

SSP5–8.5; SSPs replace representative 

concentration pathways (RCPs) from 

prior IPCC reports. The numerical 

suffixes (e.g., 2–4.5 and 5–8.5) represent 

the approximate level of radiative 

forcing (the change in energy flux in the 

atmosphere caused by natural or 

anthropogenic factors of climate change) 

in 2100 (compared to preindustrial 

levels) in units of watts per meter 

squared (W/m2). The SSP2–4.5 pathway 

(modest mitigation) used in this analysis 

is similar to the RCP 4.5 scenario used 

in past reports, whereas the SSP5–8.5 

pathway represents one of the most 

pessimistic estimates of future 

greenhouse gas emissions, a future with 

no mitigation policy. The SSP5–8.5 


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pathway was included in this analysis 

to provide a lower-boundary estimate of 

future snow cover available for 

wolverines within the selected domains 

(OSTP 2023, p. 11). We chose a snow 

depth threshold of greater than or equal 

to 1 m (40 inches) to represent 

persistent spring snow cover on May 1 

based on published literature, our prior 

analyses in the 2018 SSA, and studies 

indicating that den site abandonment 

generally occurs before May 1 (see the 

Use of Dens and Denning Behavior 

discussion in the Reproduction and 

Growth section of the 2018 SSA (Service 

2018, pp. 25–27). There is no known 

snow depth threshold for successful 

wolverine denning on any date. 

However, based on historical den site 

melt-out dates (when there was no snow 

at the den sites) and hindcasted 

(historical) snow models for Glacier 

National Park, the 2018 SSA used 

greater than 0.5 m (20 inches) on May 

1. We received criticism from some 

wolverine researchers that the use of the 

0.5-m snow depth threshold on May 1 

was not conservative enough based on 

prior studies (e.g., Copeland et al. 2010, 

entire; McKelvey et al. 2011, entire) that 

considered snow depth out to June. 

Others would argue (based on the 

importance of snow for denning) that 

snow depth at May 1 is not as important 

since young wolverine kits are usually 

out of their natal dens by mid-March 

(Inman 2023, pers. comm.). To address 

the criticism, and to acknowledge that 

snow is likely important to the 

wolverine for more life behaviors than 

just denning, for our updated analysis 

we increased the snow depth measure 

representing persistent snow cover to 

greater than or equal to 1 m (3.3 ft) but 

retained the May 1 end date. This 

provides a reasonable but more 

conservative estimate than we used in 

the 2018 SSA. 

Results from this updated climate 

change analysis are consistent with 

earlier studies predicting greater snow 

loss at lower elevations across all 

domains. Similar elevational patterns 

were reported for Rocky Mountain and 

Glacier National Parks with greater 

reductions in future snow cover at lower 

elevations (Barsugli et al. 2020, pp. 8– 

10). This is partially explained by a 

greater percentage of future 

precipitation falling as rain due to 

higher temperatures, earlier snowmelt 

onset, and warmer conditions. 

Snowpack in the high country is not as 

affected by projected temperature 

increases but is likely more strongly 

controlled by projected precipitation 

changes (Barsugli et al. 2020, pp. 6–11; 

Scalzitti et al. 2016, p. 5367; SospedraAlfonso et al. 2015, p. 4429). 

The elevational distribution of 

historical den sites varies by latitude, 

with a general trend of dens being found 

at higher elevations the farther south 

they are found. For example, dens in the 

Northern Rocky domain are found at 

elevations ranging from approximately 

1,500–2,400 m (4,921–7,874 ft) (Service 

2023, figure 12), while dens in the MidRocky domain are found from 

approximately 2,400–3,000 m (7,874– 

9,843 ft) (Service 2023, figure 13). 

Additional den sites outside of the 

modeling domains could expand these 

elevational bands. The majority of 

historical dens across the domains are 

located in elevational bands that are 

predicted to experience relatively small 

decreases in future snow cover at the 

higher denning elevations and moderate 

decreases for lower denning elevations. 

The percentage change in future snow 

depth threshold (greater than or equal to 

1 m (3.3 ft)) on May 1 (median) for 

SSP2–4.5 (2076–2095) for the upper 

denning elevations in Northern Rocky 

West, Northern Rocky, and Mid-Rocky 

domains is predicted to be a less than 

10 percent decrease, whereas the 

percentage change for the Cascades 

domain is predicted to be a less than 25 

percent decrease. The percentage 

change in future snow depth threshold 

(greater than or equal to 1 m (3.3 ft)) on 

May 1 (median) for SSP2–4.5 (2076– 

2095) for the lower denning elevations 

in Northern Rocky is predicted to be a 

10–50 percent decrease, and for MidRocky is predicted to be a 10–25 percent 

decrease, while the percentage change 

for the Cascades domain is predicted to 

be a less than 25 percent decrease. 

Elevations above historical den 

elevations are predicted to have small 

decreases (less than 10 percent) in the 

future area with snow depth exceeding 

the threshold (greater than or equal to 1 

m (3.3 ft)) on May 1 (median) for SSP2– 

4.5 (2076–2095) across the domains and 

in some cases (e.g., Northern Rocky and 

Mid-Rocky domains), there are increases 

in predicted future area with snow 

exceeding the greater than or equal to 1 

m (3.3 ft) May 1 threshold. This is 

driven by the increases in future 

precipitation expected in all five 

domains, and elevations with 

temperatures sufficiently cold enough to 

sustain snowfall, even with future 

warming. The lowest elevation areas 

within all domains (the lowest 

approximately 500 m (1,640 ft) of 

domains modeled) are predicted to have 

the greatest decreases in the future snow 

depth threshold (greater than or equal to 

1 m (3.3 ft)) on May 1. For example, the 

Northern Rocky domain is predicted to 

experience decreases of 50 to 100 

percent at 1,000–1,500 m (3,281–4,921 

ft) of elevation (Service 2023, figure 13). 

Similar patterns are seen in the other 

four domains, including predicted 

changes (mostly negative) in the future 

snow depth threshold (greater than or 

equal to 1 m (3.3 ft)) on May 1. While 

decreases are projected across the 

domains, the specific thresholds that 

could impact wolverine persistence at 

the population level are not known. 

Central to our assessment of future 

conditions is the degree to which 

changes in persistent spring snow, other 

snow dynamics (e.g., volume, duration, 

condition, spatial and temporal 

variability, etc.), and other climaterelated factors will impact wolverines at 

the population level in the contiguous 

United States. Key uncertainties that 

remain regarding these relationships 

include: (1) the extent to which 

wolverine population connectivity and 

gene flow will be affected by these 

changes; (2) the impacts of climate 

change on ecosystem drivers of 

wolverine persistence (i.e., changes in 

community dynamics, including prey 

availability and competition with other 

predators that might impact wolverine 

demographic rates); (3) the volume and 

duration of snow required for 

wolverines to successfully acquire and 

cache food for future use; (4) the 

impacts of climate change on the ability 

of wolverines to thermoregulate, and 

whether wolverines might experience 

any sublethal effects from changes in 

temperature (e.g., impacts to 

reproduction) (see Thiel et al. 2019, 

entire); (5) whether the observed 

associations of the wolverine’s 

distribution with snowy and cold 

environments are driven by 

reproductive denning needs, other 

ecological requirements, or 

physiological constraints (Aubry et al. 

2023, p. 16); (6) the adaptive capacity of 

wolverines to move to higher elevations 

for denning given predicted snow loss at 

lower elevations within their historical 

denning range (assuming snow is 

required for denning); and (7) the 

importance of snow and the impact of 

decreases in future snow within 

historical denning elevations on 

reproductive success. In summary, 

specific thresholds regarding snow 

dynamics and how changes in these 

factors will impact wolverines in the 

future at the population level remain 

uncertain. 

That said, we know that wolverines 

are a species that is adapted to, and has 

a strong preference for, cold and snowy 

conditions and that these conditions 

occur in the contiguous United States at 

high elevations. As explained before, 


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there are uncertainties as to the exact 

mechanism(s) by which spring 

snowpack is important to wolverines or 

when it may become limiting. Although 

wolverines have been shown to den 

outside of spring snowpack in Canada 

and Scandinavia, we continue to have 

no evidence of this behavioral ability in 

the contiguous United States. 

Furthermore, new research on 

wolverine habitat use continues to 

reinforce that cold and snowy 

conditions are a strong predictor of 

wolverine occurrence on the landscape 

(Aubry et al. 2023, pp. 15–16; Carroll et 

al. 2020, p. 8; Fisher et al. 2022, p. 10; 

Glass et al. 2021, entire; Mowat et al. 

2020, p. 220). Furthermore, deep, 

persistent snow cover has been shown 

to be an important predictor of 

successful wolverine dispersal and 

resulting genetic structure (Balkenhol et 

al. 2020, pp. 798–799). New research on 

food caching indicates that warming 

future conditions could make caching 

food, a year-round behavior, more 

difficult for wolverines (Van der Veen et 

al. 2020, pp. 8–10). As climate change 

reduces the preferred habitat conditions 

for wolverine, it has the potential to 

exacerbate other stressors discussed 

above including effects from roads, 

winter recreational activity, effects from 

development, low genetic diversity, and 

small population effects. When taken 

together, we have no reason to conclude 

that wolverines will somehow continue 

to have the same or better resiliency in 

the contiguous United States in the 

future when those cold and snowy 

conditions at high elevations are 

expected to decrease, with spring 

snowpack at denning elevations 

decreasing as much as 50 percent in 

some areas. Although we are not seeing 

deleterious effects of climate change on 

the contiguous U.S. DPS of North 

American wolverines currently, we 

expect future impacts at the population 

level. 

Effects from Roads: In our 2018 SSA 

and the October 13, 2020, withdrawal 

document (85 FR 64618), we concluded 

that roads present a low stressor to 

wolverines at the individual and 

population level in most of the 

wolverine’s current area of occupancy 

within the contiguous United States. 

New information on the effects of roads 

on the North American wolverine’s 

distribution, density, reproduction, and 

connectivity and gene flow are 

presented below. 

Since 2018, we were made aware of 

four wolverine mortalities from 

collisions with vehicles in the 

contiguous United States, at least three 

of which were males (Service 2023, p. 

30). Overall, young, inexperienced male 

wolverines have a greater risk of road 

mortality during dispersal compared to 

adults and immature females that are 

less prone to long-distance dispersal 

(e.g., Krebs et al. 2004, pp. 497–498). 

The small number of mortalities 

observed since 2018, if biased toward 

males, are unlikely to have substantial 

impacts to the resiliency of the DPS 

overall. 

New studies available in 

southwestern Canada and the western 

United States since the 2018 SSA have 

found that North American wolverine 

distribution and density are negatively 

related to road density (Service 2023, 

pp. 31–32). In southwestern Canada, 

consistency of spring snow and road 

density are the two most important 

variables correlated with wolverine 

density (Clevenger 2019, p. 52; Mowat 

et al. 2020, p. 220). Wolverine 

population estimates derived from 

models based on snow and road density 

predicted that wolverine abundance 

would be 44 percent higher without the 

depressing effect of the road covariate 

(Clevenger 2019, p. 52; Mowat et al. 

2020, p. 220). As most roads are 

concentrated in areas of human 

development at lower elevations with 

less snow, correlations between 

wolverine distribution and road density 

can be confounded by other collinear 

variables (Copeland et al. 2007, pp. 

2210–2211). In southeastern British 

Columbia, the density of forest roads 

that extended into high-elevation 

wolverine habitat was a strong negative 

predictor of wolverine distribution in 

winter, especially for females (Kortello 

et al. 2019, p. 10). The most likely 

explanation for this negative 

relationship is the use of these highelevation forest roads by snowmobilers, 

rather than predator avoidance or 

trapping pressure (Kortello et al. 2019, 

p. 10). Other possible explanations are 

increased trapping access or less 

abundant food resources near roads 

(Mowat et al. 2020, p. 224). While the 

statistical significance of the 

relationship between roads and 

wolverine densities has been 

demonstrated in some areas, the 

mechanisms behind this relationship 

require further study (Mowat et al. 2020, 

p. 224). 

Large transportation corridors (e.g., 

multi-lane highways with substantial 

traffic volume) can have a significant 

impact on wolverine population 

connectivity and gene flow. The 

mechanisms for reducing connectivity 

and gene flow are road mortality and 

reduced habitat permeability (avoidance 

of crossing roads). Mitochondrial and 

nuclear DNA measures of genetic 

population structure found that the 

Trans-Canada Highway corridor in the 

Canadian Rockies, as well as other 

natural and anthropogenic barriers to 

movement, fragmented the North 

American wolverine population by 

restricting female movement (Sawaya et 

al. 2019, pp. 621–622). This restricted 

movement resulted in male-biased 

dispersal and gene flow (Sawaya et al. 

2019, pp. 621–622). This highway is 

approximately 150 miles north of the 

U.S.–Canada border, and the study area 

for analyzing wolverine movement 

across the Trans-Canada Highway was 

in the lower Bow River Valley, which is 

a human-dominated landscape 

containing the Trans-Canada Highway, a 

town with approximately 10,000 

residents, a golf course, three ski areas, 

the Canadian Pacific Railway, and a 

secondary highway. This transportation 

corridor was not an absolute barrier to 

female movement (4 of 20 female 

wolverines crossed the highway during 

the study); however, females traversing 

the transportation corridor did not 

translate to gene flow (Sawaya et al. 

2019, p. 622). The differences between 

male and female dispersal across this 

highway were likely due to the 

exacerbating effects of linear 

anthropogenic barriers on the strong 

natural tendencies for female wolverine 

philopatry (tendency to return to or 

remain near a particular area or site) 

(Sawaya et al. 2019, p. 623). (See 

Genetic Diversity, below, for more 

discussion of the effects of roads on 

gene flow and genetics of wolverines 

within the contiguous United States and 

genetic connectivity to Canada). 

Wildlife crossing structures spanning 

the Trans-Canada Highway along the 

crest of the Continental Divide may 

improve wolverine connectivity across 

this highway. Evidence suggests that 

female wolverines may be starting to use 

wildlife crossings to cross the TransCanada Highway (Service 2023, p. 32). 

However, the efficacy of these structures 

in restoring gene flow has not yet been 

measured (Sawaya et al. 2019, p. 623). 

There are few wildlife crossing 

structures spanning major highways in 

the contiguous United States; a series of 

three under-crossings and one dedicated 

wildlife overpass on I–90 in the 

Washington Cascades (connecting the 

northern and southern Cascades) were 

completed in 2019 (Sugiarto 2022, p. 9). 

To date, however, no wolverines have 

been detected using these relatively new 

crossings. 

Habitats in the contiguous United 

States outside of the known breeding 

distribution of wolverines, including the 

Sierra Nevada in California and the 

central Rocky Mountains in Colorado, 

are separated from occupied habitats by 


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large expanses of high-resistance 

habitats, anthropogenic features, and 

highways (e.g., Carroll et al. 2020, pp. 

9–10; Bjornlie et al. 2021, pp. 116–117). 

While highways are not an absolute 

barrier to movement (wolverines have 

been documented crossing multi-lane 

highways), they can apparently limit 

female wolverine gene flow in some 

situations (e.g., Sawaya et al. 2019, pp. 

621–622). The wolverine’s capacity to 

traverse large expanses of highresistance habitats, anthropogenic 

features, and highways and naturally 

recolonize and establish a population in 

some relatively isolated habitats in the 

contiguous United States (e.g., Oregon 

Cascades, Sierra Nevada, and central 

Rocky Mountains) remains unclear. 

Based on the best available scientific 

and commercial information, the effect 

of roads, in isolation, represents a 

relatively low threat to wolverines in 

the contiguous United States at the 

population level, although some 

individuals are affected. However, in 

combination with other threats 

discussed below, roads, in particular 

multi-lane, high-traffic roads, and high 

road density in core habitats could 

negatively affect the North American 

wolverine’s population resilience, 

distribution, and gene flow in the 

future. 

Disturbance Due to Winter 

Recreational Activity: In our 2018 SSA 

and October 13, 2020, withdrawal 

document (85 FR 64618), we concluded 

that the effect of winter recreational 

activity represents a low stressor to 

wolverines in the contiguous United 

States at the individual and population 

levels. New information on winter 

recreation impacts on North American 

wolverines is presented below and adds 

significantly to our understanding of 

this factor as highly relevant to the DPS. 

The response of North American 

wolverines to various levels of 

backcountry winter recreation 

(motorized and nonmotorized) was 

recently studied in four areas in Idaho, 

Montana, and Wyoming (Heinemeyer et 

al. 2019a, p. 8). The study found that 

wolverines temporarily avoided areas 

within their home range where winter 

recreation (motorized and 

nonmotorized) was occurring 

(Heinemeyer et al. 2019a, p. 16). 

Wolverines increasingly avoided these 

areas as the amount of off-road winter 

recreation increased, resulting in 

indirect habitat loss or functional 

degradation of moderate- or high-quality 

habitats in winter (Heinemeyer et al. 

2019a, p. 16). However, wolverines did 

demonstrate the ability to maintain 

multi-year home ranges despite the 

presence of winter recreation activity 

within those home ranges. Some 

resident animals had more than 40 

percent of their home range within the 

footprint of winter recreation, 

suggesting that, at some scale, 

wolverines tolerate winter recreation 

(Heinemeyer et al. 2019a, p. 16). 

Dispersed or off-road winter 

recreation appears to elicit more of an 

avoidance response than recreation 

along roads and groomed routes with 

females showing more sensitivity than 

males (Heinemeyer et al. 2019a, p. 15). 

Females exhibited more of a negative 

response to motorized recreation, which 

occurred at higher intensity across a 

larger footprint than did nonmotorized 

recreation. 

In a study evaluating the strength of 

aerial survey metrics in predicting 

wolverine responses to motorized and 

nonmotorized backcountry winter 

recreation, higher recreation intensity 

showed stronger avoidance coefficients 

and were the most important modelled 

predictors of female wolverine absence 

(Heinemeyer et al. 2019b, pp. 18–20). 

Given the likelihood that, under climate 

change, both wolverines and 

backcountry winter recreation will be 

impacted by declining snow extent and 

depth and an abbreviated snow season, 

there is the potential for increased 

overlap between winter recreation and 

wolverine distribution (Heinemeyer et 

al. 2019a, p. 18). 

The impacts of motorized and 

nonmotorized backcountry winter 

recreation on wolverines in the Nez 

Perce-Clearwater, Sawtooth National 

Recreation Area, and Salmon-Challis 

National Forests of Idaho were recently 

evaluated (Regan et al. 2020, entire). 

Preliminary results showed that 

recreational impacts, in both area and 

intensity, are increasing over time. In 

the Sawtooth-Boulder White Cloud 

Mountains, researchers compared the 

current extent of winter recreation with 

known historical wolverine home 

ranges and found that most of these 

home ranges contained little or no 

backcountry recreation at this time 

(Regan et al. 2020, p. 4). In contrast, 

recent surveys on the Payette National 

Forest in central Idaho revisited a 

portion of a previous winter recreation 

study and found that there had been an 

incremental loss of resident wolverines 

from 2010 to 2014, and that previously 

documented territories appeared to be 

vacant (Mack and Hagen 2022, p. 13). 

The authors suggest that ‘‘what was 

considered to be a stable core 

subpopulation area could, in fact, be 

more tenuous’’ and ‘‘that the change in 

wolverine abundance in this area might 

be attributed to changes in habitat 

quality from direct or indirect 

influences including dispersed 

recreation,’’ although the cause for the 

decline in wolverine abundance 

requires further study (Mack and Hagen 

2022, p. 13). 

Both motorized and nonmotorized 

recreation can affect wolverine habitat 

use. Forest roads that are used by 

snowmobilers appear to have a strong 

negative correlation with wolverine 

distribution (Kortello 2019, p. 10). 

Nonmotorized recreation can also 

impact wolverines. Remote camerabased surveys from 2011–2020 in 

protected and non-protected habitat in 

southwestern Canada found that 

wolverine detection probability was 

strongly negatively correlated with the 

amount of nonmotorized human 

recreation (Barrueto et al. 2022, pp. 4– 

8). This pattern was consistent in both 

winter and summer, and mirrored the 

findings of Heinemeyer et al. (2019a, p. 

18). Further research is necessary to 

determine the specific causal 

mechanisms most responsible for these 

declines (Barrueto et al. 2022, p. 8). 

In the winter recreation studies we 

considered, winter recreation activities 

varied in the number of recreationists 

and types of recreation, and each study 

area had a unique combination of 

backcountry recreation including 

snowmobile, skiing (including 

snowboards), snowmobile-accessed ski/ 

snowboard, cat-ski, heli-ski, yurtsupported skiing, and snowshoeing. 

Backcountry motorized and 

nonmotorized winter recreation that 

occurs in areas that do not overlap with 

wolverine home ranges is not expected 

to impact the DPS. Additionally, 

developed ski slopes and resorts that are 

already on the landscape and other 

developed winter recreation sites that 

do not occur in the backcountry are not 

expected to be a concern for wolverines, 

as wolverines are likely already 

avoiding these areas. Backcountry 

winter recreational activities that do 

occur in wolverine home ranges could 

negatively impact wolverines by 

displacing them from high-quality 

habitat. Developed ski resorts that allow 

for backcountry or out-of-bounds skiing 

in areas that overlap wolverine home 

ranges may also displace wolverines. 

Backcountry areas where wolverines 

reside in winter are largely difficult for 

recreationalists to access without 

snowmobiles or forest roads that 

facilitate access, and the intensity of 

recreational activity is correlated with 

accessibility. 

Based on the best available scientific 

and commercial information, the effect 

of winter recreation activity (of greatest 

concern because of potential to impact 

denning), in isolation, represents a low 


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threat to North American wolverines in 

the contiguous United States at the 

population level, although some 

individuals are affected. However, in 

combination with other threats, 

including decreased snow availability 

(see Climate Change, above) and 

increased overlap with winter 

recreationalists in the future of climate 

change, winter recreation could 

negatively affect wolverine population 

resilience in the future. 

Other Human Disturbance and 

Development: In our 2018 SSA and 

October 13, 2020, withdrawal document 

(85 FR 64618), we concluded that 

human infrastructure may affect 

individual wolverine behavior (e.g., 

avoidance) or result in the loss or 

modification of wolverine habitat. We 

further stated these effects are small or 

narrow in scope and scale and appear to 

represent a trade-off between foraging 

opportunities in areas that provide 

minimal risk of predation and 

avoidance of open areas and/or higher 

predation risk. We discuss below new 

information related to the impacts of 

human disturbance and development on 

North American wolverine populations. 

North American wolverine density in 

and around a national park complex in 

the southern Canadian Rocky 

Mountains was three times higher 

within these national parks than outside 

them, increased with spring snow cover, 

and decreased with increasing night 

light intensity (a measure of human 

development) (Barrueto et al. 2022, p. 

4). An approximately 40 percent decline 

in wolverine abundance was observed 

between 2011 and 2020, likely from one 

or more of the following causes: 

trapping, backcountry recreation, 

human development, and food 

availability (Barrueto et al. 2022, pp. 4, 

6–8). This pattern is consistent with 

telemetry-based data that wolverines 

avoid infrastructure (May et al. 2006, 

entire; Scrafford et al. 2018, entire). 

Along the Front Range of the Canadian 

Rocky Mountains, wolverines selected 

areas with natural land-cover and high 

snow cover, and avoided anthropogenic 

features and heterospecific competitors 

(Heim et al. 2019, pp. 2499–2502). It is 

thought that competition from other 

carnivores that more readily exploit 

anthropogenic change may exacerbate 

the habitat loss and displacement 

impacts of such changes on North 

American wolverines (Heim et al. 2019, 

pp. 2503–2504). 

Connectivity among North American 

wolverine habitats appears to be 

particularly sensitive to housing 

developments and other human impacts 

in rugged areas located between typical 

wolverine habitats (Balkenhol et al. 

2020, p. 799). Housing density was 

found to be an important predictor of 

long-distance wolverine dispersal and 

population structure in the Northern 

Rocky Mountains (Balkenhol et al. 2020, 

p. 799). Even if areas between wolverine 

primary alpine habitats are not typically 

inhabited by wolverines, they may be 

used during dispersal and can, 

therefore, offer crucial pathways for 

gene flow across broad spatial scales 

(Balkenhol et al. 2020, p. 799). 

The extent of the impacts of human 

presence and actions on the landscape 

have been collectively called ‘‘the 

human footprint’’ (Janzen 1998, entire). 

In an analysis of the human footprint in 

the western United States, Leu et al. 

(2008, p. 1125) found that the physical 

effect area of 14 anthropogenic features 

they analyzed (human habitation, 

interstate highways, Federal and State 

highways, secondary roads, railroads, 

irrigation canals, powerlines, linear 

feature densities, agricultural land, 

campgrounds, highway rest stops, 

landfills, oil and gas development, and 

human-induced fires) covered 13 

percent of the land area in the western 

United States. Accounting for the 

indirect effects radiating out from the 

direct human footprint, Leu et al. (2008, 

p. 1125) categorized 52 percent of the 

western United States as having 

medium- or high-intensity impacts from 

the human footprint (both direct and 

indirect impacts), while low-intensity 

impact areas covered the remaining 48 

percent of the landscape (Leu et al. 

2008, pp. 1125–1127). When modeled 

North American wolverine core areas 

are overlaid across the western United 

States with the human footprint, less 

than 1 percent was in the high-intensity 

category, 12 percent in the mediumintensity category, and 88 percent in the 

low-intensity category. We also overlaid 

the current breeding distribution of the 

North American wolverine with the 

human footprint map and found that 

only 1 percent of the current breeding 

range was within the high-intensity 

category, 31 percent in the mediumintensity category, and 68 percent in the 

low-intensity category (Service 2023, 

figure 4). As expected, wolverine core 

areas are concentrated in high-elevation 

areas with little human infrastructure 

(Service 2023, figure 4). However, 

within their current breeding 

distribution in the contiguous United 

States, wolverines must navigate across 

lower elevation areas with greater 

amounts of human infrastructure to 

disperse from one habitat core to 

another (Service 2023, figure 4). 

In addition to effects on wolverine 

density and connectivity, human 

infrastructure can also affect wolverines 

through shifts in community dynamics 

that precipitate from changes in the 

behavior and temporal use of habitats by 

apex predators. Wolverines and other 

carnivores may shift their daily behavior 

patterns in response to the presence of 

human landscape disturbance (Frey et 

al. 2020, pp. 1133–1138). Indirect effects 

can also include range expansion of 

other carnivores into wolverine habitat 

facilitated by human infrastructure. 

While wolverine and coyotes are 

generally segregated, the probability of 

co-occurrence increases with the 

proportion of linear disturbance features 

(Chow-Fraser et al. 2022, p. 4). Using a 

study area in Alberta (Frey et al. 2020, 

p. 1130), the authors found that while 

wolverines favored areas of low 

disturbance (low proportion of linear 

features) and coyotes favored areas of 

high disturbance (high proportion of 

linear features), co-occurrence 

probability increased 3 times for each 

increase of linear feature unit (ChowFraser et al. 2022, p. 4). Modeling 

showed that competition exhibited the 

strongest effect on wolverine 

distribution, with wolverine occurrence 

best explained by coyote occurrence at 

the same sites (Chow-Fraser et al. 2022, 

p. 4). These results suggest that 

anthropogenic disturbance and resulting 

coyote range expansion may be 

contributing to wolverine population 

declines in the Canadian Rocky 

Mountains (Chow-Fraser et al. 2022, p. 

6). 

A recent study estimated the 

independent and cumulative effects of 

landscape features, human disturbance 

(distance to human settlements and 

roads, night light brightness, human 

population density), and prey 

availability on wolverines and other 

large carnivore occurrences in 

Fennoscandia (region in Europe that 

includes the Scandinavian peninsula, 

the Kola Peninsula, mainland Finland, 

and Karelia) (Milanesi et al. 2022, 

entire). Contrary to the other carnivores 

they evaluated, variation in the 

‘‘permanent’’ occurrence of wolverines 

was best explained by human 

disturbance and the shared effect 

between landscape attributes and 

human disturbance. This same 

relationship was observed for 

‘‘sporadic’’ wolverine occurrences, but 

with a considerably lower level of 

explained variance. The researchers 

concluded that, ‘‘the wolverine showed 

higher sensitivity to human disturbance 

compared to the other large carnivores, 

and spatial segregation patterns between 

wolverines and humans were found, as 

large carnivore home ranges are usually 

at high elevation (often covered by 


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snow), far from the lowlands where 

density of human settlements and roads 

is high’’ (Milanesi et al. 2022, p. 10). It 

appears that wolverines select den sites 

mainly away from infrastructure, 

indicating that successful reproduction 

may be influenced by human activities. 

However, wolverines also appear to be 

able to cross artificial barriers to some 

degree. Therefore, wolverines appear to 

have a relatively low tolerance of 

human disturbance, with an ability to 

exhibit more flexible behavior during 

dispersal in some circumstances. 

Human disturbance and development 

effects are limited in scope and scale 

within the wolverine DPS’s core 

habitats and breeding range in the 

contiguous United States. However, in 

lower elevations and valleys bottoms 

between core habitats, wolverines must 

traverse through areas of human 

disturbance and infrastructure to 

maintain connectivity in the contiguous 

United States, where habitat is often 

fragmented. Wolverines have shown 

avoidance of disturbed areas and human 

infrastructure and a preference for 

habitats devoid of these features. Based 

on the best available scientific and 

commercial information, we find that 

human disturbance and development, 

especially coupled with major roads 

(see Effects from Roads, above), could 

limit wolverine connectivity and 

dispersal in the future. 

Effects from Wildland Fire: In our 

2018 SSA and October 13, 2020, 

withdrawal document (85 FR 64618), 

we found that wildland fire was neither 

a population- nor species-level stressor 

to North American wolverines in the 

contiguous United States. Our 

assessment of wildland fire effects to 

wolverines has not changed. Wildland 

fire can produce both direct and indirect 

effects to wildlife. Direct effects include 

injury and mortality, as well as escape 

or emigration movement away from fires 

(Lyon et al. 2000, pp. 17–21). Wildland 

fire is likely to temporarily displace 

wolverines, which could affect home 

range dynamics. Given that wolverines 

can travel long distances in a short 

period of time, individuals would be 

expected to move away from fire and 

smoke (Luensmann 2008, p. 14). In 

addition, because young wolverines are 

born in underground or otherwise 

sheltered dens during winter months 

and in locations where wildland fire 

risk is low due to snow cover or 

increased moisture (Luensmann 2008, p. 

14), the potential effects of fire at that 

critical life stage is very low 

(Luensmann 2008, p. 14). Indirect 

effects of wildland fire can include 

habitat-related effects or effects to prey 

and competitors/predators; however, we 

are unaware of empirical studies 

evaluating these potential effects as they 

relate to wolverines. 

Given the diversity of habitats 

occupied by wolverines, their 

opportunistic foraging habitats and 

seasonal switching of food sources, their 

occupancy of high elevations, and their 

extensive mobility, wildland fire does 

not represent a stressor to North 

American wolverines in the contiguous 

U.S. range (Service 2018, pp. 63–64) and 

is not expected to have population-level 

impacts. 

Disease and Predation: In our 2018 

SSA, we found that disease and 

predation were neither population- nor 

species-level stressors to the North 

American wolverine in the contiguous 

United States. Our assessment of these 

stressors has not changed. 

There has been considerable localized 

research on diseases and parasites in 

wolverines since the 2018 SSA was 

published; however, we lack data on the 

specific effects to wolverine 

populations. It is conceivable that 

disease-induced mortality could 

contribute to population declines, but 

this remains understudied south of the 

Arctic (Fisher et al. 2022, p. 9). The 

types of bacteria or parasites that could 

lead to disease in wolverines are still 

unknown (Watson 2020, pp. 62, 65). 

Many authors have discovered new 

viruses in the United States and Canada, 

some of which were previously 

unrecognized species of parasites 

(Sharma et al. 2020, p. 277; 2021, p. 1; 

Watson et al. 2020, p. 43; Bandoo et al. 

2021, p. 1). This new information 

pertains to how wolverines act as 

primary hosts for some parasites, such 

as Trichinella spp., and how those 

parasites could increase infection risk to 

humans and other vertebrates (Sharma 

et al. 2021, pp. 1, 7). Considering the 

global coronavirus pandemic in recent 

years and instances of human-animal 

cross-infections, researchers are 

beginning to use genomic data to 

evaluate the wolverine’s susceptibility 

to these pathogens (Lok et al. 2022, pp. 

16–18). Although no coronavirus cases 

have been reported in wolverines, and 

an initial evaluation of the wolverine’s 

genome to determine susceptibility to 

coronaviruses was inconclusive, there is 

potential risk of infection from their 

prey or from researchers handling 

captured wolverines that they release 

back into the wild (Lok et al. 2022, pp. 

16, 18, 20). 

Since our 2018 SSA, we found no 

substantive new information on 

predation. In North America, there was 

one new report of two wolverines being 

predated upon in the boreal ecosystem 

of Canada. One was the result of wolf 

predation, and the other was the result 

of an unknown predator (Scrafford et al. 

2021, p. 9). 

Based on the best available scientific 

and commercial information, disease 

and predation are not threats to North 

American wolverines in the contiguous 

United States at the individual or 

population level. 

Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes: In our 2018 SSA and October 

13, 2020, withdrawal document (85 FR 

64618), we concluded that 

overutilization does not currently 

represent a stressor to the wolverine in 

the contiguous United States at the 

individual, population, or species level. 

We also concluded that trapping in 

Canada had been and appeared to be 

sustainable, and trapping or harvesting 

of wolverines along the contiguous 

U.S.–Canada border did not represent a 

barrier to wolverine movement and 

dispersal along the international border 

(Service 2018, p. 71). Below, we present 

new information on incidental captures 

of wolverines in the contiguous United 

States, where regulated wolverine 

trapping remains closed (Service 2018, 

pp. 70–72), and new information on the 

effects of trapping mortality on 

wolverine populations in southwestern 

Canada. New information suggests that 

wolverine trapping in southwestern 

Canada has impacted connectivity 

across the international border. 

Since 2012, there have been 10 

nontarget wolverine captures (average = 

fewer than 1 per year (1/year)) in 

Montana, resulting in 3 mortalities (1 in 

a conibear (a body gripping trap), 1 in 

a foothold, and 1 in a snare); the 

remainder were released (MFWP 2023, 

in litt., p. 1). In Idaho, 14 nontarget 

captures (0.7/year) of wolverines have 

occurred during licensed trapping 

activities, with no demonstratable trend 

in capture rates over the past 20 years 

(IDFG 2022, in litt., p. 3). Nine 

wolverines were incidentally trapped in 

Idaho between November 2017 and 

August 2022, with two resulting in 

known mortalities (IDFG 2022, in litt., 

pp. 5, 16–22). 

The Idaho legislature revised the 

Idaho Code (IC) in 2021 to: (1) authorize 

a year-round trapping season for wolves 

on private property (IC 36–201(3)); (2) 

authorize additional methods of take 

previously prohibited (inclusive of the 

use of snares in 97 out of 99 

management units) (IC 36–201(2)); (3) 

remove any limit to the number of wolf 

tags an individual may purchase (IC 36– 

408(1)); (4) allow a livestock or domestic 

animal owner to use a private contractor 

to kill wolves (IC 36–1107(c)); (5) allow 

the Idaho Wolf Depredation Control 


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Board to enter into agreements with 

private contractors, in addition to State 

and Federal agencies, to implement the 

provisions of Idaho Senate Bill 1211 (IC 

22–5304(2)); and (6) direct wolf control 

assessments ($110,000 annually) 

collected from the Idaho livestock 

industry to be combined with $300,000 

the State will transfer from the IDFG 

fund annually beginning on July 1, 2021 

(IC 22–5306). 

In Montana, new laws were also 

passed in 2021 to reduce the wolf 

population through, among other things: 

(1) authorizing the use of snares to take 

wolves by licensed trappers (Montana 

Code Annotated (MCA) 87–1–901(2)(b)); 

(2) allowing the Montana Fish, Wildlife, 

and Parks (MFWP) Commission 

authority to extend trapping season 

dates (MCA 87–1–304(8)); and, (3) 

allowing the reimbursement of costs 

incurred to harvest a wolf or wolves in 

Montana (MCA 87–6–214(1)(d)). 

These regulation changes may 

increase the amount of wolf trapping 

and the risk of incidental trapping of 

wolverines because of the use of snares, 

extended trapping seasons, and 

financial incentives. However, because 

wolverines differ from wolves in size, 

distribution, and behavior, trappers use 

pan tension, site selection, and snare 

height to reduce the likelihood of 

incidental capture. In addition, yearround wolf trapping seasons in Idaho 

are limited to private lands, where there 

is very little core wolverine habitat. 

Although the wolf trapping regulations 

have been in effect for a limited time, 

we do not anticipate a significant 

increase in wolverine incidental 

trapping due to the measures Idaho and 

Montana are taking to limit wolverine 

capture. Across the contiguous U.S. 

range, wolverine mortality from 

incidental trapping has historically been 

very low, and States within the DPS’s 

range are actively taking measures to 

limit incidental capture and mortality. 

Below, we present a summary of 

incidental trapping risk and measures to 

limit wolverine capture for each State 

within the current range in the 

contiguous United States. 

California 

The wolverine is listed as both a 

threatened species and as a fully 

protected mammal in California; these 

designations provide wolverines broad 

protection from being trapped, killed, or 

otherwise taken in the State (CDFW 

2023, in litt., p. 2). Recent detections of 

lone animals have indicated the 

occasional presence of wolverines in the 

State (CDFW 2023, in litt., p. 2). 

Recreational and commercial trapping 

of fur-bearing and nongame animals has 

been illegal in California since 2019 

(CDFW 2023, in litt., p. 2). While 

furbearers and nongame species can be 

trapped for other reasons (e.g., the 

protection of property), existing 

regulations likely preclude the serious 

injury or mortality of incidentally 

captured wolverines (CDFW 2023, in 

litt., p. 2). The use of snares, conibeartype traps, and deadfall traps is 

prohibited in large areas of the State, 

including in the most recently estimated 

historical range of the wolverine (CDFW 

2023, in litt., p. 2). The use of steeljawed leghold traps is prohibited 

throughout the State (CDFW 2023, in 

litt., p. 2). All traps must be checked 

daily, and all captured animals that are 

not legal to trap should be immediately 

released (CDFW 2023, in litt., p. 2). 

Colorado 

Recreational trapping of wildlife in 

Colorado is limited to live cage traps 

(CPW 2023, in litt., p. 1), and any 

wolverines incidentally trapped could 

be released unharmed. However, there 

are currently no wolverines known to be 

present in Colorado, and, therefore, 

there should be no incidental trapping 

of wolverines occurring (CPW 2023, in 

litt., p. 1). 

Idaho 

IDFG has multiple guidelines that are 

shared with the trapping community to 

reduce the nontarget capture of 

wolverine (IDFG 2023, in litt.; IDFG 

2022, p. 40). The guidelines, developed 

with the assistance of technical experts 

familiar with the wolverine, include 

recommendations on the types of traps 

used, trap tension, trap placement, 

avoiding areas with wolverine tracks 

observed, selecting habitats less likely to 

have wolverines, and contacting IDFG 

or a local sheriff’s office to assist with 

the safe release of wolverines 

incidentally trapped. These guidelines 

help minimize nontarget wolverine 

captures (IDFG 2023, in litt., p. 3). 

Capture rates of wolverine during 

trapping activities for other species are 

low. In Idaho, 14 nontarget captures 

(0.7/year) of wolverines have occurred 

during licensed trapping activities, with 

no demonstratable trend in capture rates 

over the past 20 years (IDFG 2022, in 

litt., p. 3). Between November 2017 and 

August 2022, IDFG reported that nine 

wolverines were incidentally trapped, 

with two resulting in mortalities (IDFG 

2022, in litt., pp. 5, 16–22). 

Montana 

Montana FWP has multiple trapping 

regulations that help mitigate the 

nontarget capture of wolverines by 

recreational trappers (MFWP 2023, in 

litt., p. 1). The regulations include 

requirements for trappers to take an 

education course, that wolf traps must 

be checked every 48 hours, and that 

wolf trap tension and snare height are 

set to limit wolverine capture (MFWP 

2023, in litt., p. 1). There are also a 

number of regulations required to 

mitigate the nontarget capture of the 

federally listed Canada lynx (Lynx 

canadensis) that are also applicable to 

wolverines, including the prohibition of 

wolf snares on public lands in lynx 

protected zones, which overlap much of 

the wolverine habitat in Montana 

(MFWP 2023, in litt., p. 5). 

The last legal harvest season for 

wolverines in Montana was in 2012 

(MFWP 2023, in litt., p. 1). The 

nontarget capture of a wolverine is very 

rare, and these incidents do not pose 

any population-level effects on 

wolverines (MFWP 2023, in litt., p. 1). 

There have been 10 nontarget wolverine 

captures (average = less than 1/year), 

resulting in 3 mortalities in Montana 

(MFWP 2023, in litt., p. 1). This also 

provides evidence of the efficacy of the 

trapping regulations in place to mitigate 

the nontarget capture of wolverines and 

other animals (MFWP 2023, in litt., p. 

1). 

Oregon 

There is no open season for wolverine 

(or other protected species), and any 

incidental capture or other take of 

wolverines must be reported to the 

Oregon Department of Fish and Wildlife 

(ODFW) within 48 hours (ODFW 2023, 

in litt., p. 4). Regulations that also 

reduce any incidental captures or take 

include a 48-hour trap check (which 

limits the ability for traps to be set in 

the wolverine’s range and allows for 

prompt trap set modification or removal 

if signs of wolverine presence are 

detected) and a prohibition on mediumsized and larger body-grip traps (such as 

the conibear trap) being set on land 

(ODFW 2023, in litt., p. 4). In practice, 

other traps successfully deployed for the 

capture of wolverines simply are not 

used by Oregon trappers (ODFW 2023, 

in litt., p. 4). For example, foothold 

traps (#4 coil springs, Minnesota Brand 

750s) used for wolverine in Canada and 

Alaska are too large for targeted Oregon 

species like bobcats (Lynx rufus) and 

coyotes (ODFW 2023, in litt., p. 4). No 

wolverines have been incidentally 

captured by licensed furtakers in 

Oregon over the last half-century 

(ODFW 2023, in litt., p. 4). 

Utah 

There are no regulations specific to 

wolverines in Utah, but the Utah 

Division of Wildlife Resources (UDWR) 


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regulates trapping and the use of 

trapping devices to reduce the capture 

of nontargeted protected species (UDWR 

2023, in litt., p. 2). Any protected 

wildlife found alive in a trapping device 

must be immediately released 

unharmed (UDWR 2023, in litt., p. 2). 

UDWR also provides trappers with 

multiple recommendations that can 

help avoid catching nontarget species in 

traps set for bobcats and other 

furbearers, including recommendations 

on the type of traps used, placement of 

traps, and baits used (UDWR 2023, in 

litt., p. 2). 

Washington 

Information on the wolverine is in 

Washington’s trapping education 

manual, and all trappers must pass a 

trapper education test (or a similar one 

in another State) prior to obtaining their 

first license (Washington Department of 

Fish and Wildlife (WDFW) 2023, in litt., 

p. 2). Due to Washington’s trap-type 

regulations banning body gripping traps, 

the likelihood of accidental capture of a 

wolverine is very unlikely, and injury or 

death from these traps even more 

unlikely (WDFW 2023, in litt., p. 2). In 

Washington, the most commonly 

trapped animal in habitats that 

wolverines occupy is the marten (Martes 

americana) but marten traps are too 

small for wolverines (even young 

wolverines) to be captured (WDFW 

2023, in litt., p. 2). Larger cage traps that 

are used for bobcat and other larger 

animals could potentially capture a 

wolverine, but these are not commonly 

set in areas that wolverines occupy, and 

if a wolverine were incidentally 

captured, it could be released from the 

trap unharmed (WDFW 2023, in litt., p. 

3). The past several years of trapper 

reports (2017–2022) do not show any 

records of a wolverine being trapped. 

Wyoming 

The Wyoming Game and Fish 

Department (WGFD) addresses the 

incidental capture of animals classified 

as protected, like wolverines, in their 

Furbearing Animal Hunting or Trapping 

Seasons Brochure (WGDF 2023, in litt., 

p. 4). All protected animals that are 

trapped shall be released unharmed and 

mortalities reported to the WGFD 

(WGDF 2023, p. 14). Large areas of 

Wyoming within the distribution of 

wolverines are closed to trapping, 

including Yellowstone National Park 

and Grand Teton National Park. 

The WGFD is not aware of any 

wolverines trapped incidentally in 

Wyoming in recent history (WGDF 

2023, in litt., p. 1). Trap types with the 

potential to capture wolverines are 

largely restricted to private lands, must 

be partially submerged in water (where 

there would be low likelihood of 

wolverine capture), or are required to 

have break-away devices to limit 

bycatch (WGDF 2023, in litt., p. 2). 

Trapping that occurs in areas that 

overlap with wolverine habitat in 

Wyoming is primarily by marten 

trappers that use smaller cubby trap 

sets, and it is unlikely these would 

capture a wolverine (WGDF 2023, in 

litt., p. 2). 

Since our 2018 SSA, there is 

substantial evidence demonstrating that 

direct trapping of wolverines has 

impacted wolverine densities in 

southern British Columbia and Alberta 

over the last decade (e.g., Kortello et al. 

2019, pp. 1, 10; Mowat et al. 2020, 

entire; Barrueto et al. 2020, p. 296; 

Barrueto et al. 2022, entire). In addition, 

there appear to be edge effects from 

trapping, with impacts to wolverine 

densities extending into protected areas 

in southern Canada (Barrueto et al. 

2020, p. 296; Barrueto et al. 2022, p. 4). 

In the most expansive study of 

wolverine trapping and density to 

date—and encompassing southern 

British Columbia and Alberta’s zone of 

connectivity with the Northern Rocky 

Mountains of the United States— 

wolverine trapping mortality was found 

to be unsustainably high at 

approximately 8.4 percent per year 

(Mowat et al. 2020, p. 221). Kill rates 

were higher in the southern British 

Columbia portion of the study area, with 

the best estimate of trapping mortality 

there approaching 10 percent per year 

(Mowat et al. 2020, p. 223). This 

contrasts with the maximum sustainable 

harvest of approximately 8 percent after 

accounting for the influence of higher 

trap vulnerability of juveniles and males 

and stochasticity in juvenile recruitment 

rates (Mowat et al. 2020, p. 221). 

Uncertainties in the stochasticity of 

reproduction, however, had large effects 

on the estimates of maximum 

sustainable harvest, causing it to vary 

between 0 and 8.1 percent (Mowat et al. 

2020, p. 221). Based on their analyses, 

Mowat et al. (2020, p. 224) 

recommended reducing trapping 

mortality to no more than 4 percent per 

year (and perhaps even lower than that 

for an interim period) across their study 

area to promote wolverine population 

recovery. In response to the emerging 

information that trapping rates were 

unsustainable in southern British 

Columbia, the British Columbia 

Ministry of Forests, Lands, Natural 

Resource Operations and Rural 

Development closed a portion of the 

province along the U.S.-Canada border 

to wolverine trapping in 2020. New 

research published since that closure 

has confirmed population declines of 

approximately 40 percent 

(approximately 20 individuals) in the 

wolverine population in a portion of the 

Canadian Rocky Mountains over the 

decade before the closure (Barrueto et 

al. 2022, p. 6). 

Legal trapping of wolverines has not 

occurred in the contiguous United 

States in the past 10 years, and lethal 

incidental trapping of wolverines has 

been minimal (1 to 2 animals per year 

across the contiguous United States). As 

described above, States within the 

wolverine’s range have implemented 

measures to limit the incidental 

trapping of wolverines during legal 

trapping of other wildlife. We expect 

that, as long as trapping is done in a 

manner to limit wolverine bycatch, 

recent changes to wolf trapping 

regulations in Idaho and Montana will 

have little effect on wolverines at a 

population level. 

Based on a recent analysis of an area 

in Canada that was experiencing 

population declines related to 

overharvest, Mowat et al. (2020, p. 224) 

recommended reducing direct trapping 

mortality to no more than 4 percent per 

year across their study area to promote 

wolverine population recovery. In the 

contiguous United States, where there is 

no direct trapping, incidental trapping 

rates have been well below this 

recommended rate. If we assume there 

are approximately 300 wolverines in the 

contiguous United States and assume 2 

wolverine mortalities per year from 

incidental trapping (a conservative 

estimate from the incidental trapping 

mortalities we know of since 2012), that 

would amount to only 0.67 percent of 

the population per year. This minimal 

level of loss will not significantly 

impact the contiguous U.S. population 

of North American wolverines and will 

not inhibit conservation of the DPS. 

As noted, trapping in southern 

Canada appears to be having more of a 

negative effect on wolverine 

populations in Canada than previously 

thought. Unsustainable trapping levels 

in Canada could limit dispersal of 

individuals into the contiguous United 

States, where the dispersal of 

wolverines from southern Canada is 

vital to the genetic and demographic 

health of the U.S. wolverine population. 

Based on the best available scientific 

and commercial information, the effect 

of overutilization (trapping) in the 

contiguous United States is not a threat 

to wolverines at the population level 

because there is no trapping of 

wolverine allowed, and the incidence of 

bycatch of wolverine resulting from 

other lawful trapping activities is small 


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and not expected to impact the DPS’s 

population levels. However, in 

combination with other threats that 

limit dispersal (roads, infrastructure 

development, climate change), 

overharvest of wolverines in southern 

Canada could negatively affect the 

wolverine’s population resilience, 

distribution, and gene flow in the 

contiguous United States in the future. 

Genetic Diversity: In our October 13, 

2020, withdrawal document (85 FR 

64618), we conclude that loss of genetic 

diversity is not a threat for wolverines 

in the contiguous United States now or 

within the foreseeable future. Since our 

2018 SSA and October 13, 2020, 

withdrawal decision, new genetic 

research has become available. Below, 

we assess new information on genetics 

relevant to our status assessment of 

wolverines in the contiguous United 

States, including estimates of effective 

population size and measures of gene 

flow and population connectivity. 

Effective Population Size in the 

Contiguous United States 

As reported in our SSA report 

(Service 2018, pp. 46–47), effective 

population sizes (Ne) are typically 

smaller than census population sizes. 

Scientists use the Ne concept as the 

number of individuals in a population 

that would result in the same loss of 

genetic diversity, inbreeding, and 

genetic drift if they behaved in the 

manner of an idealized population 

(equal sex ratio, random mating, all 

adults producing offspring, equal 

numbers of offspring per parent, and a 

constant number of breeding 

individuals across generations) 

(Frankham 1995, p. 96). The concept of 

effective population size relates to 

population viability because, as a 

general rule, closed populations with 

random mating that have effective 

population sizes (1) below 50 are at 

higher risk of inbreeding depression, 

and (2) below 500 are more likely to lose 

genetic variation important to 

maintaining long-term evolutionary 

potential. Fragmentation can further 

exacerbate inbreeding depression and 

genetic loss, while connectivity to larger 

source populations can alleviate the 

adverse effects of small effective 

population sizes (Frankham et al. 2014, 

p. 60). In addition, small, isolated 

populations are more vulnerable to 

extinction through interactions between 

environmental, genetic, and 

demographic factors (Caughley 1994, 

pp. 221–227). 

The only available estimate of 

effective population size in wolverines 

in the contiguous United States is from 

the Northern Rocky Mountains 

(inclusive of the Greater Yellowstone 

Ecosystem, Idaho, and Montana). This is 

where the bulk of the wolverine 

population in the contiguous United 

States resides (Service 2023, table 4). In 

2009, the Ne estimate for the Northern 

Rocky Mountains was 35 (credible 

interval = 28–52), and Ne did not change 

significantly from 1989–2006 (Schwartz 

et al. 2009, p. 3226). There are no 

published estimates of effective 

population size for wolverines in the 

North Cascades. Therefore, we 

estimated the effective population size 

of wolverines in the North Cascades, 

and the result was an estimate of Ne = 

4 for the North Cascades (Service 2023, 

p. 27). 

Overall, the effective population size 

estimates of wolverines occurring in the 

contiguous United States are small 

compared to conservation guidelines. 

Therefore, wolverines in the contiguous 

United States appear to be vulnerable to 

inbreeding and loss of genetic diversity 

when considered in isolation. However, 

only one or two migrants per generation 

are likely needed to achieve genetic 

population connectivity (Cegelski et al. 

2006, p. 13). If populations were 

connected with a sufficient level of gene 

flow to offset the random loss of genetic 

variation in small populations, it would 

be more appropriate to evaluate the 

effective population size of the 

transboundary, interconnected 

population for the purposes of using 

conservation genetic rules-of-thumb. 

Gene Flow Between the United States 

and Canada 

In the contiguous United States, 

small, isolated wolverine populations 

are likely dependent on gene flow from 

Canada for population persistence 

(Cegelski et al. 2006, pp. 208–209; 

McKelvey et al. 2014, entire). Based on 

simulation analyses of gene loss, a 

census population of approximately 

2,400 adult wolverines in the Northern 

Rocky Mountains and Greater 

Yellowstone Ecosystem would be 

needed to maintain 95 percent of the 

genetic variation over 100 wolverine 

generations (Cegelski et al. 2006, pp. 

12–13). Because there is not likely 

sufficient habitat for that number of 

wolverines in the entire contiguous 

United States (Inman et al. 2013, p. 

282), gene flow on the order of one or 

two wolverines per generation from 

Canada is critical to maintaining genetic 

diversity in wolverines in the 

contiguous United States (Cegelski et al. 

2006, p. 13). 

The best available genetic data 

indicate genetic structuring of 

populations despite some dispersal in 

the Northern Rocky Mountains (Cegelski 

et al. 2006, pp. 204–205, 208; Sawaya et 

al. 2023, pp. 12–14), indicating reduced 

gene flow. Nuclear genetic diversity was 

lower in the southern periphery of the 

subspecies’ range where the recent 

recolonization from Canada occurred 

(Sawaya et al. 2023, pp. 9–11). 

Differences in allele frequencies 

between the United States and Canada 

along the Rocky Mountains are 

observed, with some areas of overlap in 

wolverine populations straddling the 

border due to male-mediated gene flow. 

Females appear to be segregated near 

the international border due to their 

higher rates of philopatry than males, 

and their apparently greater tendencies 

to avoid crossing major roadways, 

including major highways (Highway 1 

and 3) in southern British Columbia 

(Sawaya et al. 2023, p. 12, 17). Traffic 

volumes have substantially increased 

since these highways were opened in 

the 1960s (British Columbia Ministry of 

Transportation and Highways 2001, pp. 

7–11, 16–21). 

No unique contemporary maternal 

lineages have been detected south of the 

international border, which is consistent 

with wolverines recolonizing the 

contiguous United States from Canada 

within the last 60–70 years (Sawaya et 

al. 2023, pp. 2, 16–17). Substantially 

lower mitochondrial DNA diversity in 

the United States, compared to Canada, 

is consistent with limited contemporary 

female gene flow between the countries 

along the Northern Rocky Mountain 

range and the North American 

wolverine’s relatively recent 

recolonization at the southern edge of 

their range (Sawaya et al. 2023, p. 17). 

Wolverines in western Washington 

and southern British Columbia form a 

small transboundary population in the 

North Cascades (Aubry et al. 2023, p. 4). 

Wolverines in the North Cascades are 

isolated from other wolverine 

populations in the United States and 

Canada and likely went through a 

genetic bottleneck with few founders 

(Sawaya 2023, pers. comm.). The 

population has low heterozygosity (less 

than 0.5) and is likely experiencing 

some level of inbreeding (Sawaya 2023, 

pers. comm.). However, there are 

currently no indications of inbreeding 

depression (Sawaya 2023, pers. comm.). 

Population Structure and Gene Flow 

Within Canada 

In our 2018 SSA, we stated that 

wolverines in Canada are considered to 

occur as a single large group because 

they are easily able to move between 

areas of good habitat and because 

wolverine habitat is relatively 

contiguous. New scientific information 

now shows that certain anthropogenic 


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features (e.g., multi-lane highways) limit 

gene flow in southwestern Canada and 

supports previous research showing a 

pattern of decreasing genetic diversity 

in wolverines from north to south (e.g., 

Sawaya et al. 2019, pp. 621–623; 

Sawaya 2023, pers. comm.). Human 

infrastructure and other anthropogenic 

and natural barriers also have the 

potential to impede dispersal and affect 

wolverine population distribution and 

gene flow in Canada (Lofroth and Ott 

2007, pp. 2194–2195). These 

impediments are more prevalent in the 

southern portions of Canada (e.g., 

Lofroth and Ott 2007, p. 2194). 

Additionally, the best available genetic 

data indicate substantial female 

population genetic isolation in 

wolverines (McKelvey et al. 2014, pp. 

328–332; Schwartz et al. 2009, appendix 

A; Zigouris et al. 2012, pp. 1520–1522; 

Sawaya et al. 2023, p. 17), with the 

possibility that the Trans-Canada 

Highway represents a ‘‘continental 

barrier to female wolverine movement’’ 

(Sawaya et al. 2019, p. 623). There is 

also new information that Highway 3 in 

southern British Columbia likely limits 

female wolverine gene flow (Sawaya et 

al. 2023, pp. 17). Therefore, wolverine 

populations in southern British 

Columbia and Alberta near the 

transboundary interface are less 

genetically connected to the contiguous 

United States than we found in our 2018 

SSA. 

Gene Flow Within the Contiguous 

United States 

Previous studies found wolverines 

have a strong association with areas that 

have persistent spring snow cover 

(Copeland et al. 2010, entire). Snow 

depth was the most important variable 

for predicting genetic structure overall 

in a new landscape genetics study in the 

Northern Rockies and at smaller spatial 

scales (up to about 230 km between 

genetic samples); however, at broad 

spatial scales (more than 430 km 

between genetic samples), housing 

density and terrain ruggedness 

explained the most variability in 

wolverine population genetic structure 

(Balkenhol et al. 2020, p. 799). These 

data highlight the importance of 

maintaining dispersal corridors for 

wolverines outside of core habitats, as 

they represent critical pathways for gene 

flow across broad spatial scales 

(Balkenhol et al. 2020, p. 799). 

Analyses of the mitochondrial DNA 

revealed regional structuring (i.e., 

regional grouping), with all of the 

samples collected in Idaho, Montana, 

and Wyoming assigned to Haplotype 

Wilson A (the most abundant haplotype 

in North America) and all of the 

samples in Washington assigned to 

Haplotype Wilson C (Lukas et al. 2020, 

p. 846). Haplotypes are groups of genes 

within an organism that are inherited 

together from a single parent. These 

results are consistent with the latest 

transboundary genetic analysis (Sawaya 

et al. 2023, entire) and previous 

mitochondrial DNA studies showing 

that the Northern Rocky Mountains and 

North Cascades do not appear to share 

any contemporary haplotypes 

(McKelvey et al. 2014, p. 328). New 

information also suggests that 

wolverines in the Greater Yellowstone 

Ecosystem have relatively low genetic 

diversity and high genetic distance from 

other wolverine populations in Idaho 

and Montana (Sawaya et al. 2023, pp. 8– 

9, 15–16). 

The low effective population size and 

low genetic diversity present is likely 

the result of the recent colonization of 

the contiguous United States by 

wolverines from Canada. Relatively few 

migrants per generation would be 

needed to maintain the genetic health of 

wolverines in the contiguous United 

States. New genetic information 

indicates that gene flow across the 

landscape has been impeded by various 

barriers to wolverine (particularly 

female) movement. There is currently 

no evidence of inbreeding depression or 

any deleterious genetic effects in the 

contiguous U.S. population. Based on 

the best available scientific and 

commercial information, the low genetic 

diversity present in the contiguous 

United States is not currently a threat to 

the contiguous U.S. DPS of North 

American wolverine at the population 

level. However, in combination with 

other threats that limit dispersal of 

wolverines (roads, infrastructure 

development, climate change, trapping 

in Canada), the gene flow from Canada 

that is critical to maintaining genetic 

diversity in wolverines in the 

contiguous United States could be 

compromised and lead to future 

deleterious genetic effects to the 

contiguous U.S. DPS of North American 

wolverine. 

Small Population Effects: The number 

of North American wolverines in the 

contiguous United States is relatively 

small compared to the remainder of the 

range in Canada and Alaska, in large 

part due to limited habitat and previous 

persecution and unregulated trapping 

pressures. In our 2018 finding and 

October 13, 2020, withdrawal document 

(85 FR 64618), we considered 

wolverines in the contiguous United 

States to be genetically connected to 

wolverines in Canada, and that 

wolverines in the contiguous United 

States were not separated from the 

larger North American wolverine 

population to the North (Canada and 

Alaska). We concluded that small 

population effects are not a stressor for 

wolverines in the contiguous United 

States now or within the foreseeable 

future. 

Wolverine populations in the 

contiguous United States are small, 

fragmented, and relatively isolated from 

larger populations in Canada (Sawaya 

2023, pers. comm.). Although malemediated dispersal shows some level of 

wolverine population connectivity 

between the United States and Canada 

along the Rocky Mountains, female 

wolverines appear to have virtually no 

recent population connectivity based on 

genetic analyses (Sawaya 2023, pers. 

comm.). Small, isolated populations are 

more vulnerable to extinction through 

interactions of environmental, genetic, 

and demographic factors (Caughley 

1994, pp. 221–227). Stochasticity in 

demographic rates at small population 

sizes causes outsized impacts to vital 

rates, even in a constant environment, 

which can greatly increase extinction 

risk. The repopulation of wolverines in 

the contiguous United States from 

Canada post-unregulated trapping over 

the last approximately 100 years has 

demonstrated the resiliency of the North 

American wolverine population to 

recover from extreme persecution and 

unprecedented direct mortality. We do 

not currently foresee any stochastic or 

catastrophic events that could result in 

a similar population-level effect on 

wolverines in the contiguous United 

States. However, the resiliency of the 

contiguous U.S. population to future 

catastrophic events is predicated on the 

ability of dispersing wolverines from 

Canada to repopulate the contiguous 

United States. As discussed above, 

connectivity with Canada is more 

limited than previously thought, 

especially considering the lack of female 

dispersal, which would be necessary for 

continued repopulation. Based on the 

best available scientific and commercial 

information, the small population size 

present in the contiguous United States 

is not currently a threat to wolverines at 

the population level. However, in 

combination with other threats, the 

small population size of wolverines in 

the contiguous United States could lead 

to a reduced ability of the population to 

withstand catastrophic events in the 

future. 

Conservation Efforts and Regulatory 

Mechanisms 

Federal Regulatory Mechanisms 

Management of the wolverine and its 

habitat on Federal lands is crucial to 


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wolverine conservation, as Federal 

lands make up approximately 96 

percent of modeled wolverine habitat, 

the majority of which are U.S. Forest 

Service lands (Service 2018, p. 103). 

The U.S. Forest Service manages the 

National Forest System lands in 

accordance with local land and resource 

management plans (Forest Plans). In 

2012, the U.S. Forest Service published 

rules for revising Forest Plans (see 77 FR 

21162, April 9, 2012, and 36 CFR part 

219). The 2012 planning rule adopts a 

complementary ecosystem (coarse filter) 

and species-specific (fine filter) 

approach to maintaining the diversity of 

plant and animal communities and the 

persistence of native species in the plan 

area, within U.S. Forest Service 

authority and consistent with the 

inherent capability of the plan area (36 

CFR 219.9). This complementary 

approach includes ecosystem and 

species-specific plan components. 

In our 2018 SSA, we identified Forest 

Plans as important ‘‘federal 

mechanisms’’ that, in combination with 

State wildlife action plans, ‘‘will 

alleviate effects associated with 

potential impacts related to stressors 

discussed in this report.’’ However, in 

our 2018 SSA, we reviewed only four 

Forest Plans and did not identify in 

those plans any specific standards 

(mandatory constraints on project and 

activity decision-making) for 

wolverines. 

For the wolverine SSA report 

addendum, we conducted a more 

comprehensive review of the latest 

Forest Plans for 20 National Forests 

within the current breeding range of the 

contiguous U.S. DPS of North American 

wolverine. We found a complex array of 

plan components aimed at achieving the 

2012 planning rule’s complementary 

ecosystem and species-specific 

approach, while balancing the U.S. 

Forest Service’s multiple-use mandate. 

Some plans provided wolverine-specific 

guidelines, objectives, and direction to 

minimize effects of roads, winter 

recreation, and other sources of human 

disturbance, but we did not identify any 

wolverine-specific standards. The focus 

of wolverine-specific plan components, 

when they were included, was most 

often limited to protection of known 

den sites and maternal habitat during 

the denning season. 

Course-filter protections of habitattypes and ecosystems contained in the 

plans will undoubtably provide some 

conservation benefits to wolverines. For 

example, generally wolverines will 

benefit from wilderness area protections 

(calculated as 18 percent of the extent 

of wolverine occurrence and 41 percent 

of core wolverine habitats in the 

western United States (Service 2018, p. 

103)); limitations on development and 

road construction; limitations on road 

densities in certain areas for the grizzly 

bear (Ursus arctos horribilis) or other 

species; and restrictions on over-snow 

travel. However, quantifying these 

benefits outside of wilderness areas is 

challenging given the variability in 

Forest Plan standards and conservation 

measures across the U.S. range of the 

wolverine. 

U.S. Forest Service regulations require 

National Forests to designate roads, 

trails, and off-road areas that are open 

and closed to motor vehicle use (36 CFR 

212.5). In 2015, the U.S. Forest Service 

published a final rule indicating that it 

will also designate roads, trails, and 

areas open or closed to over-snow motor 

vehicle use (80 FR 4500; January 28, 

2015). These designations are done on a 

Forest-by-Forest basis, resulting in 

variability in the amount of wolverine 

habitat impacted by these designations. 

For example, a recent draft 

environmental assessment for the Idaho 

Panhandle National Forests proposed to 

increase the area available to motorized 

over-snow use, resulting in projected 

increased impacts to primary wolverine 

habitat (from 39 percent currently to 52 

percent under the proposed action) and 

maternal denning habitat (from 44 

percent currently to 52 percent under 

the proposed action) (U.S. Forest 

Service 2023, p. 67). Conversely, the 

Gallatin National Forest reduced the 

amount of area open to over-snow use 

from 42 percent of wolverine denning 

habitat on the Forest to 25 percent (U.S. 

Forest Service 2006, chapter 3–623). 

This variability, and the lack of a 

rangewide assessment that overlays the 

areas of U.S. Forest Service over-snow 

vehicle use closures and wolverine 

habitat, make it difficult to characterize 

the effects of over-snow travel 

management planning on wolverines in 

the contiguous United States. 

Several large National Parks contain 

core habitat for wolverines, including 

Yellowstone, Grand Teton, Glacier, 

North Cascades, and Mount Rainer 

National Parks. These areas are largely 

protected from development, although 

they may be impacted by winter 

recreation to varying degrees. 

Although the Bureau of Land 

Management (BLM) manages relatively 

little land within wolverine core 

habitats, they do manage some of the 

valley bottoms between these core 

habitats. The wolverine is listed as a 

special status species by the following 

BLM offices: Montana/Dakotas (revision 

2020), Idaho (revision 2022), and 

Oregon/Washington (revision 2021). 

The objectives of the BLM’s specialstatus species policy are: (1) to conserve 

and/or recover species listed under the 

Act and the ecosystems on which they 

depend so that the protections of the 

Act are no longer needed for these 

species; and (2) to initiate proactive 

conservation measures that reduce or 

eliminate threats to BLM sensitive 

species to minimize the likelihood of 

and need for listing of these species 

under the Act. We did not identify any 

wolverine-specific standards in BLM 

resource management plans. 

State and Provincial Regulatory 

Mechanisms 

Wolverine trapping remains closed 

throughout the western United States 

and wolverines have retained various 

protected status designations in these 

States (Service 2023, table 10). 

Therefore, legal trapping is no longer an 

active direct stressor on wolverines in 

the contiguous United States. 

Nevertheless, the legacy effects of recent 

overharvest in southern Canada could 

negatively affect the wolverine’s 

population resilience, distribution, and 

gene flow in the contiguous United 

States in the future (see Overutilization 

for Commercial, Recreational, Scientific 

or Educational Purposes, above). 

In response to studies showing that 

wolverine harvest was unsustainable in 

southeastern British Columbia (Mowat 

et al. 2020, entire), the provincial 

government closed Resource 

Management Region 4 (Kootenay) in the 

southeastern portion of British 

Columbia to wolverine trapping and 

imposed a more intensive mortality 

recording system in that region in the 

fall of 2020 (British Columbia 2022, p. 

76). Regions 2 (Lower Mainland) and 8 

(Okanagan) remain closed to wolverine 

trapping under a temporary moratorium; 

therefore, the entire area of British 

Columbia along the U.S.-Canada border 

is now closed to wolverine trapping 

(British Columbia 2022, p. 76). 

Wolverine trapping remains open 

seasonally in British Columbia Resource 

Management Units 3, 5, 7A, 7B, and 

portions of Unit 6 (British Columbia 

2022, p. 76), as well as in the Rocky 

Mountain region of southwestern 

Alberta (Alberta Environment and Parks 

2022, pp. 14–15). 

Resource management units in 

southern British Columbia remain open 

to trapping for several other furbearers, 

and incidental trapping of two 

wolverines has been documented 

following the closure in the Kootenay 

Resource Management Unit to 

wolverine trapping (Vander Vennen 

2020, in litt.). Given the likelihood that 

there is some noncompliance with 

reporting incidental captures, the 


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precise number of wolverines 

incidentally trapped in Canada is not 

known (Vander Vennen 2022, in litt.). 

We note here that we have no indication 

that noncompliance with reporting 

incidental captures is a concern in the 

contiguous United States. There are 

many State regulations and guidelines 

in place to limit incidental wolverine 

trapping, and we have gathered the most 

up-to-date information on incidental 

captures from States within the range 

for inclusion in this rule (see 

Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes, above). 

Aside from regulated taking of 

wolverines, regulatory mechanisms 

available to States for conserving 

wolverines are largely related to 

maintaining habitat conditions that 

support wolverine connectivity. This is 

because the majority of the primary 

habitat cores for wolverines in the 

contiguous United States are on lands 

managed by the U.S. Forest Service. We 

are not aware of any other State 

regulatory mechanisms specific to 

wolverines that limit development, 

winter recreation, or other human 

disturbances in areas important to 

wolverine connectivity in the 

contiguous United States. Several States 

and other organizations, however, are 

implementing a number of voluntary 

monitoring or conservation measures for 

wolverines (see below). 

Voluntary Conservation Measures 

Western States continue to invest in 

monitoring wolverine occupancy. A 

notable effort includes that of the 

Western Association of Fish and 

Wildlife Agencies (WAFWA) Western 

States Wolverine Working Group, now 

referred to as the Forest Carnivore SubCommittee. The purpose of this 

subcommittee is to develop a 

‘‘statistically defensible’’ multi-State 

monitoring plan for States where 

wolverine populations exist (Wyoming, 

Montana, Idaho, and Washington), to 

seek funding to implement the 

monitoring plan, to coordinate 

development of individual State 

wolverine conservation plans for States 

with suitable wolverine habitat, and to 

coordinate and prioritize research 

efforts (WAFWA 2022, p. 1). 

In 2020, the Wyoming Game and Fish 

Department (WGFD) developed a 

wolverine management plan for the 

State of Wyoming that includes 

management and conservation strategies 

in Wyoming. Its goals are to: (1) promote 

long-term wolverine viability, (2) 

support expansion of wolverines into 

suitable habitat, (3) support multi-State 

monitoring efforts, and (4) support 

management of the wolverine as a 

protected animal (WGFD 2020, p. 2). 

Since 2018, Montana Fish, Wildlife 

and Parks has completed 10 habitat 

conservation projects in wolverine 

habitat that conserve 59,725 acres 

through fee title acquisition or perpetual 

conservation easement. A spatial toolset 

is now available for western Montana to 

help prioritize these types of 

acquisitions and easements (Carroll et 

al. 2021b, entire). Other tools such as 

the Crucial Areas Planning System 

(CAPS), a web-based landscape-scale 

planning tool, have also been put in 

place to help guide future developments 

that can impact wolverine habitat 

(MFWP 2022, in litt., p. 6). 

In January 2023, the Idaho Fish and 

Game Commission (IFGC) adopted a 

revised management plan for the 

conservation of fisher (Pekania 

pennanti), wolverine, and Canada lynx. 

This plan provides updated guidance 

and identifies management priorities for 

the conservation of this suite of species 

over the next 6 years in Idaho. These 

priorities include four objectives and 

step-down actions related to 

connectivity, climate, incidental 

trapping, and increasing our knowledge 

of the relationship of wolverine denning 

and snow. Under the objective of 

addressing connectivity, IFGC proposes 

to continue contributing to the 

transboundary landscape genetics study, 

to develop products to support project 

planning and review, to develop 

voluntary partnerships to facilitate 

protections of important areas for 

movement and dispersal, to provide 

technical assistance to licensing and 

permitting authorities, and to maintain 

and to conserve wolverine populations 

and habitats through cooperative 

agreements. For the climate change 

objective, IFGC intends to improve 

modeling and monitoring. For the 

incidental trapping objective, IFGC 

intends to continue providing guidance 

and mandatory training to minimize 

nontarget capture of wolverines in traps. 

Lastly, to fill knowledge gaps, IFGC 

proposes to identify denning sites and 

will, if feasible, develop a model to 

predict denning areas to inform land 

management planning efforts. 

The Utah Wildlife Migration 

Initiative, founded in 2017, identifies 

and protects connective corridors that 

allow fish and wildlife to migrate to 

necessary habitat areas around the State. 

The mission is to document, preserve, 

and enhance wildlife movement for 

species throughout Utah using state-ofthe-art tracking and data management 

technologies, strong collaborative 

partnerships, and compelling outreach. 

The Migration Initiative and its partners 

are mapping the movements of wildlife, 

including wolverines, so crossing 

structures can be placed in areas that 

coincide with movement corridors. 

Similar work is being conducted in 

other States and is coordinated between 

States. 

Colorado Parks and Wildlife had 

previously considered reintroducing 

wolverines to Colorado as a 

nonessential experimental population to 

further their conservation (see 78 FR 

7890; February 4, 2013). However, that 

proposal was withdrawn in 2014, when 

we withdrew our proposed listing rule 

(see 79 FR 47522; August 13, 2014). 

There is currently no formal proposal to 

reintroduce wolverines to Colorado. 

Since 2019, Woodland Park Zoo has 

been coordinating the Washington 

Wolverine Research and Monitoring 

Group, a coalition of researchers and 

conservationists who lead wolverine 

projects in Washington (Woodland Park 

Zoo 2022, in litt.). The goal of this group 

is to help advance North American 

wolverine research and monitoring in 

Washington by strengthening 

communication and collaboration 

among wolverine projects Statewide. 

This group meets several times a year to 

discuss research efforts, share results 

and insights, and strategize around 

wolverine research and conservation in 

Washington. 

Summary of Conservation Efforts and 

Regulatory Mechanisms 

The various Federal, State, and 

provincial regulatory mechanisms and 

voluntary conservation efforts described 

above are expected to provide some 

benefit to North American wolverine 

conservation in the contiguous United 

States. However, these mechanisms and 

efforts are inadequate to protect the 

subspecies from the impacts of climate 

change in the future when the cold and 

snowy conditions this subspecies is 

adapted to are expected to decrease. 

Summary of Current Condition 

Currently, in the contiguous United 

States, North American wolverines are 

distributed in five primary core areas 

(identified as management regions in 

Inman et al. 2013), including the 

Northern Cascades in Washington; the 

Salmon-Selway in central Idaho, 

including the Wallowa Mountains of 

northeastern Oregon; the northern 

Continental Divide in northwest 

Montana; the Central Linkage region of 

Idaho and Montana; and the Greater 

Yellowstone Ecosystem (Service 2023, 

figure 14). Although long-distance 

dispersers (primarily males) 

occasionally reach potentially suitable 

habitat in other regions, known breeding 


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populations are currently limited to 

these core regions. 

The precise size of the wolverine 

populations in the contiguous United 

States are currently unknown but may 

be small due in part to their large 

territories and the limited amount of 

available habitat in the contiguous 

United States. Estimates based on 

extrapolations of densities and suitable 

habitat suggest there could have been 

approximately 318 wolverines (95 

percent CI = 249–926) in the contiguous 

United States more than a decade ago 

(Inman et al. 2013, p. 282). The best 

available estimates of effective 

population size of wolverines in the 

contiguous U.S. portions of the 

Northern Rocky Mountains and North 

Cascades are likely fewer than 50 

combined (Schwartz et al. 2009, p. 

3226). 

We evaluated previously modeled 

wolverine primary habitat in the 

contiguous United States (Inman et al. 

2013, entire) and estimated that 96 

percent of this area is owned or 

managed by Federal agencies and 41 

percent of this area is located in 

designated wilderness areas (Service 

2018, p. 72). Within Idaho, Montana, 

Washington, and Wyoming, non-spatial 

occupancy model estimates were 

slightly lower in 2021–2022 (mean 

occupancy = 0.33; 95 percent CI 0.21– 

0.34) compared to 2016–2017 (mean 

occupancy = 0.27, 95 percent CI 0.27– 

0.39), but with overlapping confidence 

intervals (Mosby et al. 2023, p. 4; 

Service 2023, table 2). Despite 

overlapping confidence intervals, 

Bayesian analysis revealed an 85 

percent chance that the occupancy 

estimate from 2021–2022 was outside 

the 95 percent CI of the 2016–2017 

occupancy estimate (Mosby et al. 2023, 

p. 4). The percentage of surveyed cells 

that were occupied decreased between 

the sampling periods in Montana (43.7 

to 17.0 percent) and Washington (34.6 to 

12.5 percent), increased in Wyoming 

(11.5 to 25.5 percent), and remained 

relatively unchanged in Idaho (33.8 to 

34.5 percent) (Service 2023, table 2). 

Spatial occupancy models by 

geographic area showed substantial 

differences between the sampling 

periods, with both lower and higher 

occupancy probabilities depending on 

the geographic area (Service 2023, table 

3; Mosby et al. 2023, pp. 4–7). Although 

no wolverines were detected during the 

2021–2022 survey in the sampled cells 

of Oregon, Utah, or Colorado (Service 

2023, table 2), recent wolverine 

detections from other research efforts or 

incidental observations have been 

reported in Oregon, Utah, and California 

(Service 2023, p. 6). Despite differences 

between the sampling periods, Mosby et 

al. (2023, p. 7) indicate that 

interpretations of the relationship 

between the two estimates be 

considered cautiously, and that repeated 

surveys into the future will be helpful 

in ultimately interpreting any trends in 

occupancy estimates. The reasons for 

the observed changes in occupancy by 

geographic region are not yet clear, and 

could be sampling anomalies, a real 

shift in distribution, or some 

combination of factors (Mosby et al. 

2023, p. 7). This aligns with our analysis 

of wolverine observations from State 

wildlife agencies, the U.S. Forest 

Service, the National Park Service, 

Tribes, researchers, and others in the 

western United States from 2009–2022, 

which shows wolverines continue to 

occupy much of the core habitat within 

their breeding range in the contiguous 

United States (Service 2023, figure 2). 

Contiguous U.S. contemporary 

wolverine populations are most likely 

descendants of immigrants from Canada 

(Service 2018, p. 49). Wolverine genetic 

diversity in the contiguous United 

States is relatively low, and there are no 

known unique mitochondrial DNA 

haplotypes present in contiguous U.S. 

wolverine populations (Sawaya et al. 

2023, pp. 10–11). Due to the limited 

amount of potential wolverine habitat in 

the United States, connectivity and gene 

flow with Canada is necessary for the 

long-term genetic health and viability of 

wolverines in the western United States. 

In the North Cascades, new GPS 

tracking information shows that 

wolverines in western Washington and 

southern British Columbia form a small 

transboundary population (Aubry et al. 

2023, p. 4), although they are isolated 

from other wolverine populations in the 

United States and Canada (Sawaya et al. 

2023, pp. 9–13, 16). In the Northern 

Rocky Mountains, the best available 

data indicate genetic differences 

between populations despite some 

(mostly male-mediated) gene flow 

(Cegelski et al. 2006, pp. 204–205, 208; 

Sawaya et al. 2023, pp. 12, 17). 

Measurable differences have been 

reported in mitochondrial DNA 

haplotype diversity and nuclear 

microsatellite DNA allele frequencies 

between the U.S. Rocky Mountain 

populations and Canada populations 

(Cegelski et al. 2006, p. 203, Sawaya et 

al. 2023, pp. 12, 17). There is currently 

no evidence of inbreeding depression in 

wolverine populations in the contiguous 

United States; however, there is 

potential for inbreeding given the 

relatively small population sizes of 

wolverines here, especially in the 

Cascades (Sawaya 2023, pers. comm.). 

Wolverine populations in much of 

North America are still recovering from 

large losses of individuals from 

intensive hunting and unregulated 

predator control in the late 1880s into 

the mid-20th century (Service 2018, p. 

104). Trapping and poisoning from the 

late 1800s/early 1900s contributed to 

extirpation in the contiguous United 

States during that time, but individuals 

have come back (from Canada) over the 

years since. Trapping or hunting of 

wolverines remains prohibited in the 

United States, and mortality from 

incidental trapping is currently rare. 

Over the past century, there has been 

enough connectivity with Canada for 

wolverines to repopulate the contiguous 

United States. New genetic research 

provides further evidence of this 

recolonization via dispersers from 

Canada (Service 2023, pp. 27–28). 

However, connectivity in recent years is 

less certain. 

In our October 13, 2020, withdrawal 

document (85 FR 64618), we 

determined that wolverines in the 

contiguous United States were 

connected to and an extension of the 

Canadian population. We now know 

that there are potential barriers to recent 

movement of wolverines to and from the 

contiguous United States, as evidenced 

by the genetic profile of wolverines in 

the contiguous United States (Sawaya et 

al. 2023, entire). Trapping in Canada 

near the international border was 

thought to be occurring at sustainable 

levels at the time we published our 

October 13, 2020, withdrawal document 

(85 FR 64618). In a portion of 

southwestern Canada encompassing a 

Rocky Mountain National Park complex 

and surrounding unprotected lands, the 

wolverine population declined 

approximately 40 percent 

(approximately 15–20 wolverines) from 

2011–2020, likely due largely to 

overharvest through trapping (Barrueto 

et al. 2022, p. 4). This area may be an 

important source of dispersing 

individuals, and overharvest could 

reduce pressure for surplus wolverines, 

particularly females, to disperse south 

towards the contiguous United States. In 

addition, genetic analysis shows that 

recent dispersing individuals from 

Canada have been exclusively male 

wolverines and major highways in 

Southern Canada appear to limit female 

dispersal (Sawaya et al. 2023, pp. 12–14, 

17). Also, various studies that have 

come available since the 2018 SSA 

report reinforce the understanding that 

wolverines avoid areas of significant 

human development and that 

development may inhibit dispersal of 

wolverines between home ranges and 


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habitat patches (Service 2023, pp. 34– 

36). Even though there is low genetic 

diversity in the contiguous U.S. 

population, the population is relatively 

small, and habitat is somewhat 

fragmented, there is no current evidence 

of inbreeding depression in contiguous 

U.S. wolverines and the population 

appears stable from an occupancy 

perspective. 

We evaluated several threats that may 

be affecting wolverine populations or 

their habitats, including effects from 

roads, disturbance due to winter 

recreational activities, human 

disturbance and development, effects 

from wildland fire, disease and 

predation, overutilization, genetic 

diversity, small population effects, and 

climate change. Although these threats 

may affect individual wolverines, none 

of these threats is currently impacting 

wolverine resiliency (the subspecies’ 

ability to rebound from environmental 

stochasticity) in the contiguous United 

States at a population level. In the 

future, the synergistic effect of some of 

these threats coupled with the impact of 

climate change (increased temperatures 

and decreased spring snowpack) could 

reduce resiliency of the contiguous U.S. 

population (see Summary of Future 

Condition, below), although climate 

change is not currently impacting the 

DPS. Currently, the contiguous U.S. 

population appears resilient because 

despite the potential threats analyzed, 

the population continues to show 

stability and wolverines occupy a large 

portion of the available habitat in the 

western United States, providing 

redundancy to withstand potential 

catastrophes. Wolverine breeding 

populations in the western United 

States are currently distributed across 

four unique ecoregions (Service 2023, 

figure 16). This ecoregion variation can 

correlate with species-wide 

evolutionary potential, providing 

representation (the ability to adapt to 

changes in the biological and physical 

environment). The North American 

wolverine’s wide distribution across 

multiple ecoregions and differential 

exposure to various stressors also 

affords the DPS redundancy against 

catastrophic events. Overall, the current 

resiliency, redundancy, and 

representation of the contiguous U.S. 

population of wolverines supports 

current DPS viability. 

Summary of Future Condition 

In the wolverine SSA report 

addendum, we provide a 

comprehensive analysis of the future 

condition of wolverines in the 

contiguous United States, which we 

summarize here (Service 2023, pp. 61– 

69). Wolverine habitat in the contiguous 

United States is projected to decrease 

and become more fragmented by the end 

of the century as a result of climate 

changes that result in increasing 

temperatures, earlier spring snowmelt, 

and loss of deep, persistent spring 

snowpack, primarily at lower elevations 

(see Climate Change, above). Winter 

recreation, which has been shown to 

negatively influence wolverine behavior 

during an important time of year when 

females are denning and raising young, 

in these diminished habitats may 

increase as human populations increase 

(U.S. Forest Service 2016, pp. 12–14). In 

addition, snow-dependent recreation 

that was formerly distributed over a 

wider elevation gradient will be 

constrained to that part of the gradient 

that contains quality snow into the 

future. Concurrently, human 

development may continue to expand in 

areas between core habitats that are 

important for maintaining wolverine 

population connectivity. While 

wolverines are capable of crossing areas 

with some human disturbance during 

dispersal, they also have shown some 

sensitivity to human development and 

other human impacts in rugged areas 

located between typical core wolverine 

habitats (Balkenhol et al. 2020, p. 799; 

Barrueto et al. 2022, p. 4). Increased 

human development, infrastructure, and 

associated anthropogenic disturbance 

are expected to have direct and indirect 

effects to wolverine populations in the 

contiguous United States, including 

reducing the number of wolverines that 

can be supported by available habitat, 

reducing the ability of wolverines to 

travel between patches of suitable 

habitat, and reducing potential 

dispersers from Canada. A reduction in 

population size and connectivity within 

the contiguous United States and with 

Canada may affect metapopulation 

dynamics, making it more difficult for 

subpopulations to recolonize currently 

extirpated areas and augment the 

genetics or demographics of adjacent 

subpopulations. We expect wolverine 

resiliency and redundancy in the 

contiguous United States to decline in 

the future. 

We have identified significant 

uncertainties that hamper our ability to 

predict the scope, scale, and timing of 

future demographic outcomes for 

wolverines in the contiguous United 

States. These include uncertainties in 

mechanistic habitat relationships; 

census and effective population sizes; 

and the cumulative impact of multiple 

stressors on population connectivity, 

survival, and reproduction. 

Nevertheless, habitat loss through 

climate change, combined with other 

stressors, is likely to negatively impact 

wolverines in the contiguous United 

States over the next century by reducing 

resiliency, redundancy, and 

representation. Moreover, there are few 

actions that are reasonably certain to 

occur in the future that would 

compensate for these negative impacts. 

We evaluated the contiguous U.S. 

DPS of North American wolverine’s 

ability to respond to environmental 

change in two ways. First, we examined 

core attributes of the contiguous U.S. 

DPS of North American wolverine’s 

adaptive capacity in relation to 

standardized attributes to characterize 

the likelihood that wolverines in the 

western United States will be able to 

adapt to changed conditions 

(representation) (Thurman et al. 2020, 

entire; Service 2023, figure 15). Second, 

we evaluated the current and potential 

distribution of wolverines across 

ecological regions of the western United 

States given that ecological changes may 

vary across space and that wolverines in 

different ecological contexts may have 

dissimilar responses to these changes. 

The contiguous U.S. DPS of North 

American wolverine’s ability to adapt to 

climate change and other environmental 

changes, its adaptive capacity 

(representation), is key to reducing its 

vulnerability to these changes. Our 

qualitative adaptive capacity analysis 

for the contiguous U.S. DPS of North 

American wolverine was based on lifehistory characteristics and shows that 

several intrinsic factors make North 

American wolverines susceptible to 

negative outcomes from future 

environmental change (Service 2023, 

pp. 66–69). Their specialized habitat 

associations, low genetic diversity and 

population size, narrow ecological 

niche, low tolerance for human 

disturbance, and slow reproductive rate 

all contribute to the contiguous U.S. 

DPS of North American wolverine’s 

relative difficulty in adapting in-place to 

future environmental change (Service 

2023, table 14). Factors that may 

partially mitigate the contiguous U.S. 

DPS of North American wolverine’s low 

adaptive capacity are their ability to 

disperse long distances, their relatively 

wide distribution in the Northern Rocky 

Mountains and in the North Cascades 

(albeit in a narrow climactic niche), and 

their flexible diet (Service 2023, table 

14). Stressors that lessen the ability of 

North American wolverines to disperse, 

or that decrease their distribution, are 

likely to also degrade their adaptive 

capacity (redundancy), leaving them 

more vulnerable to environmental 

change. 


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Maintaining a species, or in this case 

a subspecies, across its full breadth of 

ecological variation can reduce 

extinction risk (Forester et al. 2022, p. 

512). To further assess the contiguous 

U.S. DPS of North American wolverine’s 

future evolutionary potential, we 

examined the DPS’s current distribution 

across different ecoregion provinces. 

Ecoregion provinces incorporate 

temperature, precipitation, and 

vegetation data, and therefore represent 

landscapes with similar environmental 

traits (Bailey 2016, entire). Wolverine 

breeding populations in the western 

United States currently exist in 4 of 10 

ecoregions where there is potential 

wolverine core habitat (Service 2023, 

figure 16). Outside of the area with 

known wolverine breeding, several 

ecoregions in the western United States 

contain only a relatively small area of 

potential wolverine core habitat. Except 

for the Sierran Steppe-Forest-Alpine 

ecoregion, wolverine breeding 

populations currently inhabit all the 

ecoregions of the western United States 

with large contiguous blocks of 

potential wolverine core habitat (Service 

2023, figure 16). 

Despite their relatively wide 

distribution among ecoregions, 

wolverines in the contiguous United 

States have low genetic diversity 

compared to Canadian populations and 

are unlikely to have evolved specialized 

adaptations to southern climates given 

their recent recolonization following 

extirpation (McKelvey et al. 2014, p. 

332). The historical population of 

wolverines in the Sierra Nevada may 

have possessed unique evolutionary 

potential given the distinct genetic and 

taxonomic characteristics of historical 

museum samples; however, the 

wolverines in the Sierras were 

extirpated in the early 1900s, and their 

matrilines were eliminated from North 

America (McKelvey et al. 2014, p. 332). 

Nevertheless, the DPS’s distribution 

across multiple ecoregions means that 

parts of their range may have less 

exposure to future stressors. Expansion 

into unoccupied ecoregions where there 

is suitable habitat could further decrease 

their risk of exposure to future stressors. 

Wolverine populations in the 

contiguous United States are currently 

small, fragmented, and relatively 

isolated from larger populations in 

Canada (Cegelski et al. 2006, pp. 206– 

207, 210; Sawaya 2023, pers. comm.). 

Although male-mediated dispersal 

shows some level of wolverine 

population connectivity between the 

United States and Canada along the 

Rocky Mountains, female wolverines 

appear to have virtually no recent 

population connectivity based on recent 

genetic analyses (Sawaya 2023, pers. 

comm.). Small, isolated populations are 

more vulnerable to extinction through 

interactions between environmental, 

genetic, and demographic factors 

(Caughley 1994, pp. 221–227). 

Stochasticity in demographic rates at 

small population sizes causes outsized 

impacts to vital rates, even in a constant 

environment, which can greatly increase 

extinction risk. Small, isolated 

populations also lose genetic diversity 

over time, primarily through inbreeding 

and genetic drift, which can exacerbate 

extinction risk if demographic rates are 

further degraded through inbreeding 

depression (Benson et al. 2016, p. 8). 

Low genetic diversity can also reduce 

future adaptive capacity and 

evolutionary potential, reducing 

representation. 

Although historical wolverine 

populations were likely naturally small 

and distributed among patches of highelevation alpine habitats in the 

contiguous United States, core 

wolverine habitats in the contiguous 

United States are projected to become 

smaller and more fragmented in the 

future as a result of climate change and 

human disturbance. These changes may 

degrade the DPS’s resiliency and 

redundancy over time, although there 

are uncertainties in the precise amount 

of degradation, how much this 

degradation will affect wolverine 

viability in the contiguous United 

States, or the time period over which 

the degradation would happen. Despite 

their current distribution across several 

ecological regions of the West, the core 

attributes related to adaptive capacity 

exhibited by wolverines may limit the 

ability of this DPS to adapt and persist 

in the face of projected environmental 

change. Long-distance dispersal and 

recolonization of some of the larger 

areas outside of the current breeding 

range of the contiguous U.S. DPS of 

North American wolverine (e.g., Sierra 

Nevada and central Rocky Mountains) 

could partially mitigate their 

susceptibility to environmental change. 

Dispersal between currently occupied 

core habitats may become more difficult 

in the future with anticipated increases 

in human development between the 

alpine core areas and increased 

backcountry winter recreation in core 

habitats. However, wolverine dispersal 

could be maintained or improved by 

human intervention (e.g., conserving 

wildlife corridors between alpine 

habitats, constructing highway crossing 

structures for wildlife). 

Overall, the wolverine population in 

the contiguous United States is expected 

to decrease in resiliency, redundancy, 

and representation in the future. We 

acknowledge that new information 

suggests populations in the contiguous 

United States may be less secure in the 

future than we described in our 2018 

SSA and October 13, 2020, withdrawal 

document (85 FR 64618). We also 

acknowledge that uncertainty remains 

around gene flow between the United 

States and Canada, core habitats and key 

dispersal corridors among core areas of 

the contiguous United States, and the 

effective population size in the 

contiguous United States. Nevertheless, 

the best available information suggests 

that habitat loss as a result of climate 

change, and the resulting exacerbating 

effect on other stressors, is likely to 

decrease the viability of wolverines in 

the contiguous United States over the 

next century. 

We note that, by using the SSA 

framework to guide our analysis of the 

scientific information documented in 

the wolverine SSA report and SSA 

report addendum, we have analyzed the 

cumulative effects of identified threats 

and conservation actions on the DPS. To 

assess the current and future condition 

of the DPS, we evaluate the effects of all 

the relevant factors that may be 

influencing the DPS, including threats 

and conservation efforts. Because the 

SSA framework considers not just the 

presence of the factors, but to what 

degree they collectively influence risk to 

the entire DPS, our assessment 

integrates the cumulative effects of the 

factors and replaces a standalone 

cumulative effects analysis. 

Determination of North American 

Wolverine’s Status 

Section 4 of the Act (16 U.S.C. 1533) 

and its implementing regulations (50 

CFR part 424) set forth the procedures 

for determining whether a species meets 

the definition of an endangered species 

or a threatened species. The Act defines 

an ‘‘endangered species’’ as a species in 

danger of extinction throughout all or a 

significant portion of its range, and a 

‘‘threatened species’’ as a species likely 

to become an endangered species within 

the foreseeable future throughout all or 

a significant portion of its range. The 

Act requires that we determine whether 

a species meets the definition of 

endangered species or threatened 

species because of any of the following 

factors: (A) The present or threatened 

destruction, modification, or 

curtailment of its habitat or range; (B) 

overutilization for commercial, 

recreational, scientific, or educational 

purposes; (C) disease or predation; (D) 

the inadequacy of existing regulatory 

mechanisms; or (E) other natural or 

manmade factors affecting its continued 

existence. 


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Status Throughout All of Its Range 

In our 2018 SSA and October 13, 

2020, withdrawal document (85 FR 

64618), we noted that during the late 

1800s and early 1900s, the wolverine 

population declined or was extirpated 

in much of the contiguous United 

States. This decline and range 

contraction has been attributed to 

unregulated trapping and habitat 

degradation (Hash 1987, p. 583). 

However, given the high-elevation core 

habitats of wolverines in the contiguous 

United States, direct mortality through 

predator poisoning campaigns and 

unregulated trapping were likely the 

primary culprits. 

We have carefully assessed the best 

scientific and commercial information 

available regarding the past, present, 

and future threats to North American 

wolverines in the contiguous United 

States including climate change (Factors 

A and E); effects from roads (Factors A 

and E); disturbance due to winter 

recreational activity (Factors A and E); 

other human disturbance (Factors A and 

E); effects from wildland fire (Factor A); 

disease (Factor C); predation (Factor C); 

overutilization (trapping) (Factor B); 

genetic diversity (Factor E); and small 

population effects (Factor E). We also 

assessed the adequacy of existing 

regulatory mechanisms (Factor D). 

After evaluating threats that may be 

currently affecting wolverines in the 

contiguous United States, we have 

determined that although these threats 

may affect individual wolverines, there 

are no threats currently impacting 

wolverines in the contiguous United 

States at a population level. In the 

future, the synergistic effect of some 

threats coupled with the impacts of 

climate change (increased temperatures 

and decreased spring snowpack) are 

expected to reduce resiliency of the 

contiguous U.S. population, although 

climate change is not currently 

impacting wolverines occurring in the 

United States. Currently, the contiguous 

U.S. population appears resilient, as 

wolverines continue to consistently 

occupy a large portion of the available 

habitat in the western United States. 

Furthermore, wolverine breeding 

populations in the western United 

States are currently distributed across 

four ecoregions, which affords the DPS 

redundancy against catastrophic events. 

This ecoregion variation influences 

representation by potentially providing 

evolutionary potential to adapt to 

changes in the biological and physical 

environment. Thus, wolverines in the 

contiguous United States are not 

currently in danger of extinction 

throughout their range. 

We expect wolverine populations in 

the contiguous United States to decrease 

in resiliency, redundancy, and 

representation within the foreseeable 

future. We consider 2100 to be the 

foreseeable future in this case. The main 

threat to wolverines is the effect of 

climate change on spring snow. We 

were able to reliably model changes in 

spring snow out to 2100 in our climate 

change analysis, and we are able to 

reasonably determine the wolverine’s 

response to this threat is likely in the 

foreseeable future. Wolverine 

populations in the contiguous United 

States are small, fragmented, and 

relatively isolated from larger 

populations in Canada (Cegelski et al. 

2006, pp. 206–207, 210; Sawaya et al. 

2023, entire). Although male-mediated 

dispersal shows some level of wolverine 

population connectivity between the 

United States and Canada along the 

Rocky Mountains, female wolverines 

appear to have virtually no recent 

population connectivity based on recent 

genetic analyses (Sawaya et al. 2023, pp. 

12–14, 17). Small, isolated populations 

are more vulnerable to extinction 

through interactions between 

environmental, genetic, and 

demographic factors (Caughley 1994, 

pp. 221–227). Stochasticity in 

demographic rates at small population 

sizes causes outsized impacts to vital 

rates, even in a constant environment, 

which can greatly increase extinction 

risk. Small, isolated populations also 

lose genetic diversity over time, 

primarily through inbreeding and 

genetic drift, which can exacerbate 

extinction risk if demographic rates are 

further degraded through inbreeding 

depression (Benson et al. 2016, p. 8). 

Low genetic diversity can also reduce 

adaptive capacity and evolutionary 

potential. 

Although historical North American 

wolverine populations were likely 

naturally small and distributed among 

patches of high-elevation alpine habitats 

in the contiguous United States, core 

wolverine habitats in the United States 

are projected to become smaller and 

more fragmented in the future as the 

result of climate change and human 

disturbance. These changes are expected 

to degrade wolverine resiliency and 

redundancy over time, although there 

are uncertainties in the precise amount 

of degradation, how much this 

degradation will affect wolverine 

viability in the contiguous United 

States, and the precise time period over 

which the degradation would happen. 

Despite these uncertainties, the best 

available information indicates the 

impacts are such that the DPS’s viability 

will decrease within the foreseeable 

future. Although wolverines are 

currently distributed across several 

ecological regions of the U.S. West, the 

core attributes related to their adaptive 

capacity may limit the ability of this 

DPS to adapt and persist in the face of 

projected environmental change. Longdistance dispersal and recolonization of 

some of the larger areas outside of the 

current breeding range of North 

American wolverines (e.g., Sierra 

Nevada and central Rocky Mountains) 

could partially mitigate their 

susceptibility to environmental change. 

However, natural dispersal between 

currently occupied core habitats is 

expected to become more difficult in the 

future with anticipated increases in 

human development between the alpine 

core areas and increased backcountry 

winter recreation in core habitats. 

After evaluating threats to the DPS 

and assessing the cumulative effect of 

the threats under the Act’s section 

4(a)(1) factors, we find that wolverine 

populations in the contiguous United 

States are less secure in the future than 

we described in our 2018 SSA and 

October 13, 2020, withdrawal document 

(85 FR 64618). The best available 

information suggests that habitat loss as 

a result of climate change and impacts 

from other stressors are likely to 

negatively impact the viability of 

wolverines in the contiguous United 

States over the next century. Thus, after 

assessing the best available information, 

we conclude that the contiguous U.S. 

DPS of North American wolverine in is 

not currently in danger of extinction but 

is likely to become in danger of 

extinction within the foreseeable future 

throughout all of its range. 

Status Throughout a Significant Portion 

of Its Range 

Under the Act and our implementing 

regulations, a species may warrant 

listing if it is in danger of extinction or 

likely to become so within the 

foreseeable future throughout all or a 

significant portion of its range. The 

court in Center for Biological Diversity 

v. Everson, 435 F. Supp. 3d 69 (D.D.C. 

2020) (Everson), vacated the provision 

of the Final Policy on Interpretation of 

the Phrase ‘‘Significant Portion of Its 

Range’’ in the Endangered Species Act’s 

Definitions of ‘‘Endangered Species’’ 

and ‘‘Threatened Species’’ (Final Policy; 

79 FR 37578; July 1, 2014) that provided 

if the Service determines that a species 

is threatened throughout all of its range, 

the Service will not analyze whether the 

species is endangered in a significant 

portion of its range. 

Therefore, we proceed to evaluating 

whether the species is endangered in a 


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significant portion of its range—that is, 

whether there is any portion of the 

species’ range for which both (1) the 

portion is significant; and (2) the species 

is in danger of extinction in that 

portion. Depending on the case, it might 

be more efficient for us to address the 

‘‘significance’’ question or the ‘‘status’’ 

question first. We can choose to address 

either question first. Regardless of 

which question we address first, if we 

reach a negative answer with respect to 

the first question that we address, we do 

not need to evaluate the other question 

for that portion of the species’ range. 

Following the court’s holding in 

Everson, we now consider whether there 

are any significant portions of the North 

American wolverine’s range in the 

contiguous United States where the DPS 

is in danger of extinction now (i.e., 

endangered). In undertaking this 

analysis for the DPS, we choose to 

address the status question first—we 

consider information pertaining to the 

geographic distribution of both the DPS 

and the threats that the DPS faces to 

identify portions of the range where the 

DPS may be endangered. 

We evaluated the range of the 

contiguous U.S. DPS of North American 

wolverine to determine if the DPS is in 

danger of extinction now in any portion 

of its range. The range can theoretically 

be divided into portions in an infinite 

number of ways. We focused our 

analysis on portions of the range that 

may meet the Act’s definition of an 

endangered species. For this DPS, we 

considered whether the threats or their 

effects on the DPS are greater in any 

biologically meaningful portion of the 

range than in other portions such that 

the DPS is in danger of extinction now 

in that portion. 

We examined the following threats: 

climate change (Factors A and E); effects 

from roads (Factors A and E); 

disturbance due to winter recreational 

activity (Factors A and E); other human 

disturbance (Factors A and E); effects 

from wildland fire (Factor A); disease 

(Factor C); predation (Factor C); 

overutilization (trapping) (Factor B); 

genetic diversity (Factor E); and small 

population effects (Factor E), including 

cumulative effects. 

The North Cascades portion of the 

DPS’s range is the only biologically 

meaningful portion that we identified 

that could potentially have a different 

status than the remainder of the range. 

It is largely isolated by an expanse of 

unsuitable habitat from the larger Rocky 

Mountains portion of the range. All of 

the threats affecting wolverines are 

ubiquitous throughout the contiguous 

U.S. range; however, the low genetic 

diversity of the Cascades population 

could potentially affect this portion 

more so than the rest of the range due 

to the apparent lack of recent genetic 

connectivity with Canada in that 

portion (Sawaya 2023, pers. comm.). 

The North Cascades wolverines are 

isolated from other wolverine 

populations in the United States and 

Canada and likely went through a 

genetic bottleneck with few founders 

(Sawaya 2023, pers. comm.). The 

effective population size of the North 

Cascades population is estimated at Ne

= 4, and the population may be 

vulnerable to inbreeding and loss of 

genetic diversity when considered in 

isolation. Recent genetic research shows 

the population has low heterozygosity 

(less than 0.5) and may be experiencing 

some level of inbreeding (Sawaya 2023, 

pers. comm.). However, there is 

currently no indication that individuals 

or population dynamics are being 

negatively affected by inbreeding 

depression (Sawaya 2023, pers. comm.) 

or that wolverines in this portion are 

currently being more severely or 

differently affected by any other threats. 

Gene flow with wolverines in Canada in 

the future is important to the long-term 

genetic health of the North Cascades 

population, but this portion is not 

currently in danger of extinction, as the 

population is currently showing 

stability in occupancy and not 

expressing any deleterious effects of 

inbreeding. 

We found no biologically meaningful 

portion of the DPS’s range where threats 

are impacting individuals differently 

from how they are affecting the DPS 

elsewhere in the range, or where the 

biological condition of the DPS differs 

from its condition elsewhere in the 

range such that the status of the DPS in 

that portion differs from any other 

portion of the DPS’s range. 

Therefore, no portion of the DPS’s 

range provides a basis for determining 

that the DPS is in danger of extinction 

in a significant portion of its range, and 

we determine that the DPS is likely to 

become in danger of extinction within 

the foreseeable future throughout all of 

its range. This does not conflict with the 

courts’ holdings in Desert Survivors v. 

U.S. Department of the Interior, 321 F. 

Supp. 3d 1011, 1070–74 (N.D. Cal. 2018) 

and Center for Biological Diversity v. 

Jewell, 248 F. Supp. 3d 946, 959 (D. 

Ariz. 2017) because, in reaching this 

conclusion, we did not apply the 

aspects of the Final Policy, including 

the definition of ‘‘significant’’ that those 

court decisions held to be invalid. 

Determination of Status 

Our review of the best scientific and 

commercial data available indicates that 

the contiguous U.S. DPS of the North 

American wolverine meets the Act’s 

definition of a threatened species. 

Therefore, we are listing that DPS as a 

threatened species in accordance with 

sections 3(20) and 4(a)(1) of the Act. 

Available Conservation Measures 

Conservation measures provided to 

species listed as endangered or 

threatened species under the Act 

include recognition as a listed species, 

planning and implementation of 

recovery actions, requirements for 

Federal protection, and prohibitions 

against certain practices. Recognition 

through listing results in public 

awareness, and conservation by Federal, 

State, Tribal, and local agencies, private 

organizations, and individuals. The Act 

encourages cooperation with the States 

and other countries and calls for 

recovery actions to be carried out for 

listed species. The protection required 

by Federal agencies, including the 

Service, and the prohibitions against 

certain activities are discussed, in part, 

below. 

The primary purpose of the Act is the 

conservation of endangered and 

threatened species and the ecosystems 

upon which they depend. The ultimate 

goal of such conservation efforts is the 

recovery of these listed species, so that 

they no longer need the protective 

measures of the Act. Section 4(f) of the 

Act calls for the Service to develop and 

implement recovery plans for the 

conservation of endangered and 

threatened species. The goal of this 

process is to restore listed species to a 

point where they are secure, selfsustaining, and functioning components 

of their ecosystems. 

The recovery planning process begins 

with development of a recovery outline 

made available to the public soon after 

a final listing determination. The 

recovery outline guides the immediate 

implementation of urgent recovery 

actions while a recovery plan is being 

developed. Recovery teams (composed 

of species experts, Federal and State 

agencies, nongovernmental 

organizations, and stakeholders) may be 

established to develop and implement 

recovery plans. The recovery planning 

process involves the identification of 

actions that are necessary to halt and 

reverse the species’ decline by 

addressing the threats to its survival and 

recovery. The recovery plan identifies 

recovery criteria for review of when a 

species may be ready for reclassification 

from endangered to threatened 

(‘‘downlisting’’) or removal from 

protected status (‘‘delisting’’), and 

methods for monitoring recovery 

progress. Recovery plans also establish 


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a framework for agencies to coordinate 

their recovery efforts and provide 

estimates of the cost of implementing 

recovery tasks. Revisions of the plan 

may be done to address continuing or 

new threats to the species, as new 

substantive information becomes 

available. The recovery outline, draft 

recovery plan, final recovery plan, and 

any revisions will be available on our 

website as they are completed (https:// 

www.fws.gov/program/endangeredspecies), or from our Ecological Services 

Program, Pacific Region (see FOR

FURTHER INFORMATION CONTACT). 

Implementation of recovery actions 

generally requires the participation of a 

broad range of partners, including other 

Federal agencies, States, Tribes, 

nongovernmental organizations, 

businesses, and private landowners. 

Examples of recovery actions include 

habitat restoration (e.g., restoration of 

native vegetation), research, captive 

propagation and reintroduction, and 

outreach and education. The recovery of 

many listed species cannot be 

accomplished solely on Federal lands 

because their range may occur primarily 

or solely on non-Federal lands. To 

achieve recovery of these species 

requires cooperative conservation efforts 

on private, State, and Tribal lands. 

Once this DPS is listed, funding for 

recovery actions will be available from 

a variety of sources, including Federal 

budgets, State programs, and cost-share 

grants for non-Federal landowners, the 

academic community, and 

nongovernmental organizations. In 

addition, pursuant to section 6 of the 

Act, the States of California, Colorado, 

Idaho, Montana, Oregon, Utah, 

Washington, and Wyoming will be 

eligible for Federal funds to implement 

management actions that promote the 

protection or recovery of the North 

American wolverine. Information on our 

grant programs that are available to aid 

species recovery can be found at: 

https://www.fws.gov/service/financialassistance. 

Please let us know if you are 

interested in participating in recovery 

efforts for the contiguous U.S. DPS of 

the North American wolverine. 

Additionally, we invite you to submit 

any new information on this DPS 

whenever it becomes available and any 

information you may have for recovery 

planning purposes (see FOR FURTHER

INFORMATION CONTACT). 

Section 7 of the Act is titled, 

‘‘Interagency Cooperation,’’ and it 

mandates all Federal action agencies to 

use their existing authorities to further 

the conservation purposes of the Act 

and to ensure that their actions are not 

likely to jeopardize the continued 

existence of listed species or adversely 

modify critical habitat. Regulations 

implementing section 7 are codified at 

50 CFR part 402. 

Section 7(a)(2) states that each Federal 

action agency shall, in consultation with 

the Secretary, ensure that any action 

they authorize, fund, or carry out is not 

likely to jeopardize the continued 

existence of a listed species or result in 

the destruction or adverse modification 

of designated critical habitat. Each 

Federal agency shall review its action at 

the earliest possible time to determine 

whether it may affect listed species or 

critical habitat. If a determination is 

made that the action may affect listed 

species or critical habitat, formal 

consultation is required (see 50 CFR 

402.14(a)), unless the Service concurs in 

writing that the action is not likely to 

adversely affect listed species or critical 

habitat. At the end of a formal 

consultation, the Service issues a 

biological opinion, containing its 

determination of whether the Federal 

action is likely to result in jeopardy or 

adverse modification. 

Examples of discretionary actions for 

the contiguous U.S. DPS of the North 

American wolverine that may be subject 

to consultation procedures under 

section 7 are land management or other 

landscape-altering activities on Federal 

lands administered by the U.S. Forest 

Service, National Park Service, and 

Bureau of Land Management, as well as 

actions on State, Tribal, local, or private 

lands that require a Federal permit 

(such as a permit from the U.S. Army 

Corps of Engineers under section 404 of 

the Clean Water Act (33 U.S.C. 1251 et 

seq.) or a permit from the Service under 

section 10 of the Act) or that involve 

some other Federal action (such as 

funding from the Federal Highway 

Administration, Federal Aviation 

Administration, or Federal Emergency 

Management Agency). Federal actions 

not affecting listed species or critical 

habitat—and actions on State, Tribal, 

local, or private lands that are not 

federally funded, authorized, or carried 

out by a Federal agency—do not require 

section 7 consultation. Federal agencies 

should coordinate with the local Service 

Field Office (see FOR FURTHER

INFORMATION CONTACT) with any specific 

questions on section 7 consultation and 

conference requirements. 

It is the policy of the Service, as 

published in the Federal Register on 

July 1, 1994 (59 FR 34272), to identify 

to the extent known at the time a 

species is listed, specific activities that 

will not be considered likely to result in 

violation of section 9 of the Act. To the 

extent possible, activities that will be 

considered likely to result in violation 

will also be identified in as specific a 

manner as possible. The intent of this 

policy is to increase public awareness of 

the effect of a listing on proposed and 

ongoing activities within the range of 

the species. Although most of the 

prohibitions in section 9 of the Act 

apply to endangered species, sections 

9(a)(1)(G) and 9(a)(2)(E) of the Act 

prohibit the violation of any regulation, 

including any regulation issued under 

section 4(d) of the Act, pertaining to any 

threatened species of fish or wildlife, or 

threatened species of plant, 

respectively. Section 4(d) of the Act 

directs the Secretary to promulgate 

protective regulations that are necessary 

and advisable for the conservation of 

threatened species. As a result, we 

interpret our policy to mean that, when 

we list a species as a threatened species, 

to the extent possible, we identify 

activities that will or will not be 

considered likely to result in violation 

of the protective regulations under 

section 4(d) for that species. 

The following activities could 

potentially result in a violation of 

section 9 of the Act; this list is not 

comprehensive: Unauthorized 

collecting, handling, possessing, selling, 

delivering, carrying, or transporting of 

the listed subspecies, including import 

or export across State lines and 

international boundaries, except for 

properly documented antique 

specimens of these taxa at least 100 

years old, as defined by section 10(h)(1) 

of the Act. 

Questions regarding whether specific 

activities will constitute violation of 

section 9 of the Act should be directed 

to the Service’s Pacific Regional Office 

(see FOR FURTHER INFORMATION CONTACT). 

II. Interim Rule Issued Under Section 

4(d) of the Act 

Background 

Section 4(d) of the Act contains two 

sentences. The first sentence states that 

the Secretary shall issue such 

regulations as she deems necessary and 

advisable to provide for the 

conservation of species listed as 

threatened species. The U.S. Supreme 

Court has noted that statutory language 

similar to the language in section 4(d) of 

the Act authorizing the Secretary to take 

action that she ‘‘deems necessary and 

advisable’’ affords a large degree of 

deference to the agency (see Webster v. 

Doe, 486 U.S. 592, 600 (1988)). 

Conservation is defined in the Act to 

mean the use of all methods and 

procedures which are necessary to bring 

any endangered species or threatened 

species to the point at which the 

measures provided pursuant to the Act 


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are no longer necessary. Additionally, 

the second sentence of section 4(d) of 

the Act states that the Secretary may by 

regulation prohibit with respect to any 

threatened species any act prohibited 

under section 9(a)(1), in the case of fish 

or wildlife, or section 9(a)(2), in the case 

of plants. Thus, the combination of the 

two sentences of section 4(d) provides 

the Secretary with wide latitude of 

discretion to select and promulgate 

appropriate regulations tailored to the 

specific conservation needs of the 

threatened species. The second sentence 

grants particularly broad discretion to 

the Service when adopting one or more 

of the prohibitions under section 9. 

The courts have recognized the extent 

of the Secretary’s discretion under this 

standard to develop rules that are 

appropriate for the conservation of a 

species. For example, courts have 

upheld, as a valid exercise of agency 

authority, rules developed under section 

4(d) that included limited prohibitions 

against takings (see Alsea Valley 

Alliance v. Lautenbacher, 2007 WL 

2344927 (D. Or. 2007); Washington 

Environmental Council v. National 

Marine Fisheries Service, 2002 WL 

511479 (W.D. Wash. 2002)). Courts have 

also upheld 4(d) rules that do not 

address all of the threats a species faces 

(see State of Louisiana v. Verity, 853 

F.2d 322 (5th Cir. 1988)). As noted in 

the legislative history when the Act was 

initially enacted, ‘‘once an animal is on 

the threatened list, the Secretary has an 

almost infinite number of options 

available to [her] with regard to the 

permitted activities for those species. 

[She] may, for example, permit taking, 

but not importation of such species, or 

[s]he may choose to forbid both taking 

and importation but allow the 

transportation of such species’’ (H.R. 

Rep. No. 412, 93rd Cong., 1st Sess. 

1973). 

The provisions of this 4(d) rule will 

promote conservation of the contiguous 

U.S. DPS of the North American 

wolverine by encouraging management 

of the landscape in ways that meet the 

conservation needs of the wolverine. 

The provisions of this rule are one of 

many tools that we will use to promote 

the conservation of the DPS. 

As mentioned previously in Available 

Conservation Measures, section 7(a)(2) 

of the Act requires Federal agencies, 

including the Service, to ensure that any 

action they authorize, fund, or carry out 

is not likely to jeopardize the continued 

existence of any endangered species or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat of such 

species. 

These requirements are the same for 

a threatened species with a speciesspecific 4(d) rule. For example, as with 

an endangered species, if a Federal 

agency determines that an action is ‘‘not 

likely to adversely affect’’ a threatened 

species that has a species-specific 4(d) 

rule, the agency will still need to 

informally consult with the Service and 

obtain the Service’s written concurrence 

(50 CFR 402.13(c)). Similarly, if a 

Federal agency determines that an 

action is ‘‘likely to adversely affect’’ a 

threatened species, the action will 

require formal consultation and the 

formulation of a biological opinion (50 

CFR 402.14(a)). The Service will take 

into account the exceptions of any 4(d) 

rule when issuing a biological opinion 

and any associated incidental take 

statement, but a 4(d) rule does not 

eliminate the Federal agency’s 

obligation to consult under section 

7(a)(2) of the Act. 

We proposed a 4(d) rule along with 

our proposed listing rule for the 

contiguous U.S. DPS of the wolverine in 

2013 (78 FR 7864; February 4, 2013). In 

the proposed 4(d) rule, we stated that 

we would prohibit take of any 

wolverine in the contiguous United 

States when associated with or related 

to trapping, hunting, shooting, 

collection, capturing, pursuing, 

wounding, killing, and trade. We further 

stated that, in this context, any activity 

where wolverines are attempted to be, 

or are intended to be, trapped, hunted, 

shot, captured, or collected, in the 

contiguous United States, would be 

prohibited. Additionally, we said that it 

would also be prohibited to incidentally 

trap, hunt, shoot, capture, pursue, or 

collect wolverines in the course of 

otherwise legal activities. We also 

clarified that all otherwise legal 

activities involving wolverines and their 

habitat that are conducted in accordance 

with applicable State, Federal, Tribal, 

and local laws and regulations would 

not be considered to be take under the 

proposed 4(d) rule. We identified 

several risk factors for the U.S. DPS of 

the wolverine that, in concert with 

climate change, may result in reduced 

habitat value for the DPS. These risk 

factors included human activities like 

dispersed recreation, land management 

activities by Federal agencies and 

private landowners, and infrastructure 

development. However, in 2013, we 

considered these risk factors to be small 

in scope and scale, and ultimately not 

a concern for the conservation of the 

DPS. As a result, we did not propose to 

prohibit take associated with these 

activities. 

New information on the threats to this 

DPS and how these threats may affect 

the future condition of wolverines in the 

contiguous United States (see Summary 

of Biological Status and Threats, above) 

has changed our understanding of what 

provisions are appropriate for the 

contiguous U.S. DPS of the North 

American wolverine. We are now 

tailoring the provisions of this interim 

4(d) rule informed by new information. 

This is an interim rule, meaning that it 

will go into effect on the effective date 

specified above under DATES, but we are 

also accepting public comments on the 

4(d) rule (see DATES and ADDRESSES, 

above). We will assess any comments 

we receive on the 4(d) rule and publish 

either an affirmation of this interim rule 

or a revised final rule for the 4(d) rule. 

Provisions of the Interim 4(d) Rule 

Exercising the Secretary’s authority 

under section 4(d) of the Act, we have 

developed a rule that is designed to 

address the contiguous U.S. DPS of the 

North American wolverine’s 

conservation needs. As discussed 

previously in Summary of Biological 

Status and Threats, we have concluded 

that the DPS is likely to become in 

danger of extinction within the 

foreseeable future primarily due to 

habitat loss as a result of climate change 

and the cumulative impacts of other, 

lower-level stressors, including winter 

recreation, development, and major 

roads. Section 4(d) requires the 

Secretary to issue such regulations as 

she deems necessary and advisable to 

provide for the conservation of each 

threatened species and authorizes the 

Secretary to include among those 

protective regulations any of the 

prohibitions that section 9(a)(1) of the 

Act prescribes for endangered species. 

We find that the protections, 

prohibitions, and exceptions in this 4(d) 

rule as a whole satisfy the requirement 

in section 4(d) of the Act to issue 

regulations deemed necessary and 

advisable to provide for the 

conservation of the DPS. 

The protective regulations for the 

contiguous U.S. DPS of the North 

American wolverine incorporate 

prohibitions from section 9(a)(1) to 

address the threats to the DPS. Section 

9(a)(1) prohibits the following activities 

for endangered wildlife: importing or 

exporting; take; possession and other 

acts with unlawfully taken specimens; 

delivering, receiving, carrying, 

transporting, or shipping in interstate or 

foreign commerce in the course of 

commercial activity; or selling or 

offering for sale in interstate or foreign 

commerce. This interim 4(d) rule 

includes all of these prohibitions, with 

limited exceptions, for the DPS. With 

these general protective prohibitions in 


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place, the 4(d) rule reinforces the 

preservation of the DPS’s populations 

by prohibiting activities that would 

incentivize the killing of wolverines for 

commercial gain. 

As noted, this 4(d) rule generally 

prohibits the ‘‘take’’ of wolverines in the 

DPS. Under the Act, ‘‘take’’ means to 

harass, harm, pursue, hunt, shoot, 

wound, kill, trap, capture, or collect, or 

to attempt to engage in any such 

conduct. Some of these provisions have 

been further defined in regulation at 50 

CFR 17.3. Take can result knowingly or 

otherwise, by direct and indirect 

impacts, intentionally or incidentally. 

Regulating take will help preserve the 

DPS’s remaining populations and 

decrease the effects to wolverines from 

the synergistic, negative effects from 

other ongoing or future threats. 

Therefore, we are prohibiting take of 

wolverines in the DPS, except for take 

resulting from those actions and 

activities specifically excepted by the 

4(d) rule. 

Exceptions to the prohibition on take 

include all of the general exceptions to 

the prohibition on take of endangered 

wildlife, as set forth in 50 CFR 17.21(c) 

and (d), and additional exceptions, as 

described below. 

The interim 4(d) rule also provides for 

the conservation of the DPS by 

establishing exceptions to the general 

prohibition against ‘‘take’’ of wolverines 

in the DPS in support of conservation 

actions and otherwise lawful activities 

that could incidentally take a wolverine 

but at minimal levels not likely to have 

a negative impact on the DPS’s 

conservation. We considered a variety of 

exceptions and determined that not all 

were necessary (e.g., we do not include 

an exception for take of depredating 

wolverines because wolverines rarely 

take livestock) or would provide 

conservation benefits (e.g., we do not 

include exceptions for backcountry 

winter recreation because recreating in 

these areas can be detrimental to 

wolverines). The exceptions to these 

prohibitions, described in further detail 

below, include certain standard 

exceptions, as well as purposeful take 

due to scientific research on wolverines, 

take incidental to forest management 

activities for the purposes of reducing 

the risk or severity of wildfire, and take 

incidental to legal trapping of species 

other than the wolverine that is 

conducted consistent with State 

trapping laws and regulations and that 

contains steps to minimize the potential 

for capture of wolverines. 

Nothing in this interim 4(d) rule will 

change in any way the recovery 

planning provisions of section 4(f) of the 

Act, the consultation requirements 

under section 7 of the Act, or the ability 

of the Service to enter into partnerships 

for the management and protection of 

the wolverine. However, interagency 

cooperation may be further streamlined 

through planned programmatic 

consultations for the species between 

Federal agencies and the Service. 

Standard Exceptions 

We may, under certain circumstances, 

issue permits to carry out one or more 

of the otherwise prohibited activities. 

These include permits issued for the 

following purposes: for scientific 

research and conservation purposes (for 

an activity that would not fall within 

the research exception for incidental 

take in the 4(d) rule, as described 

below); to enhance propagation or 

survival; for economic hardship; for 

zoological exhibition; for educational 

purposes; for incidental taking (for an 

activity not already excepted in the 4(d) 

rule); or for special purposes consistent 

with the purposes of the Act (see 50 

CFR 17.32). The Act also contains 

certain exemptions from the 

prohibitions, which are found in 

sections 9 and 10 of the Act. 

We recognize the special and unique 

relationship with our State natural 

resource agency partners in contributing 

to conservation of listed species. State 

agencies often possess scientific data 

and valuable expertise on the status and 

distribution of endangered, threatened, 

and candidate species of wildlife and 

plants. State agencies, because of their 

authorities and their close working 

relationships with local governments 

and landowners, are in a unique 

position to assist us in implementing all 

aspects of the Act. In this regard, section 

6 of the Act provides that we cooperate 

to the maximum extent practicable with 

the States in carrying out programs 

authorized by the Act. Therefore, any 

qualified employee or agent of a State 

conservation agency that is a party to a 

cooperative agreement with us in 

accordance with section 6(c) of the Act, 

who is designated by his or her agency 

for such purposes, will be able to 

conduct activities designed to conserve 

the contiguous U.S. DPS of the North 

American wolverine that may result in 

otherwise prohibited take without 

additional authorization. 

Scientific Research 

Future scientific research on North 

American wolverines in the contiguous 

United States will aid conservation and 

recovery by leading to a better 

understanding of the biology and 

ecology of this elusive and hard-tostudy species. WAFWA, in coordination 

with Tribal partners, formed a multiState, multi-agency working group 

(Western States Wolverine Working 

Group) to design and implement the 

Western States Wolverine Conservation 

Project (WSWCP)–Coordinated 

Occupancy Survey (Service 2018, p. 52). 

The primary objectives of the WSWCP 

include: (1) implement a monitoring 

program to define a baseline wolverine 

distribution and genetic characteristics 

of the metapopulation across Montana, 

Idaho, Wyoming, and Washington; (2) 

model and maintain the connectivity of 

the wolverine metapopulation in the 

western United States; and (3) develop 

policies to address socio-political needs 

to assist wolverine population 

expansion as a conservation tool, 

including translocation of wolverines 

(Service 2018, p. 52). Activities 

associated with scientific research may 

include capture, anesthesia, collaring, 

tracking, genetic sampling, the use and 

baiting of camera and DNA traps, den 

monitoring, and aerial surveying. State 

agencies with approved cooperative 

agreements (see cooperative agreements 

discussion above for additional 

information) and the Service will not be 

required to obtain separate ESA permits 

for take associated with these actions, as 

we are including the exceptions at 50 

CFR 17.31(b) in the 4(d) rule. To 

facilitate Federal agencies or federally 

recognized Tribes to participate in and 

assist with these activities, we are also 

including an exception that allows 

biologists, acting in an official capacity, 

from other Federal agencies or federally 

recognized Tribes to take wolverine for 

scientific or research purposes that are 

associated with wolverine conservation 

efforts, as identified by the Service, 

provided such taking does not result in 

death or permanent injury to the 

wolverine(s) involved. Taking that 

results in death or permanent injury 

must be reported to the appropriate U.S. 

Fish and Wildlife Service law 

enforcement office and to appropriate 

State and Tribal authorities. 

Forest Management Activities for the 

Purposes of Reducing the Risk or 

Severity of Wildfire 

As discussed in the February 4, 2013, 

proposed listing rule (78 FR 7864) and 

October 13, 2020, withdrawal document 

(85 FR 64618), management activities 

(e.g., timber harvest, wildland 

firefighting, prescribed fire, and 

silviculture) can modify wolverine 

habitat, but this generalist species 

appears to be affected little by changes 

to the vegetative characteristics of its 

habitat. In addition, most wolverine 

breeding habitat in the contiguous 

United States occurs at high elevations 

in rugged terrain that is not conducive 


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to intensive forms of silviculture and 

timber harvest. Forest management 

activities for the purposes of reducing 

the risk or severity of wildfire are 

generally not a threat to wolverines in 

the contiguous United States. 

Under this interim 4(d) rule, 

incidental take caused by forest 

vegetation management for the purpose 

of wildfire mitigation that promotes the 

long-term stability and diversity of 

forests will not be prohibited. Broadly, 

the forest vegetation and fire 

management activities referred to above 

may include, but are not limited to, 

silviculture practices and forestmanagement activities that address fuels 

management; insect and disease 

impacts; vegetation management in 

existing utility rights-of-way; and 

wildlife-habitat management, including 

planting seedlings or sowing seeds, 

mechanical cuttings as a restoration tool 

in stands experiencing advancing 

succession, full or partial suppression of 

fires, allowing fires to burn, and survey 

and monitoring of forest health. Because 

no forest vegetation management 

activities for the purposes of reducing 

the risk or severity of wildfire pose any 

threat to the North American wolverine 

at the DPS level, we purposefully do not 

specify in detail what types of these 

activities are included in this exception, 

or how, when, or where they must be 

conducted, as long as they are 

conducted in accordance with 

applicable law; these activities may also 

vary in how they are conducted across 

the DPS’ wide range. Therefore, this 

interim 4(d) rule will facilitate the 

continuation of forest vegetation 

management activities because these 

activities pose no or minimal threats to 

the North American wolverine at the 

DPS level and result in only de minimis 

forms of take. Forest management can 

also contribute to the DPS’s 

conservation into the future by 

maintaining overall forest health in and 

adjacent to wolverine habitat. This 

exception, and any relevant future 

section 7 consultations with Federal 

agencies, also allow for flexibility to 

accommodate specific physical 

conditions, resource needs, and 

constraints across the DPS’s range. 

Incidental Trapping 

Wolverines are occasionally 

incidentally trapped and killed in the 

contiguous United States in the course 

of legal trapping for other species, 

typically wolf trapping. This occurs at 

low levels in a portion of the 

wolverine’s breeding range (mainly 

Idaho and Montana) and does not 

currently represent a stressor to the 

wolverine in the contiguous United 

States at the population or subspecies 

level. Since 2012, there have been 10 

nontarget wolverine captures (average = 

fewer than 1/year) resulting in 3 

mortalities in Montana (MFWP 2023, in 

litt., p. 1). In Idaho, 14 nontarget 

captures (0.7/year) of wolverines have 

occurred during licensed trapping 

activities, with no demonstrable trend 

in capture rates over the past 20 years 

(IDFG 2022, in litt., p. 3). Between 

November 2017 and August 2022, IDFG 

reported that nine wolverines were 

incidentally trapped, with two resulting 

in mortalities (IDFG 2022, in litt., pp. 5, 

16–22). We have no recent reports of 

wolverines incidentally trapped in other 

States within the range during the 

course of legal trapping activities. 

In 2021, in both Idaho and Montana, 

laws and regulations were enacted that 

may increase the amount of wolf 

trapping and the risk of incidental 

trapping of wolverines because of the 

use of snares, extended trapping 

seasons, and financial incentives 

(Service 2023, p. 39). However, because 

wolverines differ from wolves in size, 

distribution, and behavior, and State 

laws and guidelines influence trappers 

to use trap tension, site selection, and 

snare height to reduce the likelihood of 

incidental capture, we expect minimal 

effects. In addition, year-round wolf 

trapping seasons in Idaho are limited to 

private lands, where there is very little 

core wolverine habitat, further reducing 

the potential for incidental taking 

through trapping. 

As discussed above under 

Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes, States within the North 

American wolverine’s range in the 

contiguous United States have enacted 

multiple regulations and 

recommendations to limit incidental 

trapping mortality of wolverines. 

Additionally, the legal trapping that 

occurs for other species, like bobcat and 

marten, does not lend itself to wolverine 

incidental trapping due to the types of 

traps used, placement of those traps, 

and habitat in which they would be 

deployed. We expect incidental 

trapping of wolverines to continue to be 

very limited throughout the DPS’s 

range. 

Incidental trapping mortality of 

wolverines in the contiguous United 

States is minimal and does not impact 

wolverines at a population or species 

level. Mowat et al. (2020, p. 221) 

concluded the maximum sustainable 

harvest rate for wolverines is about 8 

percent. Based on a recent analysis of an 

area in Canada that was experiencing 

population declines related to 

overharvest, Mowat et al. (2020, p. 224) 

recommended reducing direct trapping 

mortality to no more than 4 percent per 

year across their study area to promote 

wolverine population recovery. In the 

contiguous United States, where there is 

no direct trapping, incidental trapping 

rates have been well below this 

recommended rate. If we assume there 

are approximately 300 wolverines in the 

contiguous United States and assume 2 

wolverine mortalities per year from 

incidental trapping (a conservative 

estimate from the incidental trapping 

mortalities we know of since 2012), that 

would be only 0.67 percent of the 

population per year. This minimal level 

of loss will not significantly impact the 

contiguous U.S. population of North 

American wolverines and will not 

inhibit conservation of the DPS. We 

conclude that the overall impact of 

incidental trapping that is conducted in 

accordance with State or Tribal trapping 

laws and regulations and in a manner 

that uses best practices to minimize 

capture and mortality of wolverines, is 

not expected to negatively affect 

conservation and recovery efforts for the 

contiguous U.S. DPS of the North 

American wolverine. Therefore, take 

due to this type of trapping will not be 

prohibited. Take due to trapping that is 

not in compliance with applicable State 

or Tribal laws or regulations and that 

results in the incidental trapping of a 

wolverine is prohibited and subject to 

penalties under section 9 of the Act. 

Any take of wolverine from incidental 

trapping should be reported to the 

nearest U.S. Fish and Wildlife Service 

law enforcement office and to the 

appropriate State wildlife agency or 

Tribal wildlife authorities within 5 days 

of occurrence. Unharmed individuals 

are to be released immediately. 

We anticipate that the additional take 

excepted by this interim 4(d) rule will 

only have a minimal impact on 

wolverine habitat and individuals in the 

contiguous United States. The activities 

associated with scientific research, 

forest management for the purposes of 

reducing the risk or severity of wildfire, 

and legal trapping of other species in a 

manner that reduces risk to wolverines 

are expected to result in low levels of 

take of individuals given the limited 

scope and scale of these activities. 

We conclude that take of wolverines 

excepted by this interim 4(d) rule will 

be small and will not pose a significant 

impact on the conservation of the DPS 

as a whole. However, we recognize that 

there is some uncertainty regarding the 

level of take that may result and that 

there are other approaches and 

additional conservation measures that 

could improve the overall conservation 

outcome of this interim 4(d) rule. We 


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are seeking public comments on this 

interim 4(d) rule (see Public Comments 

Solicited on the Interim 4(d) Rule, 

below), and we will publish either an 

affirmation of this interim rule or a final 

revised rule after we fully consider all 

comments we receive. 

Need for Interim Rule 

We initially proposed a 4(d) rule for 

the wolverine in 2013, in association 

with our proposal to classify the 

wolverine as a threatened species (78 FR 

7864; February 4, 2013). We accepted 

comments on that 2013 proposed 4(d) 

rule and have considered the comments 

we received regarding the proposed 4(d) 

rule in developing this interim 4(d) rule. 

Thus, we engaged in notice-andcomment rulemaking, and we could 

have issued the 4(d) rule as a final rule 

rather than as an interim rule with an 

additional comment period. However, 

we have elected to issue the 4(d) rule as 

an interim rule and to accept public 

comments to ensure a robust 

opportunity for the public to consider 

the prohibitions and exceptions 

prescribed, while providing protections 

for the threatened DPS and complying 

with our court-ordered deadline to 

finalize the listing determination. 

The Service considered segregating 

the 4(d) rule from the listing 

determination and issuing a revised 

proposed rule for notice and comment 

before finalizing the 4(d) rule. However, 

under 5 U.S.C. 553(b)(3)(B) of the 

Administrative Procedure Act (APA), 

we find good cause to proceed without 

reproposing the 4(d) rule and 

undertaking notice and comment before 

finalizing the 4(d) rule. If the Secretary 

were to repropose a 4(d) rule and 

finalize it through the standard 

rulemaking process, we would be 

unable to finalize the protective 

regulations set forth in this interim 4(d) 

rule concurrently with the final listing 

rule for the DPS. This would result in 

no protections for the DPS until we 

complete a process to repropose and 

finalize a 4(d) rule. That outcome would 

be contrary to the public interest in this 

case because immediate implementation 

of the interim 4(d) rule when the 

species’ listing is effective (see DATES, 

above) has the advantage of providing a 

conservation benefit to the North 

America wolverine in the contiguous 

United States. Under this interim 4(d) 

rule, the DPS will be protected by the 

general section 9(a)(1) prohibitions, 

with the aforementioned exceptions. 

Alternatively, another option left to the 

agency’s discretion would be to have no 

prohibitions for a species determined to 

be threatened under the Act. However, 

as stated, we think that it is appropriate 

to provide some protection for this DPS 

now so that wolverines in the United 

States have the best chance of surviving 

in the face of climate change impacts 

and other threats. We find that this 

interim 4(d) rule provides appropriate 

protections to promote the conservation 

of the DPS across its range while 

providing the flexibility for certain 

otherwise lawful activities to occur 

without significantly impacting the DPS 

or its habitat. The final rule listing the 

contiguous U.S. DPS of the North 

American wolverine as a threatened 

species under the Act is published as a 

part of this document and is effective on 

the date specified in DATES, above. To 

avoid any confusion arising from 

varying effective dates, and because we 

cannot establish a 4(d) rule for a species 

that is not yet listed, this interim 4(d) 

rule will also be effective on the date 

specified in DATES, above, to coincide 

with the effective date of the listing. 

Public Comments Solicited on the 

Interim 4(d) Rule 

We request comments or information 

from other concerned Federal and State 

agencies, Tribes, the scientific 

community, or any other interested 

party concerning the interim 4(d) rule. 

With regard to the interim 4(d) rule, we 

particularly seek comments regarding: 

(1) Whether the 4(d) rule as a whole 

is necessary and advisable to provide for 

the conservation of the contiguous U.S. 

DPS of the North American wolverine. 

(2) Information concerning the extent 

to which we should include any of the 

section 9 prohibitions in the 4(d) rule. 

(3) Whether we should consider any 

additional exceptions from the 

prohibitions, such as take as a result of 

other categories of activities beyond 

those described, and, if so, under what 

conditions and with what conservation 

measures, if any. 

(4) Additional provisions the Service 

may wish to consider for a revision to 

the interim 4(d) rule in order to 

conserve, recover, and manage the DPS. 

Our determination to affirm or revise 

the interim 4(d) rule will take into 

consideration all written comments and 

any additional information we receive. 

Please note that comments merely 

stating support for or opposition to the 

interim 4(d) rule without providing 

supporting information, although noted, 

will not be considered. Our final 4(d) 

rule may differ from this interim 4(d) 

rule, based on our review of all 

information we receive during this 

rulemaking proceeding. We may change 

the parameters of the prohibitions or the 

exceptions to those prohibitions in the 

4(d) rule if we conclude it is appropriate 

in light of comments and new 

information received. For example, we 

may expand the prohibitions if we 

conclude that the protective regulations, 

including those additional prohibitions, 

are necessary and advisable to provide 

for the conservation of the species. 

Conversely, we may establish additional 

exceptions to the prohibitions in the 

final rule if we conclude that the 

activities would facilitate or are 

compatible with the conservation and 

recovery of the species. 

Our intent is to issue an affirmation 

of this interim 4(d) rule or issue a 

revised 4(d) rule for the contiguous U.S. 

DPS of the North American wolverine 

by December 2024. 

As we state above under DATES, we 

are opening a 60-day public comment 

period on the interim 4(d) rule. You 

may submit your comments and 

materials concerning the interim 4(d) 

rule by one of the methods listed in 

ADDRESSES. We request that you send 

comments only by the methods 

described in ADDRESSES. If you submit 

information via https://

www.regulations.gov, your entire 

submission—including any personal 

identifying information—will be posted 

on the website. 

If your submission is made via a 

hardcopy that includes personal 

identifying information, you may 

request at the top of your document that 

we withhold this information from 

public review. However, we cannot 

guarantee that we will be able to do so. 

We will post all hardcopy submissions 

on https://www.regulations.gov. Please 

include sufficient information with your 

comments to allow us to verify any 

scientific or commercial information 

you include. 

Comments and materials we receive, 

as well as supporting documentation we 

used in preparing this rule, will be 

available for public inspection on 

https://www.regulations.gov, or by 

appointment, during normal business 

hours, at the Pacific Region Ecological 

Services Program (see FOR FURTHER

INFORMATION CONTACT). 

III. Critical Habitat 

Background 

Critical habitat is defined in section 3 

of the Act as: 

(1) The specific areas within the 

geographical area occupied by the 

species, at the time it is listed in 

accordance with the Act, on which are 

found those physical or biological 

features 

(a) Essential to the conservation of the 

species, and 

(b) Which may require special 

management considerations or 

protection; and 


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Federal Register / Vol. 88, No. 229 / Thursday, November 30, 2023 / Rules and Regulations 83771 

(2) Specific areas outside the 

geographical area occupied by the 

species at the time it is listed, upon a 

determination that such areas are 

essential for the conservation of the 

species. 

Critical Habitat Determinability 

Our regulations at 50 CFR 424.12(a)(2) 

state that critical habitat is not 

determinable when one or both of the 

following situations exist: 

(i) Data sufficient to perform required 

analyses are lacking, or 

(ii) The biological needs of the species 

are not sufficiently well known to 

identify any area that meets the 

definition of ‘‘critical habitat.’’ 

When critical habitat is not 

determinable, the Act allows the Service 

an additional year to publish a critical 

habitat designation (16 U.S.C. 

1533(b)(6)(C)(ii)). 

We reviewed the available 

information pertaining to the biological 

needs of the contiguous U.S. DPS of the 

North American wolverine and habitat 

characteristics where the DPS is located. 

A careful assessment of the economic 

impacts that may occur due to a critical 

habitat designation has yet to occur, and 

we will be working to acquire the 

complex information needed to perform 

that assessment. Therefore, due to the 

current lack of data sufficient to perform 

required analyses, we conclude that the 

designation of critical habitat for the 

DPS is not determinable at this time in 

accordance with 50 CFR 424.12(a)(2)(i). 

The Act allows the Service an 

additional year to publish a critical 

habitat designation that is not 

determinable at the time of listing (16 

U.S.C. 1533(b)(6)(C)(ii)). 

Required Determinations 

Clarity of the Rule 

We are required by E.O.s 12866 and 

12988 and by the Presidential 

Memorandum of June 1, 1998, to write 

all rules in plain language. This means 

that each rule we publish must: 

(1) Be logically organized; 

(2) Use the active voice to address 

readers directly; 

(3) Use clear language rather than 

jargon; 

(4) Be divided into short sections and 

sentences; and 

(5) Use lists and tables wherever 

possible. 

If you feel that we have not met these 

requirements, send us comments by one 

of the methods listed in ADDRESSES. To 

better help us revise the rule, your 

comments should be as specific as 

possible. For example, you should tell 

us the numbers of the sections or 

paragraphs that are unclearly written, 

which sections or sentences are too 

long, the sections where you feel lists or 

tables would be useful, etc. 

National Environmental Policy Act (42 

U.S.C. 4321 et seq.) 

Regulations adopted pursuant to 

section 4(a) of the Act are exempt from 

the National Environmental Policy Act 

(NEPA; 42 U.S.C. 4321 et seq.) and do 

not require an environmental analysis 

under NEPA. We published a notice 

outlining our reasons for this 

determination in the Federal Register 

on October 25, 1983 (48 FR 49244). This 

includes listing, delisting, and 

reclassification rules, as well as critical 

habitat designations and speciesspecific protective regulations 

promulgated concurrently with a 

decision to list or reclassify a species as 

threatened. The courts have upheld this 

position (e.g., Douglas County v. 

Babbitt, 48 F.3d 1495 (9th Cir. 1995) 

(critical habitat); Center for Biological 

Diversity v. U.S. Fish and Wildlife 

Service, 2005 WL 2000928 (N.D. Cal. 

Aug. 19, 2005) (concurrent 4(d) rule)). 

Government-to-Government 

Relationship With Tribes 

In accordance with the President’s 

memorandum of April 29, 1994 

(Government-to-Government Relations 

with Native American Tribal 

Governments; 59 FR 22951), E.O. 13175 

(Consultation and Coordination with 

Indian Tribal Governments), and the 

Department of the Interior’s manual at 

512 DM 2, we readily acknowledge our 

responsibility to communicate 

meaningfully with federally recognized 

Tribes on a government-to-government 

basis. In accordance with Secretary’s 

Order 3206 of June 5, 1997 (American 

Indian Tribal Rights, Federal-Tribal 

Trust Responsibilities, and the 

Endangered Species Act), we readily 

acknowledge our responsibilities to 

work directly with Tribes in developing 

programs for healthy ecosystems, to 

acknowledge that Tribal lands are not 

subject to the same controls as Federal 

public lands, to remain sensitive to 

Indian culture, and to make information 

available to Tribes. During the 

development of the wolverine SSA 

report addendum, we asked for 

information and concerns from all the 

federally recognized Tribes in the 

contiguous U.S. range of the North 

American wolverine in California, 

Colorado, Idaho, Montana, Oregon, 

Utah, Washington, and Wyoming. While 

we did not receive any information 

regarding the wolverine from any Tribe 

specific to the SSA report addendum, 

we remain committed to engaging with 

interested Tribes regarding the interim 

4(d) rule, future proposed critical 

habitat designation, and future recovery 

planning for the contiguous U.S. DPS of 

the North American wolverine. 

References Cited 

A complete list of references cited in 

this rulemaking is available on the 

internet at https://www.regulations.gov 

and upon request from the Pacific 

Region Ecological Services Program (see 

FOR FURTHER INFORMATION CONTACT). 

Authors 

The primary authors of this rule are 

the staff members of the Fish and 

Wildlife Service’s Species Assessment 

Team and the Pacific Region Ecological 

Services Program. 

List of Subjects in 50 CFR Part 17 

Endangered and threatened species, 

Exports, Imports, Plants, Reporting and 

recordkeeping requirements, 

Transportation, Wildlife. 

Regulation Promulgation 

Accordingly, we amend part 17, 

subchapter B of chapter I, title 50 of the 

Code of Federal Regulations, as set forth 

below: 

PART 17—ENDANGERED AND 

THREATENED WILDLIFE AND PLANTS 

■ 1. The authority citation for part 17 

continues to read as follows: 

Authority: 16 U.S.C. 1361–1407; 1531– 

1544; and 4201–4245, unless otherwise 

noted. 

■ 2. Amend § 17.11, in paragraph (h), by 

adding an entry for ‘‘Wolverine, North 

American [Contiguous U.S. DPS]’’ to the 

List of Endangered and Threatened 

Wildlife in alphabetical order under 

MAMMALS to read follows: 

§ 17.11 Endangered and threatened 

wildlife. 

* * * * * 

(h) * * * 


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83772 Federal Register / Vol. 88, No. 229 / Thursday, November 30, 2023 / Rules and Regulations 

Common name Scientific name Where listed Status Listing citations and 

applicable rules 

MAMMALS 

* * * * * * * 

Wolverine, North American 

[Contiguous U.S. DPS].

Gulo gulo luscus ............... Where found within the 

contiguous U.S.A.

T 88 FR [INSERT FEDERAL REGISTER 

PAGE WHERE THE DOCUMENT 

BEGINS], 11/30/2023; 50 CFR 

17.40(u).4d

* * * * * * * 

■ 3. Amend § 17.40 by adding paragraph 

(u) to read as follows: 

§ 17.40 Special rules—mammals. 

* * * * * 

(u) North American wolverine (Gulo 

gulo luscus), contiguous U.S. DPS. 

(1) Prohibitions. The following 

prohibitions that apply to endangered 

wildlife also apply to the contiguous 

U.S. distinct population segment (DPS) 

of the North American wolverine. 

Except as provided under paragraph 

(u)(2) of this section and §§ 17.4 and 

17.5, it is unlawful for any person 

subject to the jurisdiction of the United 

States to commit, to attempt to commit, 

to solicit another to commit, or cause to 

be committed, any of the following acts 

in regard to this DPS: 

(i) Import or export, as set forth at 

§ 17.21(b) for endangered wildlife. 

(ii) Take, as set forth at § 17.21(c)(1) 

for endangered wildlife. 

(iii) Possession and other acts with 

unlawfully taken specimens, as set forth 

at § 17.21(d)(1) for endangered wildlife. 

(iv) Interstate or foreign commerce in 

the course of a commercial activity, as 

set forth at § 17.21(e) for endangered 

wildlife. 

(v) Sale or offer for sale, as set forth 

at § 17.21(f) for endangered wildlife. 

(2) Exceptions from prohibitions. In 

regard to this DPS, you may: 

(i) Conduct activities as authorized by 

a permit under § 17.32. 

(ii) Take, as set forth at § 17.21(c)(2) 

through (c)(4) for endangered wildlife. 

(iii) Take, as set forth at § 17.31(b). 

(iv) Possess and engage in other acts 

with unlawfully taken wildlife, as set 

forth at § 17.21(d)(2) for endangered 

wildlife. 

(v) Take caused by scientific or 

research activities for wolverine 

undertaken by a biologist from a Federal 

agency other than the U.S. Fish and 

Wildlife Service, or a federally 

recognized Tribe, when acting in the 

course of their official duties, provided 

that such taking does not result in the 

death or permanent injury to the 

wolverine(s) involved and that the 

taking is reported to the nearest U.S. 

Fish and Wildlife Service law 

enforcement office and to the 

appropriate State wildlife agency or 

Tribal wildlife authorities. Activities 

associated with scientific research may 

include capture, anesthesia, collaring, 

tracking, genetic sampling, the use and 

baiting of camera and DNA traps, den 

monitoring, and aerial surveying. 

(vi) Take incidental to an otherwise 

lawful activity caused by: 

(A) Forest vegetation management 

activities for the purpose of reducing the 

risk or severity of wildfire. 

(B) Trapping of species other than 

wolverine, provided that the trapping is 

conducted in accordance with State or 

Tribal trapping laws and regulations, 

the trapping is conducted in a manner 

that uses best practices to minimize the 

potential for capture and mortality of 

wolverines, and any take of wolverine is 

reported to the nearest U.S. Fish and 

Wildlife Service law enforcement office 

and to the appropriate State wildlife 

agency or Tribal wildlife authorities 

within 5 days of occurrence. Unharmed 

individuals are to be released 

immediately. 

Martha Williams, 

Director, U.S. Fish and Wildlife Service. 

[FR Doc. 2023–26206 Filed 11–29–23; 8:45 am] 

BILLING CODE 4333–15–P 


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