A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

Production services provided by:

Bureau of Land Management

National Operations Center

Information and Publishing Services Section

P.O. Box 25047

Denver, CO 80225

Available online at:

www.blm.gov/nstc/library/techno2.htm

BLM/CO/GI-08/014

Suggested citation:

Holmes, B.E. 2008. A review of black-footed ferret reintroduction in northwest Colorado, 

2001–2006. Technical Note 426. U.S. Department of the Interior, Bureau of Land 

Management, White River Field Office, Colorado. 43 pp. 

Cover photo and all other photos except as noted by:

Brian Holmes, BLM White River Field Office

Photo on page 11 by:

Heather Sauls, BLM White River Field Office
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

Prepared by:

Brian E. Holmes

Wildlife Biologist

Bureau of Land Management

White River Field Office

220 East Market Street

Meeker, Colorado 81641
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A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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THE REINTRODUCTION of black-footed 

ferrets in Colorado has been made possible 

by the dedicated work of many individuals 

from a variety of agencies and organizations. 

In particular, Mike Albee of the Bureau of 

Land Management in Craig, Colorado, and 

Bob Leachman of the U.S. Fish and Wildlife 

Service in Grand Junction, Colorado, had 

the vision and laid the groundwork upon 

which all subsequent work has been based. 

In addition, the following people or groups 

have contributed greatly to the recovery 

of black-footed ferrets in Colorado and, in 

many cases, elsewhere:

ACKNOWLEDGMENTS

Desa Ausmus

Lisa Belmonte

Brent Bibles

Dean Biggins

Gene Byrne

Cross Mountain Ranch

Mike Grode

Ed Hollowed

Mike Lockhart

Al Pfister

Beverly Rave

Lonnie Renner

Pam Schnurr 

Dale Skidmore 

Stacey Smith

Scott Winkler

Wolf Creek Work Group

Lisa Wolfe

Terry Wygant

Bart Zwetzig
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CONTENTS

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

List of Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Cooperating Agencies and Parties . . . . . . . . . . . . . . . . . . . . . . . .2

Program History and Authorization . . . . . . . . . . . . . . . . . . . . . . 3

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Description of the Wolf Creek Management Area . . . . . . . . . . .5

Prairie Dog Management and Monitoring . . . . . . . . . . . . . . . . .6

Disease Management and Monitoring . . . . . . . . . . . . . . . . . . . .8

Black-Footed Ferret Management . . . . . . . . . . . . . . . . . . . . . . 10

 Allocation and Preconditioning . . . . . . . . . . . . . . . . . . . 10

 Releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Monitoring Efforts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Spotlighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 Radio Telemetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

 Working Dogs for Conservation . . . . . . . . . . . . . . . . . . . 16

 Snowtracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Reproduction in the Wild . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Population Size, Survival, and Movements . . . . . . . . . . . . . . .17

Discussion and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Appendix A: Colony-Specific Prairie Dog 

Transect Sampling Summary for the 

Wolf Creek Management Area, 2004–2006 . . . . . . . . . . . . . . . . . . 23

Appendix B: Summary of Black-Footed Ferret 

Release Data from the Wolf Creek 

Management Area, 2001–2006 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
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LIST OF ILLUSTRATIONS

FIGURES

Figure 1. Historic distribution records of black-footed ferrets 

and the range of three prairie dog species in Colorado 

(after Anderson et al. 1986).

Figure 2. Location of the three black-footed ferret 

management areas in northwest Colorado.

Figure 3. Land ownership within the Wolf Creek 

Management Area.

Figure 4. White-tailed prairie dog distribution within the Wolf 

Creek Management Area. Colonies are labeled with 

numbers referred to in the text and in Appendix A.

Figure 5. An example of white-tailed prairie dog and blackfooted ferret habitat within the Wolf Creek Management Area. This is a photograph of part of colony 

20/23, where ferrets were found routinely during 

2005 and 2006. Pinyon Ridge, the eastern boundary of 

the Wolf Creek Management Area, is in the background.

Figure 6. All black-footed ferret release locations within the 

Wolf Creek Management Area, 2002 to 2006 

(2001 data not available).

Figure 7. a) An example of the 6-inch-diameter circular antenna 

of a hand-held passive integrated transponder (PIT) 

reader over the entrance of a prairie dog burrow. b) In 

this picture, the PIT reader is in a storage pouch and 

connected to a 12 V power source.

Figure 8. Total spotlighting survey effort by year in the Wolf 

Creek Management Area, 2002 to 2006. Bars represent 

total effort expended throughout the year, but the 

bulk of survey time occurred in August and September.

Figure 9. All black-footed ferret relocations within the Wolf 

Creek Management Area, 2001 to 2006. Locations in 

green represent 1) captive-born ferrets that survived 

to at least the following spring to enter their first 

breeding season and 2) wild-born ferrets. Locations in 

blue represent ferrets relocated in the year they were 

released that survived at least 30 days in the wild 

following release.

Figure 10. Documented long-distance, intercolony dispersal 

movements by ferrets within the Wolf Creek 

Management Area.
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Figure B-1. Black-footed ferret release locations within the 

Wolf Creek Management Area – 2002.

Figure B-2. Black-footed ferret release locations within the Wolf 

Creek Management Area – 2003.

Figure B-3. Black-footed ferret release locations within the Wolf 

Creek Management Area – 2004.

Figure B-4. Black-footed ferret release locations within the Wolf 

Creek Management Area – 2005.

Figure B-5. Black-footed ferret release locations within the Wolf 

Creek Management Area – 2006.

TABLES

Table 1. White-tailed prairie dog population attributes within 

the Wolf Creek Management Area, 2002 to 2006.

Table 2. Disease surveillance results from coyote serological 

surveys for the Wolf Creek Management Area, 

2000 to 2005. 

Table 3. Summary of black-footed ferrets released within the 

Wolf Creek Management Area, 2001 to 2006.

Table 4. Total number of individual black-footed ferrets 

observed within the Wolf Creek Management Area, 

2001 to 2006.

Table A-1. 2004 Wolf Creek Management Area 

transecting summary.

Table A-2. 2005 Wolf Creek Management Area 

transecting summary.

Table A-3. 2006 Wolf Creek Management Area 

transecting summary.

Table B-1. 2001 Wolf Creek black-footed ferret release data.

Table B-2. 2002 Wolf Creek black-footed ferret release data.

Table B-3. 2003 Wolf Creek black-footed ferret release data.

Table B-4. 2004 Wolf Creek black-footed ferret release data.

Table B-5. 2005 Wolf Creek black-footed ferret release data.

Table B-6. 2006 Wolf Creek black-footed ferret release data.
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ABSTRACT

BETWEEN THE FALL OF 2001 and the end of 

2006, 217 black-footed ferrets (Mustela 

nigripes) were released within the Wolf Creek 

Management Area (WCMA) in northwest 

Colorado in an effort to reestablish this 

species within its former range. Following 

5 years of releases and monitoring, the 

minimum prebreeding (spring) population 

within the WCMA in 2006 was 9 ferrets 

and the minimum population at the end 

of 2006 was 13 ferrets. While survival of 

released captive-raised ferrets was high for 

some colonies in the eastern portion of the 

WCMA, survival throughout much of the 

rest of the area was low compared to other 

ferret reintroduction sites. Three wildborn kits from three separate litters were 

documented, representing a major step in 

the recovery effort. However, the observed 

average litter size of 1.0 was also lower 

than other reintroduction sites and is probably insufficient to maintain the population 

without yearly supplemental releases. 

Overall minimum ferret population size in 

the WCMA increased steadily from 2002 to 

2006, as did the population of their primary 

prey, the white-tailed prairie dog (Cynomys 

leucurus). Observed differences in ferret 

survival and numbers of wild-born kits 

produced in different portions of the WCMA 

appear to be driven primarily by differences 

in habitat quality (the density of prairie 

dogs and their burrows). This reintroduction 

program has contributed valuable information for research and management needs 

pertinent to ferret recovery rangewide, and 

work continues toward the establishment 

of a viable population and recovery of this 

species in Colorado.
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INTRODUCTION

BLACK-FOOTED FERRETS (Mustela nigripes)

are listed as “endangered” under the Endangered Species Act (ESA) and historically 

occurred throughout the grasslands and 

intermountain basins of west-central North 

America where populations of prairie dogs 

(Cynomys spp.) occurred. Once thought 

extinct, a remnant population of ferrets was 

found near Meeteetse, Wyoming, in 1981, 

but this population subsequently declined, 

and the last remaining animals were 

captured to begin a captive-breeding 

program in 1987. Since then, ferrets have 

been reintroduced within their historical 

range at sites in six of the United States 

(Arizona, Colorado, Montana, South Dakota, 

Utah, and Wyoming) and in the State of 

Chihuahua, Mexico. No additional wild 

populations have been discovered to date. 

A thorough review of the background 

and history of the black-footed ferret 

recovery program can be found in Lockhart 

et al. (2006).
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Black-footed ferrets are specialist predators 

of prairie dogs and historically occurred 

throughout Colorado in association with 

colonies of black-tailed (C. ludovicianus), 

white-tailed (C. leucurus), and Gunnison’s 

(C. gunnisoni) prairie dogs (figure 1). 

However, populations declined and the 

ferret was eventually eliminated from its 

range in Colorado coincident with prairie 

dog eradication efforts, conversion of native 

prairie to other land uses, and disease outbreaks in the first half of the 20th century. 

The last confirmed ferret sighting in northwest Colorado occurred near Craig in Moffat 

County in 1943, and the last confirmed 

ferret sighting in the State occurred in 

Costilla County in 1946 (Anderson et al. 1986).

This report summarizes black-footed ferret 

reintroduction and recovery activities 

conducted within the Wolf Creek Management Area in northwest Colorado from 2001 

through 2006. Reintroduction of blackfooted ferrets in Colorado began in 2001 

with the release of captive-bred ferrets 

into the Wolf Creek Management Area and 

Coyote Basin Management Area (figure 2). 

The primary purpose of this reintroduction 

is to establish a self-sustaining population 

of ferrets in the wild in Colorado as part of 

a wider effort to restore populations of this 

species within its former range. Another 

goal of the program is to accomplish ferret 

recovery in northwest Colorado in a manner 

that is consistent with existing local 

lifestyles and economies. While a portion 

of the Coyote Basin site does occur in 

Colorado, it is managed as part of the ferret 

recovery program in Utah and will not be 

addressed in this report.

Cooperating Agencies 

and Parties

The recovery program for black-footed 

ferrets in northwest Colorado is a cooperative effort among the Colorado Division of 

Wildlife (CDOW), Utah Division of Wildlife 

Resources (UDWR), Bureau of Land 

Management (BLM), U.S. Fish and Wildlife 

Service (USFWS), and U.S. Geological 

Survey–Biological Resources Division 

(USGS–BRD). Because of the geographic 

location of reintroduction sites and proximity 

of ferret recovery efforts in Colorado and 

Utah, these two programs are closely 

linked, and many aspects of ferret recovery 

planning in the two States are coordinated 

by a single group, the Colorado/Utah BlackFooted Ferret Working Group. This group 

consists of representatives from those 

Figure 2. Location of the three black-footed ferret management areas in northwest Colorado.

Figure 1. Historic distribution records of black-footed ferrets and the range of three prairie dog species in Colorado 

(after Anderson et al. 1986).
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agencies listed above including three BLM 

field offices: the White River Field Office 

in Meeker, Colorado; the Little Snake Field 

Office in Craig, Colorado; and the Vernal 

Field Office in Vernal, Utah. In addition to 

these agencies, support for the program 

also comes from the Uintah Basin Campus 

of Utah State University (USU) and from 

the Animal and Plant Health Inspection 

Service (APHIS)–Wildlife Services. USU 

personnel provide technical advice and 

support for a variety of issues, including 

ferret management and monitoring, prairie 

dog monitoring, and disease research, 

while APHIS assists in collecting biological 

samples for implementation of the 

disease monitoring protocol associated 

with ferret reintroduction.

Program History and 

Authorization

Shortly after the remnant population 

of black-footed ferrets was found near 

Meeteetse, Wyoming, in 1981, CDOW and 

USFWS began searching for an existing 

population of ferrets in Colorado. At that 

time, they also began the process of identifying potential sites where ferrets could 

be reintroduced into Colorado in the future. 

While no ferrets were found during these 

efforts, three sites in northwest Colorado 

were identified as having potential for 

ferret reintroduction. These were the Little 

Snake Management Area in northwest 

Moffat County, the Wolf Creek Management 

Area in Moffat and Rio Blanco Counties, and 

the Coyote Basin Management Area in Rio 

Blanco County, which would be managed 

as part of a larger site in Coyote Basin, Utah. 

These areas were identified as suitable sites 

because each consisted of large complexes 

of white-tailed prairie dog colonies that 

occurred primarily on public lands.

Once the final animals were captured from 

the Meeteetse, Wyoming, population in 

1987 and captive breeding began, plans 

were immediately put in place to begin 

reintroducing ferrets into suitable habitat 

once the captive population was secure. 

The national Black-Footed Ferret Recovery 

Plan (U.S. Fish and Wildlife Service 1988) 

identified three recovery objectives:

1) Increase the captive population of 

black-footed ferrets to a census size 

of 200 breeding adults by 1991;

2) Establish a prebreeding census 

population of 1,500 free-ranging 

black-footed ferret breeding adults 

in 10 or more populations with no 

fewer than 30 breeding adults in any 

population by the year 2010; and

3) Encourage the widest possible 

distribution of reintroduced 

black-footed ferret populations.

Black-footed ferret reintroduction in northwest Colorado was authorized in 1998 with 

publication in the “Federal Register” of the 

final rule for “Endangered and Threatened 

Wildlife and Plants: Establishment of a 

Nonessential Experimental Population 

of Black-footed Ferrets in Northwestern 

Colorado and Northeastern Utah” (U.S. Fish 

and Wildlife Service 1998). Under section 

10(j) of the ESA, as amended, the USFWS 

may designate reintroduced populations 

as experimental and nonessential to the 

continued existence of the species. This 

designation gives Federal agencies more 

flexibility in managing the species by 

relaxing the responsibilities in section 7 

of the ESA. Section 7 directs all Federal 

agencies to use their authorities to conserve 

threatened and endangered species and 

ensure that their actions do not jeopardize 

listed species or destroy or adversely modify 

critical habitat. Populations designated as 

nonessential and experimental are treated 

as proposed for listing and are given fewer 

protections than a fully listed species. 

This designation also often increases local 

support for the reintroduction of listed 

species by giving assurances that current 

and future land uses will not be disrupted 

by the action. The experimental population 

area in northwest Colorado includes all of 

Moffat and Rio Blanco Counties west of 

State Highway 13.

The reintroduction of black-footed ferrets 

into Colorado also required State legislative 

approval. The Colorado State Legislature 

approved the reintroduction on April 

18, 2000, through House Bill 1314. This 

legislation and the subsequent Colorado 

Revised Statute 33-2-105.6 required that 

ferret reintroduction activities be conducted 

in a manner consistent with the approach 

used in the management plan for the Little 

Snake Management Area (U.S. Fish and 

Wildlife Service et al. 1995). Additionally, 

it called for recovery cooperators to provide 

regular updates to the local community on 

the status of reintroduction activities and 

required that representatives of local 

government and affected interests be 

involved in the resolution of issues that 

may arise during the reintroduction effort.

The original area planned for ferret releases 

in Colorado was the Little Snake Management Area. In 1989, this area contained at 

least 31,720 hectares (78,400 acres) of 

active white-tailed prairie dog colonies, 
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with approximately 95 percent of this 

occupied habitat occurring on BLMadministered public lands. However, 

this population of prairie dogs declined 

throughout the late 1990s, presumably 

due to an outbreak of sylvatic plague. As a 

result, the site was removed from consideration for ferret releases and another site 

was sought. The Wolf Creek Management 

Area (WCMA), located approximately 30 km 

(19 mi) south of the Little Snake Management Area, continued to support a sizeable 

white-tailed prairie dog population during 

this period and was identified as a suitable 

alternative release site.

In February 2000, the Wolf Creek Work 

Group was formed in order to develop a 

consensus-based management plan that 

would serve as a steering document for 

ferret recovery in the Wolf Creek and Coyote 

Basin (Colorado) Management Areas. This 

group consisted of representatives from BLM, 

CDOW, county government, recreational 

groups, energy companies, and the public 

at large. The product of the group’s work 

was “A Cooperative Plan for Black-Footed 

Ferret Reintroduction and Management—

Wolf Creek and Coyote Basin Management 

Areas, Moffat and Rio Blanco Counties, 

Colorado” (Wolf Creek Work Group 2001). 

This plan was patterned after a similar plan 

for the Little Snake Management Area in 

northwest Moffat County (U.S. Fish and 

Wildlife Service et al. 1995) and addressed 

all aspects of ferret management, including 

physical, biological, and social resources 

within the management areas; management roles associated with ferret recovery; 

program goals and objectives; land use 

issues and management strategies; and 

anticipated activities associated with 

implementation of the plan. A primary 

goal identified in the plan was that ferret 

recovery would be conducted in a way that 

was compatible with existing and future 

economies and lifestyles, including livestock management, mineral development, 

and recreation activities. The plan also 

called for ferret recovery in Wolf Creek to be 

a cooperative effort among Federal, State, 

and local governments and private entities.
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METHODS

Description of 

the Wolf Creek 

Management Area

THE WOLF CREEK MANAGEMENT AREA 

(WCMA) is located in northwest Colorado in 

Moffat and Rio Blanco counties (figure 3). 

Land ownership within the management 

area is predominantly public, BLMadministered land (90 percent) under the 

jurisdiction of the BLM’s White River Field 

Office. The remainder of the area consists 

of State (6 percent) and private (4 percent) 

holdings. The WCMA encompasses a large 

basin of approximately 21,000 hectares 

(52,000 acres) at the lower reaches of 

the Wolf Creek watershed; Wolf Creek is a 

tributary of the White River. The WCMA is 

Figure 3. Land ownership within the Wolf Creek Management Area.
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bounded on the south by Coal Ridge, on the 

east by Pinyon Ridge, and on the north by 

Elk Springs Ridge and its associated uplands 

stretching westward. The western end of 

the basin is contiguous with habitat occupied by prairie dogs that stretches without 

major geographic barriers all the way to 

the Colorado/Utah State line; however, the 

western boundary of the management 

area was defined as Moffat County Road 

95C because the proportion of privately 

held land increases substantially west of 

that point. Elevations range from 1,665 to 

1,890 meters (5,460 to 6,200 feet), and the 

topography is characterized by rolling hills 

and sloping valleys dissected by deeply 

cut drainages. Along the borders of the 

basin, there are typically steep escarpments 

that define the transition to surrounding 

uplands. The climate is continental and 

arid, characterized by cold winters and 

hot summers. Average yearly precipitation 

at the two nearest recording stations at 

Rangely, Colorado, about 25 km (16 mi) 

southwest of the WCMA, and Dinosaur, 

Colorado, about 30 km (19 mi) west of 

the WCMA), is 25.45 cm (10.02 in) and 

29.57 cm (11.64 in), respectively (Western 

Regional Climate Center 2007).

The major plant community present 

within the WCMA is the salt-desert shrub 

association, which is dominated by several 

shrub species and characterized by a sparse 

herbaceous understory. Common shrubs 

in these habitats include big sagebrush 

(Artemisia tridentata), black greasewood 

(Sarcobatus vermiculatus), winterfat 

(Krascheninnikovia lanata), and several 

species of saltbushes (Atriplex spp.). Understory species include western wheatgrass 

(Pascopyrum smithii), Salina wildrye 

(Leymus salina), Sandberg bluegrass 

(Poa secunda), cheatgrass (Bromus tectorum), 

and a variety of annual and perennial 

forbs. Along the eastern margin of the 

management area, there are more 

pure stands of big sagebrush as well as 

several large drainage bottoms dominated 

by grasslands. In addition to the grass- and 

shrub-dominated communities present, 

there are also several stands of pinyonjuniper (Pinus edulis-Juniperus osteosperma)

woodland present on ridgetops and where 

elevations are higher within the WCMA. 

Pinyon-juniper woodland is also the dominant habitat type surrounding the basin. 

Riparian habitat types are extremely limited 

within the WCMA, as even the main stem of 

Wolf Creek is intermittent. The little riparian 

habitat that exists is typically associated 

with artificial water impoundments.

The primary land uses within the WCMA are 

livestock grazing and big game hunting. 

Livestock grazing consists of winter sheep 

use and winter/spring cattle use. In general, 

the northern and eastern portions of the 

WCMA consist of sheep allotments, while 

the southern and western portions consist 

of cattle allotments. Slight reductions in 

overall grazing duration and intensity were 

incorporated into grazing permits reissued 

for several allotments within the WCMA 

since 2001. These reductions were intended 

to improve range condition and might be 

expected to improve the forage base available to native herbivores, including prairie 

dogs. Big game hunting for pronghorn 

antelope (Antilocapra americana), mule 

deer (Odocoileus hemionus), and elk (Cervus 

elaphus) occurs throughout the WCMA. 

Hunting activity generally occurs from 

August to October for pronghorn and during 

November and December for deer and elk.

Prairie Dog 

Management and 

Monitoring

There were approximately 7,700 hectares 

(19,000 acres) of active white-tailed prairie 

dog colonies distributed throughout the 

WCMA in 2006 (figures 4 and 5), although 

that figure certainly fluctuates on an annual 

Figure 4. White-tailed prairie dog distribution within the Wolf Creek Management Area. Colonies are labeled with 

numbers referred to in the text and in Appendix A.
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basis. Total occupied acreage was estimated 

at 6,800 ha (16,800 ac) in 2001 when blackfooted ferrets were first released. Colony 

sizes in 2006 ranged from 11 ha (27 ac) to 

1,460 ha (3,608 ac).

Land management activities within the 

WCMA that are administered by the 

BLM are conducted with the objective of 

maintaining at least 6,270 ha (15,500 ac) 

of occupied white-tailed prairie dog habitat 

(Wolf Creek Work Group 2001). Surfacedisturbing activities are permitted with 

conditions to avoid prairie dog colonies 

where possible, and offsite habitat 

enhancement for the purpose of increasing 

occupied prairie dog acreage is the preferred 

method of mitigation where adverse 

impacts to prairie dog colonies within the 

WCMA are unavoidable. Much of the WCMA 

was leased for oil and gas development in 

May 2006, but no exploration or development activities had occurred on these 

leases as of the end of 2006.

No special prairie dog shooting management guidelines were established in the 

WCMA as a result of black-footed ferret 

reintroduction because the perceived level 

of harvest in the area was assumed to be 

compatible with ferret habitat objectives. 

As such, management of prairie dogs in the 

WCMA remained consistent with statewide 

regulations. White-tailed prairie dogs in 

Colorado were historically managed as 

a small game species with a year-round 

season of harvest and unlimited bag and 

possession limits. However, in September 

2006, the Colorado Wildlife Commission 

passed a regulation that limited the season 

of harvest of all three species of prairie dogs 

in Colorado to June 15 through February 28 

to limit take during the period when prairie 

dogs are reproducing and have dependent 

young. This seasonal closure took effect in 

2007 and applies only to public lands (both 

Federal and State).

For the purpose of identifying complexes of 

prairie dog colonies suitable as black-footed 

ferret habitat, Biggins et al. (1993) proposed 

a method by which a group of colonies 

that are each within 7 km (4.4 mi) of one 

another are considered a complex and 

among which ferret movements may be 

expected. Demographically, such a complex 

would be expected to support a population 

of ferrets that exchanged individuals and 

genetic material among colonies. The 7-km 

distance was based on the longest observed 

Figure 5. An example of white-tailed prairie dog and black-footed ferret habitat within the Wolf Creek Management Area. This is a photograph of part of colony 20/23, where ferrets 

were found routinely during 2005 and 2006. Pinyon Ridge, the eastern boundary of the Wolf Creek Management Area, is in the background.
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nightly movement of a ferret in the 

remnant Meeteetse population. However, 

Biggins et al. (2006a) proposed modifying 

the 7-km distance to a distance of 1.5 km 

(.9 mi) based on observed movements of 

reintroduced ferrets at UL Bend National 

Wildlife Refuge in Montana, where 

85.5 percent of all intercolony movements 

were <1.5 km (Biggins et al. 2006b). This 

1.5-km distance is now accepted as a more 

typical intercolony or dispersal movement 

distance and is currently used to circumscribe 

complexes of prairie dog colonies for the 

purpose of ferret reintroduction.

In addition to defining a complex and 

determining total acreage occupied by 

prairie dogs, Biggins et al. (1993) also 

identified prairie dog abundance as a 

critical component of evaluating potential 

ferret habitat. They proposed a method by 

which belt transects 1,000 m (3,281 ft) 

long and 3 m (10 ft) wide are used to 

quantify prairie dog burrow density. Along 

these transects, the total number of 

active and inactive burrows are quantified. 

Active burrow density can then be used to 

estimate prairie dog population density and 

abundance and, based on ferret energetics, 

determine a minimum number of ferrets 

that a complex can support. This number is 

called the ferret family rating (FFR) where 

one “ferret family” consists of an adult 

female, her litter, and one-half of an adult 

male ferret. The minimum density of prairie 

dogs required to support a female ferret 

raising a litter based on this model was 

3.63 prairie dogs/ha, and areas supporting 

this minimum density of prairie dogs were 

considered “good habitat.”

Based on the modified 1.5-km complex 

circumspection rule, all colonies in the WCMA

were considered to represent one complex. 

The transecting method to determine 

prairie dog density and the minimum 

number of ferrets that 

an area should support 

was employed in the 

WCMA beginning in 

1989. However, different 

areas within the WCMA, 

sampling intensity, and 

sampling frequency 

were used throughout 

that time to quantify 

prairie dog population 

characteristics. Methods and transect routes 

were finally standardized in 2004. Table 1 

reports summary statistics for 5 years of 

transecting data. Data from 2002 and 2003 

are comparable to one another but not to 

data from 2004 to 2006 due to variations in 

methodology. Colony-specific transect 

summaries for 2004 to 2006 are included 

as Appendix A.

Wide fluctuations in prairie dog density, 

abundance, and FFR, such as those observed 

in the WCMA, are probably common in 

white-tailed prairie dog populations. These 

fluctuations are likely due to climatic factors 

and disease or some combination of these 

factors. The observed increase in prairie dog 

abundance in the WCMA from 2004 to 2006 

was most likely due to a return to average 

or above-average precipitation during 2005 

and 2006 following the drought years of 

2002 and 2003 (Western Regional Climate 

Center 2007). Both Maxfield (undated) and 

Van Pelt and Winstead (2003) indicated 

that prairie dog populations in their study 

areas appeared to fluctuate in response to 

climatic factors.

Disease Management 

and Monitoring

Two diseases, sylvatic plague and canine 

distemper virus (CDV), have played a 

prominent role in the management and 

conservation of black-footed ferrets 

throughout their range. Sylvatic plague 

is a flea-borne zoonotic disease (one that 

is maintained in wildlife populations but 

transferable to humans) caused by the 

bacterium Yersinia pestis that was introduced 

into North America from Asia around 1900. 

It is highly virulent to all species of prairie 

dogs and has been indicated as one of the 

primary threats to the persistence of prairie 

dog populations and recovery of the blackfooted ferret throughout North America 

(Barnes 1993, Cully and Williams 2001). In 

addition to causing high mortality within 

their primary prey, Y. pestis is also highly 

virulent to ferrets (Williams et al. 1994). 

CDV is a viral pathogen commonly spread by 

aerosol that causes central nervous system 

disease in infected animals. This disease 

primarily affects carnivores, although other 

taxa can also be affected. Black-footed 

ferrets are highly susceptible to CDV, which 

they are probably most often exposed to 

through interactions or habitat overlap with 

wild and unvaccinated domestic canids 

(Williams et al. 1988). Both sylvatic plague 

and CDV were found present at the Meeteetse, 

Wyoming, site in 1985 during a decline 

in the ferret population there, and these 

diseases probably acted synergistically in 

causing that decline, which eventually led 

to the elimination of black-footed ferrets 

in the wild.

Table 1. White-tailed prairie dog population attributes within the Wolf Creek 

Management Area, 2002 to 2006.

Year Prairie 

Dog/Ha

—

Entire 

Complex

Population 

Estimate 

—

Entire 

Complex

% Good 

Habitat

Prairie 

Dog/Ha -

Good 

Habitat

Population 

Estimate

—

Good 

Habitat

FFR

2002 3.2 18,843 38 6.6 14,846 18.4

2003 3.4 19,968 41 6.8 16,564 21.9

2004 2.7 21,112 29 7.0 15,485 19.6

2005 4.3 33,309 50 6.9 27,615 36.1

2006 7.2 52,650 74 9.1 49,519 64.1
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

9

To monitor the status of select diseases 

that may compromise the suitability of 

the WCMA as ferret habitat, coyotes (Canis 

latrans) were tested for serological evidence 

of exposure to Y. pestis and CDV within the 

WCMA each year from 2000 to 2005. In 

addition, coyotes were also tested for serological evidence of exposure to tularemia, a 

disease caused by the bacterium Francisella 

tularensis, which is not known to adversely 

affect ferrets but can cause mortality 

in rodents and lagomorphs. Serological 

surveys for disease determine exposure 

by looking for the presence of pathogenspecific antibodies in the blood of a host. A 

positive result indicates only that the host 

was exposed to the pathogen sometime 

during its life. The collection of coyotes was 

accomplished in cooperation with CDOW 

and APHIS–Wildlife Services. Coyotes were 

collected through a combination of calling 

and aerial gunning. Targeted sample sizes 

each year were 20, while actual sample size 

ranged from 11 to 21.

Evidence of exposure to Y. pestis among 

coyotes in the WCMA was absent each year 

from 2000 to 2003, but increased slightly 

each year in 2004 and 2005 (table 2). However, this increase in plague seroprevalence, 

or the rate at which blood serum from 

coyotes tested positive for plague, during 

those years did not appear to indicate an 

active plague outbreak because prairie dog 

populations also increased during that time 

period. Seroprevalence of exposure to CDV 

varied by year, but was generally low. The 

highest number of CDV seropositive coyotes 

(those with CDV antibodies present in the 

blood) were collected in 2000 (19 percent 

of those sampled were positive) and 2001 

(28 percent were positive), but these results 

indicate that this pathogen is probably 

consistently present within the WCMA. In 

contrast to plague and CDV, tularemia 

seroprevalence was high each 

year of sampling, with the 

proportion of positive coyotes 

ranging from 26 percent to 

44 percent. As with plague, 

though, the presence of tularemia did not appear to have a 

great negative effect on prairie 

dog populations, as they have 

increased in the presence of 

seemingly high tularemia 

infection rates.

Because of cost and some limitations inherent in interpreting the 

results of disease surveillance 

conducted through opportunistic 

carnivore sampling, this method 

was discontinued in 2006. As 

an alternative, disease surveillance was accomplished through 

sampling small mammals within 

the WCMA. This method offers 

greater spatial and temporal 

resolution in monitoring disease 

activity due to the small home 

ranges and short lifespans typical of most 

small mammals. A much larger sample size 

was gathered using this method, and it was 

also more economical than contracting 

through APHIS–Wildlife Services. Staff 

from the CDOW Wildlife Health Program 

managed the sampling, which consisted 

of taking blood samples from live-trapped 

small mammals at a number of locations 

within the WCMA. Samples were tested 

for evidence of exposure to plague and 

tularemia but not CDV because rodents 

are not known to be hosts for CDV. Field 

sampling was carried out in early August 

2006 and samples were gathered from 

303 small mammals representing the 

following genera: Peromyscus (n=290), 

Tamias (n=10), Onychomys (n=2), and 

Reithrodontomys (n=1). All samples were 

negative for plague and tularemia.

Two prairie dog colonies totaling 347 ha 

(857 ac) were treated with an insecticide 

dust to kill fleas and reduce Y. pestis 

transmission during the summers of 2004 

and 2005. This test was part of a collaborative research project to determine the 

efficacy of this treatment for increasing 

ferret and prairie dog survival. The goal 

was to identify whether low levels of Y. 

pestis infection may have been negatively 

impacting ferret or prairie dog survival. On 

the treated colonies (colonies 6 and 13) 

every burrow was treated with 4 g of 

0.05 percent deltamethrin formulation 

(Delta Dust®, manufactured by Bayer 

Table 2. Disease surveillance results from coyote serological surveys 

for the Wolf Creek Management Area, 2000 to 2005.

Sampling 

Period

Plague

# Tested Positive Negative % Positive

2000 19 0 19 0.00

2001 17 0 17 0.00

2002 13 0 13 0.00

2003 11 0 11 0.00

2004 20 1 19 5.00

2005 19 4 15 21.05

Canine Distemper Virus (CDV)

# Tested Positive Negative % Positive

2000 21 4 17 19.05

2001 18 5 13 27.78

2002 12 0 12 0.00

2003 11 1 10 9.09

2004 20 1 19 5.00

2005 19 2 17 10.53

Tularemia

# Tested Positive Negative % Positive

2000 21 9 12 42.86

2001 16 7 9 43.75

2002 13 5 8 38.46

2003 11 3 8 27.27

2004 20 8 12 40.00

2005 19 5 14 26.32
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

10

Environmental Science, Montvale, New 

Jersey), a synthetic pyrethroid insecticide 

labeled for the control of fleas in rodent 

burrows. Subsequent ferret releases on 

these treatment colonies included both 

plague-vaccinated and control animals (see 

the “Releases” section). Treatment effects 

on ferret survival could not be determined 

because none of the ferrets released on 

these colonies during 2004 and 2005 were 

ever relocated. There was no apparent treatment effect on prairie dog populations at 

the two treatment colonies, based on yearly 

monitoring transects, but this method is 

probably not sensitive enough to detect 

small changes in survival. Furthermore, 

any treatment effect (or lack of treatment 

effect) could have been confounded by 

other factors including predation, 

recreational shooting pressure, or local 

habitat conditions, for which no controls 

were established.

Black-Footed Ferret 

Management

Allocation and 

Preconditioning

To obtain black-footed ferrets for release 

into the wild, agencies and organizations 

involved in ferret reintroduction submit 

allocation proposals to the USFWS. Sites 

requesting ferrets are ranked according to 

a number of factors, including suitability of 

habitat, disease status and management, 

past ferret survival, kit production, 

research contributions, and long-term site 

conservation. The final decision as to how 

many ferrets each site receives, as well as 

the sex and age makeup of those animals, 

is made by the USFWS’s black-footed ferret 

recovery coordinator. The majority of ferrets 

released each year are captive-reared 

animals that are produced at the National 

Black-Footed Ferret Conservation Center in 

Fort Collins, Colorado (formerly in Sybille, 

Wyoming). However, a number of other 

facilities also have captive-breeding programs for black-footed ferrets and 

contribute to the pool of ferrets available 

each year for release into the wild. In 

addition, some wild-born ferrets from the 

Conata Basin reintroduction site in South 

Dakota have been captured and transplanted 

to other sites.

Captive-bred ferrets reared in cages and 

released into the wild with no prerelease 

experience living in a natural environment 

or capturing live prey have lower survival 

rates than animals preconditioned in quasinatural environments (Biggins et al. 1998). 

Because of this, ferret preconditioning 

has been an integral part of the Colorado 

reintroduction program. The BLM’s Little 

Snake Field Office manages “onsite” preconditioning pens near Browns Park in Moffat 

County. The site was built on a white-tailed 

prairie dog colony and 

consists of 20 pens, each 

about 21 by 21 meters 

(70 by 70 feet). White-tailed 

prairie dogs are trapped by 

CDOW each year from near 

Grand Junction, Colorado, 

and provided to the facility 

for preconditioning 

activities. Ferrets allocated 

to both Colorado and Utah 

were maintained in these 

pens for 30 to 60 days, 

during which time they 

were exposed to the natural 

environment of prairie dog 

burrows and to live prairie 

dogs so that they could 

develop hunting skills.

Releases

A total of 217 ferrets were released in 

the WCMA from 2001 to 2006 (table 3, 

figure 6). Of those, 184 (85 percent) were 

kits when they were released and 33 

(15 percent) were adults. The release of 

captive-born ferrets occurs in the late 

summer or fall to correspond with the time 

period when kits would naturally disperse 

from their maternal territory, so kits are 

the preferred age-class for release. Most 

ferrets (207/217, or 95 percent) released in 

the WCMA during this period were 

captive-raised animals that came from one 

of several facilities across the United States. 

However, 10 ferrets released in 2003 were 

wild-born animals that were transplanted 

from Conata Basin, South Dakota. The 

number of ferrets released in any given year 

ranged from 19 to 63. Appendix B details 

the origin and release data for all ferrets 

released within the WCMA. Appendix B also 

includes maps of release locations within 

the WCMA for all years but 2001, for which 

this data was not available.

Table 3. Summary of black-footed ferrets released within the 

Wolf Creek Management Area, 2001 to 2006.

# CaptiveBorn

Released

# WildBorn

Released

Total

Inclusive

Release 

Dates

Year 

Total

Year Sex Kits Adults All Kits

2001 Male

Female

17

11

0

7

0

0

17

18

11/15/01 

to

11/23/01

35

2002 Male

Female

8

12

1

7

0

0

9

19

8/15/02 to

11/19/02

28

2003 Male

Female

17

20

2

14

6

4

25

38

8/16/03 to

11/19/03

63

2004 Male

Female

25

18

0

1

0

0

25

19

10/6/04 to

11/16/04

44

2005 Male

Female

13

6

0

0

0

0

13

6

10/13/05 

to

11/2/05

19

2006 Male

Female

17

10

0

1

0

0

17

11

9/26/06 to

11/9/06

28

Grand Total 217
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

11

All ferret releases in Colorado have been 

“hard” releases. That is, ferrets did not have 

onsite cages or nest boxes that they could 

return to following release. Instead, ferrets 

were released into areas of high prairie dog 

density (as determined by transecting) 

without further support. Areas with high 

prairie dog density were chosen for release 

because prey density is considered the 

most important habitat characteristic 

for ferrets (Biggins et al. 2006b). Prior to 

release, all ferrets were implanted with two 

passive integrated transponder (PIT) chips 

(American Veterinary Identification Devices, 

Norco, California). These chips, which are 

approximately the size of a large grain of 

rice, were implanted subcutaneously in 

the neck and near the pelvis. Each chip 

contains a unique nine-digit number that is 

activated by a specialized reader and allows 

for the individual identification of ferrets 

for the life of the animal. Two chips were 

implanted to create a redundancy whereby 

if one chip fails, identification can still be 

made with the remaining chip.

All ferrets released in the WCMA received a 

series of two canine distemper vaccinations 

(Purevax® Ferret Distemper, manufactured 

by Merial, Inc, Athens, Georgia). Beginning 

in 2004, a subset of ferrets also received 

a plague vaccine as part of a research 

program to determine whether vaccinating 

ferrets against plague would protect 

them against low levels of plague activity 

and increase survival. Increased survival 

of plague-vaccinated ferrets has been 

observed on black-tailed prairie dog 

habitat in Montana (D. Biggins, personal 

communication) and researchers desired 

to expand this research to include ferret 

reintroduction sites within white-tailed 

prairie dog habitat.

Figure 6. All black-footed ferret release locations within the Wolf Creek Management Area, 2002 to 2006 (2001 data not available).
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

13

Monitoring Efforts

Spotlighting

THE MOST COMMONLY USED METHOD of 

monitoring black-footed ferrets is nocturnal 

spotlighting (Clark et al. 1984, Campbell 

et al. 1985). This method involves using 

high-intensity spotlights, either mounted 

on a vehicle or carried on foot, at night. 

The goal of this survey technique is to locate 

ferrets when they are most active at night 

by illuminating their characteristic bright, 

emerald green eyeshine. While the eyeshine 

of other animals such as coyotes, badgers 

(Taxidea taxus), and pronghorn also reflects 

green, positive identification of ferrets can 

be made by close approach of the animal 

in question. When spotlighting, searchers 

typically use continuous illumination while 

slowly moving through a prairie dog colony, 

constantly scanning from dusk until dawn 

for a minimum of 3 consecutive nights.

The most intense spotlight surveys for 

ferrets in the WCMA took place each year, 

beginning in 2002, in either August or 

September, when kits are often active 

aboveground in litter groups and litter 

size and maternity can be quantified. 

These intense survey efforts were timed 

to coincide with the full moon and were 

held over 10-day periods so that multiple 

colonies could be adequately surveyed. 

Due to the large area of white-tailed 

prairie dogs in the WCMA, about 7,700 ha 

(19,000 ac), only a portion of the area could 

be surveyed. Those colonies or portions of 

colonies that were surveyed each year were 

chosen based on past ferret occupancy and 

high prairie dog density as determined by 

yearly monitoring transects. In addition to 

the intense late summer spotlight surveys, 

additional surveys were conducted in the 

WCMA in the late fall and early winter 

(October to December) to determine the 

short-term survival of recently released 

ferrets and in the spring (March to April) to 

determine overwinter survival and identify 

the potential breeding population. Once a 

ferret was located, an attempt was made to 

either identify the animal with a hand-held 

RESULTS
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

14

PIT reader by placing its circular antenna 

over the occupied burrow (figures 7a and b) 

or by trapping, depending on survey 

objectives. Any wild-born ferrets encountered 

were captured, implanted with two PIT 

chips, and given a CDV vaccination, as 

described previously for captive-born 

ferrets that were released into the wild.

Spotlight surveys were initiated in the 

WCMA in 2002, and the total survey effort 

ranged from about 700 hours to over 

1,200 hours per year (figure 8). The majority 

of this effort was conducted on foot 

because vehicle travel in the WCMA is 

restricted to existing roads, and a relatively 

small proportion of the overall prairie dog 

colony acreage is visible from roads. The 

total number of individual ferrets observed 

within the WCMA each year is reported in 

table 4. Only confirmed observations are 

reported in table 4. Confirmed observations were those observations in the field 

that were made at close range to be sure 

that the animal was a black-footed ferret 

or those observations that resulted in a 

PIT chip reading or capture. Unconfirmed 

observations of green eyeshine are not 

included in these totals. Postrelease 

observations include animals that were 

released in a given year and that survived 

at least 30 days following release. These 

observations were made during the late 

fall and early winter survey period and are 

a standard measure of short-term survival 

in ferret recovery programs (e.g., Biggins et 

al. 2006c).

Radio Telemetry

The initial black-footed ferret release in the 

WCMA occurred on November 15, 2001, and 

consisted of 23 kits and 7 adults. To track 

postrelease movements and survival, the 

23 kits were fitted with radio transmitters 

with a frequency range of 164-165 MHz 

and an average expected battery life of 

45 days. Monitoring consisted of both aerial 

telemetry (five night flights and two day 

flights) and ground telemetry carried out 

from November 14, 2001, to January 7, 

2002. Inclement weather resulted in fewer 

telemetry flights than were originally 

planned. Transmitters and collars from 

10 of the ferrets were recovered: two 

were confirmed to be dropped collars, 

four were from ferret mortalities, and 

four were inconclusive as to whether they 

Figure 7. a) An example of the 6-inch-diameter circular antenna of a hand-held passive integrated transponder (PIT) 

reader over the entrance of a prairie dog burrow.

Figure 7. b) In this picture, the PIT reader is in a storage pouch and connected to a 12 V power source.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

15

Table 4. Total number of individual black-footed ferrets observed within the 

Wolf Creek Management Area, 2001 to 2006.

2001 2002 2003 2004 2005 2006

Ferrets Alive 30 Days Postrelease 6 1 2 3 6 3

Ferrets From Previous Years N/A 1 1 3 6 8

Wild-Born Ferrets N/A 0 0 0 1 2

Minimum Yearend Population 

Estimate

6 2 3 6 13 13

Figure 8. Total spotlighting survey effort by year in the Wolf Creek Management Area, 2002 to 2006. Bars represent 

total effort expended throughout the year, but the bulk of survey time occurred in August and September.

were dropped collars or mortalities. The 

four mortalities were determined to be 

caused by a coyote in two cases, a golden 

eagle (Aquila chrysaetos), and an unknown 

raptor. Of the remaining 13 ferrets from 

which transmitters were not recovered, 

several were relocated during telemetry 

monitoring up to 3 weeks following their 

release, but many were not relocated again 

following release. A conservative estimate 

of short-term (30-day) mortality was 

26 percent (6/23) for these first kits 

released in the WCMA.

In the fall of 2005, 11 captive-raised ferrets 

were again fitted with radio transmitters 

prior to release in an effort to document 

postrelease movements and survival. Spotlight surveys between 2002 and 2004 had 

resulted in very few ferret observations and 

the telemetry work 

carried out during the 

fall and early winter 

of 2005 was intended 

to help address some 

questions regarding the 

short-term survival and 

movements of captiveraised ferrets released 

into the wild within the WCMA. The radio 

transmitters (Wildlife Materials, Inc., 

Murphysboro, Illinois) weighed approximately 

5 g (.18 oz), had a 20-cm (7.9-inch) whip 

antenna, and were affixed to animals as 

described in Biggins et al. (2006c). The 

frequency range used was 150-151 MHz, 

and the transmitters had an average 

expected battery life of 50 days. Radiocollared animals were released between 

October 13 and October 26, 2005, and 

followed using hand-held receivers (model: 

R-1000; Communication Specialists, Inc., 

Orange, California) and three-element 

folding Yagi antennas.

Of the 11 animals released with radio 

collars, three were killed by predators 

within 1 week of release. The heads of two 

ferrets, with collars still attached, were 

found shallowly buried outside of the 

colony where the ferrets were released, 

which was consistent with coyote predation 

observed during ferret telemetry work 

at other reintroduction sites (D. Biggins, 

personal communication). The third 

mortality was confirmed upon retrieval of 

the ferret’s collar, which showed evidence 

of predation, including a rip and bite marks 

on the transmitter package; however, the 

type of predator could not be confirmed. Of 

the remaining eight radio-collared ferrets, 

six shed their collars within several days 

of their release, one was not located again 

beginning the day after its release, and one 

was followed for the life of the collar. Shed 

collars were confirmed by excavating the 

burrow within which the collar was stationary for more than 3 consecutive days. The 

single ferret that was followed for the life 

of its collar was a juvenile male released on 

October 19, 2005. This individual remained 

at the colony where he was released (colony 

25) while moving about 750 m (2,461 ft) to 

the east during the telemetry monitoring 

period; he still occupied this same general 

area at the end of 2006 as determined by 

spotlight surveys.

Because a large proportion of radiocollared ferrets shed their collars shortly 

after release, data gained on postrelease 

movements and survival of captive-raised 

animals released in the WCMA were 

minimal. However, this telemetry work did 

confirm some trends seen at other release 

sites, namely that captive-raised ferrets can 

be particularly susceptible to predation 

shortly after release and that ferrets 

released into good habitat with sufficient 

prey may demonstrate limited postrelease 

movements, thereby increasing survival by 

limiting exposure to predators and reducing 

energetic expenditure.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

16

Working Dogs for 

Conservation

Working Dogs for Conservation is an organization based in Three Forks, Montana, 

that specializes in using scent dogs to 

detect wildlife species and their signs. 

In May 2005, they were contracted to 

conduct searches for black-footed ferrets 

in the WCMA because spotlight searches 

conducted during the previous 3 years had 

resulted in few confirmed ferret detections. 

Two dogs trained to indicate on the scent of 

live ferrets, both with previous experience 

in ferret searches, searched for a total of 

approximately 37 hours on seven different 

colonies. Between the two dogs, a total of 

36 burrows were indicated, suggesting 

ferret occupancy. Of those burrows indicated 

by one dog, four were “confirmed” by blind 

“double-checking” by the second dog, 

which indicated on the same burrow. In 

four other cases, the second dog indicated 

on a burrow within 50 m (164 ft) of a 

burrow indicated by the first dog. However, 

followup spotlight searches and PIT reader 

deployment on the eight “double-checked” 

burrows resulted in no confirmed ferret 

observations. Whitelaw et al. (2005) discuss 

interpretation of these results and offer 

further suggestions for the use of scent 

dogs in searches for black-footed ferrets.

Snowtracking

The use of snowtracking as a survey method 

for locating and studying black-footed 

ferrets was described by Clark et al. (1984). 

This technique was used opportunistically 

in the WCMA during the first 5 years of the 

reintroduction program when proper snow 

conditions existed. The locations of four 

individual ferrets were confirmed through 

snowtracking between December 2001 and 

February 2002, but no ferret locations have 

been confirmed through snowtracking since 

then. The snowtracking effort expended in 

the winter of 2001-2002 was 500 hours, 

but only about 80 hours of effort were 

expended each of the following two winters 

on snowtracking. Since then, only limited, 

opportunistic snowtracking efforts have 

been expended, mostly due to poor snow 

cover within the WCMA. However, given 

adequate snow conditions, snowtracking 

can be a useful tool in locating ferrets and 

studying winter movement patterns and 

habitat use (Richardson et al. 1987).

Reproduction in 

the Wild

The goal of the Wolf Creek black-footed 

ferret recovery program is to establish a 

self-sustaining population that does not 

require constant population augmentation. 

As such, reproduction by free-ranging ferrets is central to the success of the program. 

Three wild-born ferrets were documented 

within the WCMA by the end of 2006. The 

first wild-born kit was captured and marked 

on November 20, 2005, and two additional 

kits were captured and marked in September 

and November of 2006. While maternity 

was not confirmed for the kit (WC05-01) 

located in 2005, maternity was confirmed for 

the two kits (WC06-01, WC06-02) located 

in 2006. Ferret WC06-01 was the kit of 

WC05-01, the 1-year-old wild-born female 

from 2005, making her a second generation 

wild-born. Ferret WC06-02 was the kit of 

ferret 4884, a 1-year-old female released 

in 2005. All three wild-born kits came from 

colony 20/23 (a single large colony that 

is separated for the sake of prairie dog 

monitoring), and all three represented 

litters of one kit each.

Previously reported average litter sizes at 

emergence for ferrets in the wild include 

3.5 (n=11) for ferrets inhabiting blacktailed prairie dog colonies in South Dakota 

(Linder et al. 1972, as reported in Hillman 

and Clark 1980), 2.2 (n=38) for reintroduced ferrets inhabiting black-tailed prairie 

dog colonies in Montana (Matchett 1999), 

and 3.3 (n=68) for ferrets inhabiting 

white-tailed prairie dog colonies at 

Meeteetse, Wyoming (Forrest et al. 1988). 

The average litter size of 1.0 observed in the 

WCMA was substantially lower than those 

reported values and is probably insufficient 

to compensate for annual mortality experienced at the site. Such small litter sizes 

may be a function of the energetic costs of 

females living in an environment with low 

prey densities. Overall prairie dog densities 

throughout the WCMA are the lowest 

reported from any current reintroduction 

site. Even though much of the area supported 

densities of at least 3.63 prairie dogs/ha, 

which Biggins et al. (1993) predicted to be 

the minimum density necessary to support 

reproducing females, reproduction was 

only documented in colonies with average 

prairie dog densities of greater than 

5.5 prairie dogs/ha as determined by yearly 

transecting. In addition, females with 

litters appeared to use patches of high 

burrow densities within these colonies. This 

observation is consistent with recent work 

in South Dakota and Montana by Jachowski 

(2007), who found that female ferrets 

select and compete for patches of high 

prairie dog density on black-tailed prairie 

dog colonies in his study area, where prairie 

dog densities were much higher than those 

in the WCMA.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

17

Population Size, 

Survival, and 

Movements

To date, black-footed ferret reintroduction 

programs have relied on spotlighting as the 

primary means of surveying for ferrets and 

determining population status. This tecnique, 

as presently used, only provides a minimum 

number of animals known to be alive. 

Therefore, a complete or near-complete 

survey of all habitat has been required to 

estimate minimum population size, and it is 

this figure that has been commonly used to 

report ferret population status.

The total number of ferrets observed each 

year is shown in table 4. The number of 

ferrets observed during 30-day postrelease 

surveys is an indicator of short-term 

survival of captive-born animals, but survey 

efforts during this time period (October– 

December) were not consistent from year 

to year. A better indicator of trends in the 

overall ferret population is the number of 

animals relocated from previous years and 

the number of wild-born ferrets detected 

during yearly summer surveys conducted in 

August or early September because efforts 

were similar each year. A steady increase in 

numbers was observed from 2002 to 2006, 

with a minimum yearend population of 

13 ferrets in 2006.

A spring survey was conducted in the 

WCMA in mid-March of 2006. The purpose 

of this survey was to assess overwinter 

survival and document the minimum spring 

population size. A minimum prebreeding 

(spring) population of 30 ferrets was 

identified in the national recovery plan (U.S. 

Fish and Wildlife Service 1988) as a goal 

for individual reintroduction sites. Hours 

expended during this survey were much 

fewer than during the annual summer survey because of limited personnel; however, 

five ferrets were located with survey efforts 

concentrated on what was considered to 

be the best habitat. Subsequent surveys 

throughout 2006 found additional animals 

present that were not located during the 

spring survey, indicating that at least nine 

ferrets were present in the spring of 2006.

Figure 9 shows the locations of all blackfooted ferrets observed from December 

2001 until the end of 2006. The amount 

of search effort required per unique ferret 

Figure 9. All black-footed ferret relocations within the Wolf Creek Management Area, 2001 to 2006. Locations in green represent 1) captive-born ferrets that survived 

to at least the following spring to enter their first breeding season and 2) wild-born ferrets. Locations in blue represent ferrets relocated in the year they were 

released that survived at least 30 days in the wild following release.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

18

observation was 140 hours during the 

summer of 2005 (5 ferrets, 700 hours), 

70 hours during the summer of 2006 

(9 ferrets, 630 hours), and 18 hours during 

the spring of 2006 (5 ferrets, 90 hours), 

when only areas with the highest probability 

of containing ferrets were surveyed. These 

search effort figures are comparable to 

the amount of spotlighting time required 

per unique ferret observation at another 

reintroduction site on white-tailed prairie 

dog habitat in Shirley Basin, Wyoming, 

reported by Biggins et al. (2006d). There, 

search efforts ranged from 12 to 126 hours 

per unique observation with a median of 

52 hours (n=8 survey periods).

Most of the ferrets observed to date have 

been located in the eastern portion of 

the WCMA, and survival appears to differ 

among release colonies (see figure 6 vs. 

figure 9). The colonies in the eastern portion 

of the WCMA where most ferrets were 

located (colonies 18, 20/23, and 25) total 

about 1,100 ha (2,718 ac) in size and 

represent about 14 percent of the currently 

mapped prairie dog habitat in the WCMA. 

However, ferrets released in these colonies 

have been reencountered more often than 

ferrets released on other colonies in the 

WCMA. Too few ferrets were relocated from 

release cohorts prior to 2004 to make 

reliable estimates of survival; however, 

minimum apparent survival to 1 year for 

ferrets released in these eastern colonies 

was 33 percent (2/6) for ferrets released 

in 2004 and 43 percent (6/14) for ferrets 

released in 2005. In addition, all three 

wild-born ferrets documented to date have 

come from these colonies. In contrast, 

minimum apparent survival to 1 year for 

ferrets released throughout the remainder 

of the WCMA colonies was 3 percent (1/38) 

for ferrets released in 2004 and 0 percent 

(0/5) for ferrets released in 2005. The one 

ferret from the 2004 release that was 

documented to have survived to 1 year, a 

female (4745), was relocated on colony 

20/23 in the eastern portion of the WCMA 

the following summer, having dispersed 

more than 7 km (4.35 mi) from her release 

location (figure 10). This was the second 

ferret documented to disperse a long 

distance into colony 20/23; a male released 

in 2003 (P393) moved more than 10 km 

(6.21 mi) from his release location into this 

colony (crossing U.S. Highway 40 along the 

Figure 10. Documented long-distance, intercolony dispersal movements by ferrets within the Wolf Creek Management Area.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

19

way), where he apparently established a 

territory and was relocated several more 

times. Ferret P393 was still alive at the end 

of 2006, making him 3.5 years old and one 

of the two oldest ferrets located to date in 

the WCMA. A female ferret (P316) was also 

documented to have survived to 3.5 years old 

when she was last located in December 2005.

Overall, long-term survival (survival to 

1 year) for captive-raised ferrets released 

in the WCMA was low compared to 

other release sites, but survival of ferrets 

released on the three eastern colonies was 

equivalent to or higher than that recorded 

at other release sites (Biggins et al. 2006c). 

The observed differences in survival among 

colonies within the WCMA may have 

been due to differences in habitat quality, 

predation, disease dynamics, or other 

factors. In regard to habitat quality, prairie 

dog densities at colonies 18, 20/23, and 

25 were consistently among the highest in 

the WCMA. In addition, the proportion of 

these colonies with a minimum density of 

3.63 prairie dogs/ha, considered by Biggins 

et al. (1993) to represent “good” habitat, 

was also consistently high (Appendix A). In 

general, areas with high prairie dog density 

represent better habitat than areas with 

low prairie dog density because searching 

out and securing prey is less energetically 

costly. However, burrow density itself may 

also influence how ferrets use prairie dog 

colonies. Forrest et al. (1985) and Biggins 

et al. (2006b) discuss how areas with high 

burrow density would be beneficial to ferrets 

by providing escape cover and reducing the 

time spent aboveground traveling between 

burrows when ferrets are most susceptible 

to predators. Unfortunately, there is no data 

available on the abundance or distribution 

of potential ferret predators in the WCMA 

that might help explain observed differences 

in ferret survival.

Another factor possibly driving differences 

in ferret survival was disease, primarily 

plague. Beginning in 2004, approximately 

half of the ferrets released received a 

plague vaccine as part of an experimental 

trial to determine if this vaccine is effective 

in increasing ferret survival in areas where 

plague may exist at low levels. None of the 

three ferrets that were released in 2004 

and relocated in summer 2005 had been 

vaccinated against plague, while four of the 

six ferrets released in 2005 and relocated 

in summer 2006 were vaccinated against 

plague. Results from this vaccine trial in 

the WCMA and in Coyote Basin, Utah, are 

equivocal so far, with no clear pattern of 

differences in survival between vaccinated 

and control groups.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

21

DISCUSSION AND 

RECOMMENDATIONS

THE OBSERVED PATTERNS of ferret habitat 

use, survival, and reproduction in the wild 

imply that not all prairie dog colonies 

within the WCMA were equally suitable for 

ferrets, and in particular, for female ferrets 

attempting to raise a litter. Ferret survival 

and longevity within a subset of colonies 

in the eastern portion of the WCMA were 

equivalent to and, in some cases, higher 

than what has been observed at other 

reintroduction sites, including sites currently 

supporting large, apparently self-sustaining 

populations. However, survival in much of 

the rest of the WCMA was very low and all 

three litters documented were of a single 

surviving kit, which is also low compared 

to other reintroduction sites and probably 

insufficient to maintain a stable 

population in the absence of yearly 

supplemental releases.

The variable pattern of success observed at 

different colonies in the WCMA was probably not an artifact of survey procedures. 

While spotlighting is difficult within the 

WCMA because of rugged terrain, relatively 

heavy shrub cover, and lack of vehicle 

access, hundreds of hours of spotlighting 

were conducted each year, both within 

those colonies where survival and reproduction have been documented and in other 

colonies where few if any ferrets have 

been relocated. In addition, the adequacy 

of surveys in areas where ferrets have not 

been found has been supported through 

the observation of other infrequently 

observed small carnivores such as badgers, 

long-tailed weasels (Mustela frenata), and 

bobcats (Lynx rufus) in those areas. In one 

instance, a long-tailed weasel (presumed to 

be a single individual) was observed in the 

same location on successive nights by two 

separate crews, both without prior knowledge of its presence. On the other hand, 

ferrets were likely missed during surveys, 

as indicated by their detection during a subsequent survey. At least three consecutive 

nights of surveys were attempted in each 

area, but this was not always accomplished 

due to weather or other logistical constraints. Large areas of prairie dog habitat 

within the WCMA also required a tradeoff 

between survey effort intensity in a given 

area and adequate coverage of all suitable 

habitat. The recommendation of Biggins et 

al. (2006d) that an area should be covered 

at least every 30 to 60 minutes during that 

3-day period was not met in WCMA surveys. 

Experience gained in the WCMA, as well 

as that reported by Biggins et al. (2006d) 

for another white-tailed prairie dog 
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

22

reintroduction site (Shirley Basin, 

Wyoming) and a Gunnison’s prairie dog 

reintroduction site (Aubrey Valley, Arizona), 

indicates that a larger amount of effort 

is required for each ferret observation at 

these types of sites than at many blacktailed prairie dog reintroduction sites. This 

is probably due to the fact that whitetailed and Gunnison’s prairie dog colonies 

are characterized by higher amounts of 

shrub cover and lower overall prairie dog 

densities, with concomitantly lower ferret 

densities. Given this information, managers 

should strive to meet or exceed the 

minimum survey requirements proposed 

by Biggins et al. (2006d) when dealing 

with ferret reintroductions at white-tailed 

and Gunnison’s prairie dog reintroduction 

sites in order to gain reliable data on ferret 

survival and population size.

In the absence of plague outbreaks, and 

with no evidence to suggest that low levels 

of plague were reducing ferret survival, the 

most likely factor influencing ferret 

demographic rates in the WCMA was 

habitat quality (the density of prairie dogs 

and their burrows). Among current ferret 

reintroduction sites, the WCMA exhibits the 

lowest overall prairie dog density. Given 

that the most energetically expensive 

aspect of ferret natural history is the rearing 

of young by females, litter size might be 

predicted to decline in the absence of 

sufficient prey density. Variation in litter 

size is strongly tied to prey density for many 

species of carnivores (Fuller and Sievert 

2001), and this relationship should theoretically be even more pronounced for a 

specialist predator such as the black-footed 

ferret where prey-switching is not a viable 

option. Biggins et al. (1993) predicted that 

a minimum prairie dog density of 3.63/ha 

is required to support a female ferret with 

young during the litter-rearing period, and 

many colonies within the WCMA met this 

minimum threshold. However, ferrets were 

not reencountered following release on 

most of these colonies and litters were only 

documented on colonies where prairie dog 

density was 5.5 prairie dogs/ha or higher.

Most of the recent research on black-footed 

ferrets has taken place at reintroduction 

sites within the range of black-tailed prairie 

dogs, a species that naturally occurs at 

higher densities than white-tailed prairie 

dogs (Hoogland 1981). Additional research 

on ferret resource selection and demography at white-tailed prairie dog sites is 

needed. Of the three ferret reintroductions 

attempted at white-tailed prairie dog 

sites, only one (Shirley Basin, Wyoming) 

currently supports a large population of 

ferrets that may be considered selfsustaining. However, the last known 

population of free-ranging ferrets from 

near Meeteetse, Wyoming, existed on a 

white-tailed prairie dog complex, evidence 

that white-tailed prairie dogs provide 

potentially high-quality habitat for ferrets. 

Much of the landscape within the range of 

the white-tailed prairie dog is still intact 

and in public ownership, providing good 

opportunities for the development of future 

release sites. Therefore, a better understanding of what conditions are needed to 

support a viable ferret population at whitetailed prairie dog sites will serve the greater 

conservation needs of ferrets.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

23

APPENDIX A: COLONY-SPECIFIC 

PRAIRIE DOG TRANSECT SAMPLING

Summary for the Wolf Creek

Management Area, 2004–2006
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table A-1. 2004 Wolf Creek Management Area transecting summary.

Colony Size Active 

Ratio

Ha 

Sampled

Active/Ha Total/Ha PD Density 

- Total

PD # Total BFF Rating 

-Total

Ha Good % Good Active/Ha 

- Good

Total/Ha 

- Good

PD Density 

- Good

PD # Good BFF Rating 

- Good

1 1281 0.65 12.600 16.51 41.98 2.43 3119 4.09 305.01 23.81 48.67 81.00 7.18 2189 2.87

2 86 0.90 1.125 16.89 35.56 2.49 214 0.00 22.94 26.67 63.33 80.00 9.34 214 0.00

3 52 0.56 0.945 9.52 26.46 1.40 73 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

4 36 0.09 0.600 3.33 40.00 0.49 18 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

5 25 0.00 0.300 0.00 23.33 0.00 0 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

6 170 2.50 1.935 33.59 47.03 4.95 842 1.10 73.80 43.41 61.90 76.79 9.13 674 0.88

7 44 0.00 0.525 0.00 17.14 0.00 0 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

8 473 0.87 8.295 35.08 75.35 5.17 2447 3.21 277.98 58.77 51.08 87.79 7.53 2094 2.74

9a 600 0.61 6.000 13.33 35.33 1.97 1180 1.55 90.00 15.00 37.78 57.78 5.57 501 0.66

9b 804 0.58 8.100 15.93 43.46 2.35 1889 2.48 208.48 25.93 41.90 71.43 6.18 1288 1.69

10 183 0.79 1.920 17.19 39.06 2.54 464 0.61 37.17 20.31 53.85 79.49 7.94 295 0.39

11 208 0.22 2.250 4.00 22.22 0.59 123 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

12 11 0.13 0.225 4.44 40.00 0.65 7 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

13 177 0.80 2.010 15.92 35.82 2.35 416 0.54 79.26 44.78 33.33 61.11 4.92 390 0.51

14 84 0.44 0.810 4.94 16.05 0.73 61 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

15 99 0.28 0.990 7.07 32.32 1.04 103 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

16 130 0.66 1.320 14.39 31.06 2.12 276 0.36 29.55 22.73 36.67 70.00 5.41 160 0.00

17 1460 0.80 9.750 13.85 31.08 2.04 2982 3.91 336.97 23.08 38.22 55.11 5.64 1899 2.49

18 323 0.83 3.398 20.31 44.73 3.00 967 1.27 180.40 55.85 31.09 46.90 4.58 827 1.08

19 17 0.00 0.300 0.00 10.00 0.00 0 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

20 372 0.76 3.750 31.20 72.00 4.60 1712 2.24 207.58 55.80 43.97 79.81 6.48 1346 1.76

23 361 1.13 3.750 28.53 53.87 4.21 1519 1.99 144.40 40.00 55.33 80.00 8.16 1178 1.54

24 312 0.82 1.800 27.78 61.67 4.10 1278 1.68 103.99 33.33 78.33 96.67 11.55 1201 1.57

25 397 0.93 2.400 22.08 45.83 3.26 1293 1.69 99.25 25.00 75.00 105.00 11.06 1098 1.44

26 22 3.00 0.300 40.00 53.33 5.90 130 0.00 22.00 100.00 40.00 53.33 5.90 130 0.00

30 24 0.00 0.300 0.00 26.67 0.00 0 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

34 14 0.00 0.188 0.00 10.64 0.00 0 0.00 0.00 0.00 0.00 0.00 0.00 0 0.00

Tot/Avg 7765 75.886 2.72 21113 26.72 2218.78 28.57 6.98 15484 19.62
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table A-2. 2005 Wolf Creek Management Area transecting summary.

Colony Size Active 

Ratio

Ha 

Sampled

Active/Ha Total/Ha PD Density 

- Total

PD # Total BFF Rating 

-Total

Ha Good % Good Active/Ha 

- Good

Total/Ha 

- Good

PD Density 

- Good

PD # Good BFF Rating 

- Good

1 1281 0.55 12.600 22.14 40.40 3.27 4183 5.48 457 35.71 46.44 65.56 6.85 3133 4.112 86 2.00 1.125 28.44 42.67 4.19 361 0.47 36 41.33 62.37 73.12 9.20 327 0.433 52 0.50 0.945 6.35 19.05 0.94 49 0.00 0 0.00 0.00 0.00 0.00 0 0.004 36 0.23 0.600 8.33 45.00 1.23 44 0.00 0 0.00 0.00 0.00 0.00 0 0.005 25 0.33 0.300 3.33 13.33 0.49 12 0.00 0 0.00 0.00 0.00 0.00 0 0.006 170 2.37 1.695 26.55 37.76 3.92 666 0.87 90 53.10 40.00 52.22 5.90 533 0.707 44 0.25 0.525 1.90 9.52 0.28 12 0.00 0 0.00 0.00 0.00 0.00 0 0.008 473 1.85 8.183 47.17 72.71 6.96 3290 4.31 386 81.67 53.42 80.51 7.88 3043 3.999a 600 0.83 6.000 18.67 41.17 2.75 1652 2.17 198 33.00 38.89 53.54 5.74 1136 1.499b 804 2.03 8.100 34.81 51.98 5.13 4127 5.41 462 57.41 53.55 69.03 7.90 3645 4.7810 183 1.45 1.920 25.00 42.19 3.69 675 0.88 129 70.31 31.11 51.11 4.59 590 0.7711 208 1.84 2.400 14.58 22.50 2.15 447 0.59 65 31.25 33.33 36.00 4.92 319 0.4212 11 0.00 0.225 0.00 26.67 0.00 0 0.00 0 0.00 0.00 0.00 0.00 0 0.0013 177 1.44 2.010 17.91 30.35 2.64 468 0.61 86 48.51 34.87 48.21 5.14 442 0.5814 84 1.00 0.900 20.00 40.00 2.95 248 0.00 18 21.67 30.77 41.03 4.54 83 0.0015 99 1.70 0.990 34.34 54.55 5.06 501 0.66 60 60.61 46.67 65.00 6.88 413 0.5416 130 4.63 1.320 28.03 34.09 4.13 537 0.70 89 68.18 36.67 43.33 5.41 479 0.6317 1460 2.50 9.750 26.46 37.03 3.90 5697 7.47 741 50.77 40.40 47.47 5.96 4416 5.7918 323 9.13 3.398 42.97 47.68 6.34 2047 2.68 202 62.47 60.31 66.90 8.89 1795 2.3519 17 0.00 0.300 0.00 16.67 0.00 0 0.00 0 0.00 0.00 0.00 0.00 0 0.0020 372 3.52 3.750 52.53 67.47 7.75 2882 3.78 346 93.00 55.63 71.11 8.20 2838 3.7223 361 2.81 3.600 37.50 50.83 5.53 1996 2.62 256 70.83 47.06 60.39 6.94 1775 2.3324 312 1.08 1.800 31.67 61.11 4.67 1457 1.91 156 50.00 60.00 85.56 8.85 1380 1.8125 397 3.00 2.400 30.00 40.00 4.42 1756 2.30 99 25.00 86.67 100.00 12.78 1269 1.6626 22 3.00 0.165 36.36 48.48 5.36 118 0.00 22 100.00 36.36 48.48 5.36 118 0.0030 24 3.50 0.300 23.33 30.00 3.44 83 0.00 0 0.00 0.00 0.00 0.00 0 0.0034 14 0.00 0.188 0.00 21.28 0.00 0 0.00 0 0.00 0.00 0.00 0.00 0 0.00Tot/Avg 7765 75.489 4.29 33308 42.91 3898 50.19 6.92 27734 36.10
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Table A-3. 2006 Wolf Creek Management Area transecting summary.

Colony Size Active 

Ratio

Ha 

Sampled

Active/Ha Total/Ha PD Density 

- Total

PD # Total BFF Rating 

-Total

Ha Good % Good Active/Ha 

- Good

Total/Ha 

- Good

PD Density 

- Good

PD # Good BFF Rating 

- Good

1 1281 9.41 12.600 44.05 48.73 6.50 8322 10.91 854 66.67 61.19 67.26 9.02 7707 10.102 86 8.83 0.743 71.33 79.41 10.52 905 1.19 69 80.81 88.33 88.33 13.03 905 1.193 52 27.00 0.945 28.57 28.57 4.21 219 0.00 27 51.58 55.38 55.38 8.17 219 0.004 36 2.71 0.600 31.67 43.33 4.67 168 0.00 18 50.00 63.33 66.67 9.34 168 0.005 25 4.00 0.300 26.67 33.33 3.93 98 0.00 17 66.67 42.67 42.67 6.29 105 0.006 170 20.67 1.935 64.08 67.18 9.45 1607 2.11 144 84.50 71.56 75.23 10.55 1516 1.997 44 14.00 0.525 26.67 26.67 3.93 173 0.00 25 57.14 40.00 40.00 5.90 148 0.008 473 23.47 4.793 73.44 76.57 10.83 5123 6.71 455 96.09 76.22 78.83 11.24 5109 6.709a 600 8.72 6.000 52.33 58.33 7.72 4630 6.07 499 83.13 62.56 68.97 9.23 4602 6.039b 804 6.69 8.100 45.43 52.22 6.70 5387 7.06 610 75.93 55.45 62.11 8.18 4992 6.5410 183 82.00 1.890 43.39 43.39 6.40 1171 1.53 139 76.20 52.78 52.78 7.78 1085 1.4211 208 8.75 2.250 31.11 34.67 4.59 954 1.25 111 53.33 48.33 52.50 7.13 791 1.0413 177 15.00 2.010 29.85 31.84 4.40 779 1.02 106 59.70 45.83 47.50 6.76 714 0.9417 1460 14.22 9.450 40.63 43.49 5.99 8748 11.47 1043 71.43 51.41 53.78 7.58 7907 10.3618 323 16.38 3.398 38.55 40.91 5.69 1836 2.41 212 65.56 52.53 54.32 7.75 1640 2.1520 372 7.41 3.750 63.20 71.73 9.32 3467 4.54 365 98.00 64.22 72.93 9.47 3453 4.5323 361 7.09 3.600 65.00 74.17 9.59 3460 4.54 331 91.67 69.70 78.79 10.28 3402 4.4624 312 6.06 1.800 53.89 62.78 7.95 2480 3.25 260 83.33 61.33 71.33 9.04 2352 3.0825 397 18.67 2.100 53.33 56.19 7.86 3122 4.09 170 42.86 107.78 111.11 15.89 2705 3.54Tot/Avg 7364 66.789 7.15 52649 68.15 5455 74.06 9.08 49520 64.07* Towns 12, 14, 15, 16, 19, 26, 30, and 34 were not transected in 2006. These colonies total 401 hectares, or 5% of the prairie dog acreage in Wolf Creek.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

27

APPENDIX B: SUMMARY OF BLACKFOOTED FERRET RELEASE DATA

From the Wolf Creek 

Management Area, 2001–2006

Key to black-footed ferret origin and precondition site facilities:

BP Browns Park, Colorado

CMZ Cheyenne Mountain Zoo, Colorado

CRC National Zoo Conservation and Research Center, Virginia

FCC National Black-footed Ferret Conservation Center, Wyoming/Colorado

LZG Louisville Zoological Garden, Kentucky

PHZ Phoenix Zoo, Arizona

SD-WB Conata Basin, South Dakota (wild-born)

TESF Turner Endangered Species Fund, New Mexico

TOR Toronto Zoo, Ontario, Canada

*All release locations are taken in the North American Datum of 1927.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table B-1. 2001 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

2150 F A 116*249*391 039*077*028 FCC BP 11/15/01 12 - -2399 F A 029*112*079 042*826*615 FCC BP 11/15/01 12 - -2427 F A 028*627*041 042*819*585 LZG BP 11/15/01 12 - -2453 F A 028*848*855 029*112*603 FCC BP 11/15/01 12 - -2474 F A 029*115*568 042*780*600 LZG BP 11/15/01 12 - -2560 F A 029*054*813 042*317*846 FCC BP 11/15/01 12 - -2600 F A 029*116*304 043*115*604 LZG BP 11/15/01 12 - -3474 M K 042*783*837 043*317*846 FCC BP 11/15/01 12 - -3518 M K 048*817*095 048*547*770 FCC FCC 11/15/01 12 - -3519 M K 048*562*603 048*380*781 FCC FCC 11/15/01 12 - -3525 M K 048*558*109 048*568*354 FCC FCC 11/15/01 12 - -3541 M K 048*535*081 048*794*876 FCC FCC 11/23/01 12 - -3546 F K 042*768*783 049*061*569 FCC FCC 11/15/01 12 - -3553 M K 048*524*850 048*559*611 FCC FCC 11/15/01 12 - -3554 F K 048*581*028 048*570*005 FCC FCC 11/15/01 12 - -3560 M K 048*552*357 048*585*081 FCC FCC 11/15/01 12 - -3561 M K 048*773*293 048*770*346 FCC FCC 11/23/01 12 - -3565 F K 048*580*616 048*784*083 FCC FCC 11/15/01 12 - -3658 M K 040*617*852 042*798*604 CMZ BP 11/15/01 12 - -3659 M K 039*080*034 039*124*575 CMZ BP 11/15/01 12 - -3660 M K 042*846*895 043*272*052 CMZ BP 11/15/01 12 - -3675 M K 042*793*859 043*315*367 LZG BP 11/15/01 12 - -3677 M K 042*810*315 042*817*792 LZG BP 11/15/01 12 - -3684 M K 043*301*017 042*843*623 LZG BP 11/15/01 12 - -3685 F K 042*825*332 040*616*546 LZG BP 11/15/01 12 - -3686 F K 040*605*533 042*872*322 LZG BP 11/15/01 12 - -3690 M K 043*110*572 043*315*851 LZG FCC 11/15/01 12 - -3693 F K 042*842*263 042*848*035 LZG FCC 11/15/01 12 - -P245 F K 040*583*571 040*583*533 BP BP 11/23/01 12 - -P246 M K 040*597*513 040*586*566 BP BP 11/23/01 12 - -P252 M K 040*581*340 040*530*351 BP BP 11/23/01 12 - -P254 F K 040*523*084 040*583*342 BP BP 11/15/01 12 - -P255 F K 030*821*121 031*001*023 BP BP 11/15/01 12 - -P256 F K 031*056*811 030*827*588 BP BP 11/15/01 12 - -P258 F K 030*843*843 030*851*341 BP BP 11/15/01 12 - -
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Table B-2. 2002 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

2334 F A 029*110*564 043*121*296 LZG BP 8/15/02 12 711339 44673762346 F A 114*549*493 049*057*569 FCC FCC 11/19/02 12 703346 44556742552 F A 042*838*809 029*078*032 TOR BP 11/7/02 12 703369 44557322651 F A 029*025*092 122*155*183 TOR BP 10/17/02 12 716748 44629852958 F A 032*626*032 122*559*263 TOR BP 10/17/02 12 709851 44613873000 M A 032*614*841 032*627*548 PHZ BP 8/22/02 12 711463 44670973039 F A 032*624*852 032*620*074 PHZ BP 8/22/02 12 711463 44670973060 F A 032*619*301 048*542*537 CRC FCC 8/22/02 12 711165 44675613715 M K 042*880*124 048*794*845 TOR FCC 8/15/02 12 711192 44675573716 F K 043*261*848 048*552*893 TOR FCC 8/15/02 12 711117 44679623770 M K 056*847*323 057*081*017 FCC FCC 11/7/02 12 703684 44560083771 M K 057*368*614 057*545*625 FCC FCC 11/7/02 12 703552 44559713772 M K 057*549*037 057*276*884 FCC FCC 11/7/02 12 703471 44557883773 M K 057*374*866 057*345*380 FCC FCC 11/7/02 12 703583 44561833774 F K 057*046*096 057*356*629 FCC FCC 11/7/02 12 703454 44560853775 F K 057*052*296 057*578*834 FCC FCC 11/7/02 12 703317 44559643776 F K 056*858*812 056*879*056 FCC FCC 11/7/02 12 703306 4455591P280 M K 055*607*887 056*627*830 BP BP 10/17/02 12 710106 4461358P281 M K 056*638*293 055*627*770 BP BP 10/17/02 12 716398 4464252P284 F K 056*831*891 056*327*061 BP BP 10/17/02 12 716523 4463456P285 F K 056*772*366 055*827*771 BP BP 10/17/02 12 716905 4464376P288 F K 055*831*601 055*828*270 BP BP 10/17/02 12 717757 4462541P303 F K 055*616*099 056*095*348 BP BP 10/17/02 12 717547 4462516P305 F K 057*033*868 057*282*323 BP BP 10/17/02 12 716668 4463282P315 M K 040*526*064 057*001*373 BP BP 10/17/02 12 717519 4461988P316 F K 057*315*639 057*051*260 BP BP 10/17/02 12 716902 4462752P317 F K 056*874*790 057*044*879 BP BP 10/17/02 12 717546 4461867P325 F K 056*851*551 056*890*627 BP BP 11/19/02 12 704013 4457486
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Figure B-1. Black-footed ferret release locations within the Wolf Creek Management Area – 2002.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

31

Table B-3. 2003 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

03-051 F K 046*011*600 046*029*313 SD SD-WB 10/10/03 12 716529 446444103-056 M K 046*113*280 046*326*030 SD SD-WB 10/10/03 12 716634 446257903-062 F K 046*372*000 046*017*360 SD SD-WB 10/10/03 12 716958 446238703-079 M K 046*893*845 046*286*578 SD SD-WB 10/10/03 12 716478 446262003-093 F K 046*264*867 046*295*857 SD SD-WB 10/10/03 12 717437 446440703-094 M K 046*295*280 046*295*290 SD SD-WB 10/10/03 12 716998 446256503-103 M K 046*076*521 046*391*338 SD SD-WB 10/10/03 12 716774 446269503-113 M K 054*539*301 055*282*297 SD SD-WB 10/10/03 12 716776 446302403-134 M K 055*058*118 054*033*871 SD SD-WB 10/10/03 12 716985 446436803-135 F K 054*020*845 054*534*328 SD SD-WB 10/10/03 12 716743 44628803175 F A 056*857*336 048*790*621 FCC TESF 9/16/03 12 708665 44566503198 F A 027*521*288 057*276*058 FCC BP 8/16/03 12 711731 44626303199 F A 027*370*011 057*270*345 FCC BP 8/16/03 12 708641 44659123204 F A 040*524*580 056*869*637 FCC BP 8/16/03 12 716405 44644033236 F A 039*080*086 057*551*782 FCC BP 8/16/03 12 716108 44647163259 M A 049*073*328 010*353*824 TOR TESF 9/16/03 12 705848 44550593271 F A 010*287*099 010*575*637 TOR TESF 9/16/03 12 707305 44591593272 F A 011*070*258 011*047*016 BP BP 10/14/03 12 713693 44642073276 F A 039*069*101 039*068*013 TOR BP 8/16/03 12 716176 44627253279 F A 039*098*556 039*074*361 TOR BP 10/14/03 12 711703 44611873285 F A 039*104*800 039*256*344 TOR BP 8/16/03 12 708791 44653083298 M A 039*101*292 056*868*376 PHZ TESF 9/16/03 12 706748 44560503301 F A 039*064*825 057*373*100 PHZ TESF 9/16/03 12 707539 44551363471 F A 041*012*527 042*791*874 FCC BP 10/14/03 12 715611 44619523610 F A 042*870*771 041*009*532 CRC BP 9/24/03 12 711261 44676223687 F A 042*839*337 043*311*603 LZG BP 10/30/03 12 - -3981 M K 047*265*372 057*540*550 PHZ TESF 9/16/03 12 707015 44575013983 F K 047*514*059 056*855*276 PHZ TESF 9/16/03 12 706992 44550023987 F K 047*370*779 057*052*882 PHZ TESF 9/16/03 12 706520 44587523989 F K 047*342*602 057*003*848 PHZ TESF 9/16/03 12 706722 44573683990 M K 048*532*788 057*342*283 PHZ TESF 9/16/03 12 708720 44563143992 F K 056*888*543 057*058*256 PHZ TESF 9/16/03 12 706239 44551683993 F K 057*522*117 056*894*059 PHZ TESF 9/16/03 12 704992 44548563994 M K 042*771*857 042*805*043 CRC CRC 9/16/03 12 707257 4455342
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Table B-3. 2003 Wolf Creek black-footed ferret release data (continued).

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

3995 M K 043*105*564 042*856*105 CRC CRC 9/16/03 12 706634 44562933996 M K 042*797*010 043*314*895 CRC CRC 9/16/03 12 707371 44588773997 F K 042*846*636 043*115*276 CRC CRC 9/16/03 12 707248 44574093998 F K 043*289*042 057*585*598 CRC CRC 9/16/03 12 706530 44561563999 F K 042*789*857 042*833*803 CRC CRC 9/16/03 12 706789 44561764000 M K 057*351*526 056*847*349 FCC FCC 9/16/03 12 706928 44593944001 M K 057*364*784 056*856*260 FCC FCC 9/16/03 12 706901 44590854002 F K 057*266*553 057*257*123 FCC FCC 9/16/03 12 706550 4455948P385 F K 040*531*789 040*550*548 BP BP 9/24/03 12 713736 4464228P386 F K 040*604*045 040*538*341 BP BP 9/24/03 12 711675 4461640P387 M K 040*526*592 057*057*059 BP BP 10/14/03 12 711893 4460579P388 M K 040*601*061 040*553*882 BP BP 10/14/03 12 715537 4461804P389 F K 040*348*021 040*615*341 BP BP 10/14/03 12 708592 4465642P390 F K 040*613*376 040*588*801 BP BP 10/14/03 12 711321 4467802P391 M K 040*584*808 040*539*355 TOR BP 10/14/03 12 710731 4466738P392 M K 040*343*555 040*589*866 BP BP 10/14/03 12 715705 4461389P393 M K 040*589*080 040*614*281 BP BP 10/14/03 12 708181 4465824P394 M K 040*604*884 040*542*575 BP BP 10/14/03 12 713815 4464543P395 F K 040*591*880 040*604*053 BP BP 10/14/03 12 715612 4462120P396 F K 040*583*325 040*580*553 BP BP 10/14/03 12 710744 4466589P397 F K 040*535*347 040*580*561 BP BP 10/14/03 12 708645 4465986P399 M K 040*529*831 040*597*047 BP BP 10/14/03 12 715769 4461389P400 M K 040*597*067 040*615*871 BP BP 10/14/03 12 713815 4464543P401 F K 040*614*863 040*535*321 BP BP 10/14/03 12 - -P402 F K 040*609*782 040*608*855 BP BP 10/14/03 12 711729 4461981P404 M K 040*528*870 040*564*871 BP BP 10/30/03 12 706726 4456129P405 M K 040*546*281 040*600*371 BP BP 11/19/03 12 704996 4454897P406 F K 040*595*116 040*559*357 BP BP 10/30/03 12 706743 4458890P407 F K 040*618*545 040*604*569 BP BP 10/30/03 12 706850 4456269
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Figure B-2. Black-footed ferret release locations within the Wolf Creek Management Area – 2003.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table B-4. 2004 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

3499 F A 042*836*037 069*359*314 FCC BP 10/6/04 12 717442 44638564383 M K 069*053*849 070*001*068 FCC BP 10/6/04 12 717326 44608204384 M K 068*882*049 069*336*614 FCC BP 10/6/04 12 715569 44618594385 M K 069*034*605 069*083*872 FCC BP 10/6/04 12 708830 44583424386 F K 069*532*027 069*559*288 FCC BP 10/6/04 12 706895 44576874387 F K 069*598*053 069*050*541 FCC BP 10/6/04 12 711621 44581904389 M K 069*084*627 069*336*379 FCC BP 10/6/04 12 716413 44620974390 M K 069*369*593 069*343*578 FCC BP 10/6/04 12 711378 44581354391 F K 040*527*880 069*035*604 FCC BP 10/6/04 12 716670 44621474392 F K 069*035*872 069*342*631 FCC BP 10/6/04 12 707276 44549374393 F K 069*829*093 069*354*125 FCC BP 10/6/04 12 709726 44576724394 M K 069*054*866 068*824*623 FCC BP 10/6/04 12 717823 44627714395 M K 070*111*582 068*883*111 FCC BP 10/6/04 12 709651 44576274397 F K 070*030*020 069*038*104 FCC BP 10/6/04 12 711974 44552634400 M K 069*331*842 069*053*599 FCC BP 10/6/04 12 709601 44579864404 M K 069*338*602 069*057*623 FCC BP 10/6/04 12 710206 44560224405 M K 068*830*316 069*034*860 FCC BP 10/6/04 12 707139 44550144406 M K 069*041*620 069*032*887 FCC BP 10/6/04 12 711711 44582574410 M K 069*340*520 069*363*011 FCC BP 10/6/04 12 706796 44576974411 F K 068*893*114 069*105*027 FCC BP 10/6/04 12 715354 44607534412 F K 069*330*840 069*033*342 FCC BP 10/6/04 12 708865 44587864413 F K 069*081*840 068*886*579 FCC BP 10/6/04 12 711723 44553824414 F K 069*256*854 068*842*326 FCC BP 10/6/04 12 710500 44562744445 M K 069*807*553 077*100*803 FCC FCC 10/22/04 12 710863 44654714452 M K 069*076*092 069*354*798 FCC FCC 10/8/04 12 706492 44588034457 F K 068*830*561 068*828*804 FCC FCC 10/8/04 12 711108 44683914472 M K 069*823*263 076*084*597 FCC FCC 10/22/04 12 710044 44616294481 M K 070*020*817 069*065*628 FCC FCC 10/8/04 12 706501 44587544485 M K 070*282*799 076*876*273 FCC FCC 10/22/04 12 710688 44652504495 M K 065*867*512 077*095*007 FCC FCC 10/22/04 12 710276 44607074500 M K 066*005*835 069*364*890 FCC FCC 10/8/04 12 706715 44590304501 M K 070*296*272 069*074*024 FCC FCC 10/8/04 12 711264 44675884507 F K 069*877*565 069*338*290 FCC FCC 10/8/04 12 706719 44588674523 F K 066*346*061 076*884*834 FCC FCC 10/22/04 12 708907 4461258
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table B-4. 2004 Wolf Creek black-footed ferret release data (continued).

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

4539 F K 066*347*337 068*842*088 FCC FCC 10/8/04 12 711181 44677584634 F K 076*836*052 069*272*095 FCC FCC 11/16/04 12 711877 44609684636 M K 077*104*058 069*336*329 FCC FCC 11/16/04 12 709648 44614594671 M K 077*007*062 069*267*070 FCC FCC 11/16/04 12 711725 44624474680 M K 077*111*335 069*529*314 FCC FCC 11/16/04 12 711778 44619094736 M K 077*087*836 069*792*583 FCC FCC 11/16/04 12 706721 44589394739 M K 076*783*575 068*829*861 FCC FCC 11/16/04 12 709847 44613204741 F K 076*818*586 069*025*283 FCC FCC 11/16/04 12 706721 44589384745 F K 077*120*290 068*843*557 FCC FCC 11/16/04 12 709896 44613164757 F K 077*059*273 069*351*273 FCC FCC 11/16/04 12 711617 4462433
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Figure B-3. Black-footed ferret release locations within the Wolf Creek Management Area – 2004.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table B-5. 2005 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

4845 M K 040*257*340 107*313*015 FCC BP 10/13/05 12 716977 44643724847 M K 041*381*541 107*265*515 FCC BP 10/13/05 12 716925 44645374854 F K 041*362*049 107*112*119 FCC BP 10/13/05 12 716966 44642284855 M K 041*326*561 107*258*008 FCC BP 10/13/05 12 706851 44593534859 M K 041*319*839 107*304*824 FCC BP 10/13/05 12 707110 44590454868 M K 041*361*849 107*298*033 FCC BP 10/13/05 12 707417 44589274875 M K 040*534*343 107*280*546 FCC BP 10/19/05 12 717186 44592524883 F K 041*335*582 107*265*632 FCC BP 10/19/05 12 717843 44588814884 F K 041*338*553 107*119*029 FCC BP 10/19/05 12 717225 44594974895 M K 040*595*306 107*306*071 FCC BP 10/19/05 12 715333 44638914898 F K 040*607*127 107*120*346 FCC BP 10/19/05 12 715124 44632934899 M K 040*580*263 107*127*383 FCC BP 10/19/05 12 717546 44588304911 M K 040*598*268 107*296*886 FCC BP 10/19/05 12 714943 44637324934 F K 041*517*828 107*270*354 FCC BP 10/26/05 12 717398 44596554944 M K 107*285*090 107*289*629 CMZ BP 10/26/05 12 717586 44588534948 M K 041*337*054 107*122*768 FCC BP 10/26/05 12 717294 44643164951 F K 041*291*001 107*273*307 FCC BP 10/26/05 12 718219 44633574954 M K 107*121*294 107*266*614 CMZ BP 10/26/05 12 703222 44555114997 M K 041*314*559 107*279*591 FCC BP 11/2/05 12 703425 4455486
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Figure B-4. Black-footed ferret release locations within the Wolf Creek Management Area – 2005.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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Table B-6. 2006 Wolf Creek black-footed ferret release data.

Studbook # Sex Age Head Chip Rear Chip Origin Precondition Site Release Date

Release Location (UTM)

Zone Easting Northing

4008 F A 057*344*620 056*859*326 TOR BP 9/26/06 12 713910 44567515123 M K 081*377*294 081*377*531 LZG BP 10/24/06 12 710258 44558405139 M K 107*278*533 107*305*320 FCC BP 9/26/06 12 716676 44587305144 M K 107*122*628 107*112*307 FCC BP 10/8/06 12 706733 44588645153 F K 081*087*782 057*127*048 FCC BP 9/26/06 12 717200 44592375167 M K 073*621*841 056*870*616 FCC BP 9/26/06 12 714079 44562655172 M K 099*090*858 097*824*564 FCC BP 9/26/06 12 715347 44570475177 F K 074*055*114 107*293*043 FCC BP 9/26/06 12 715137 44633015179 M K 098*606*839 098*875*795 FCC BP 9/26/06 12 715343 44639715207 M K 042*788*062 081*378*831 LZG BP 10/24/06 12 715385 44567445212 F K 081*377*296 081*378*891 LZG BP 10/24/06 12 703543 44556795219 M K 098*789*065 099*092*588 FCC BP 10/8/06 12 710578 44564295221 M K 098*886*023 091*805*366 FCC BP 10/8/06 12 703957 44560375235 F K 102*581*009 081*377*006 CMZ BP 10/24/06 12 716263 44625235237 M K 098*026*117 098*363*872 FCC BP 10/8/06 12 706444 44587135247 M K 098*878*799 098*339*106 FCC BP 10/8/06 12 703166 44554055248 F K 098*090*066 098*637*592 FCC BP 10/8/06 12 703209 44555065255 F K 107*112*854 107*263*559 FCC BP 10/24/06 12 716603 44622425300 M K 107*110*376 081*377*280 LZG BP 10/24/06 12 714285 44571885330 M K 107*109*259 081*379*016 LZG BP 10/24/06 12 718562 44595925340 M K 098*001*259 081*377*519 LZG BP 10/24/06 12 717422 44598125414 M K 074*083*816 073*355*532 FCC BP 10/24/06 12 716415 44624105425 M K 074*084*316 073*837*891 FCC BP 10/24/06 12 718356 44595125431 F K 073*872*113 074*114*808 FCC BP 11/7/06 12 709414 44577845436 F K 073*328*074 074*266*024 FCC BP 11/7/06 12 716971 44647485439 M K 098*033*527 074*041*373 FCC BP 11/7/06 12 709302 44575655441 F K 073*633*845 073*310*845 FCC BP 11/9/06 12 716395 44634045442 F K 073*814*546 074*310*257 FCC BP 11/7/06 12 716420 4464611
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Figure B-5. Black-footed ferret release locations within the Wolf Creek Management Area – 2006.
A REVIEW OF BLACK-FOOTED FERRET REINTRODUCTION IN NORTHWEST COLORADO, 2001–2006

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LITERATURE CITED

Anderson, E., S.C. Forrest, T.W. Clark, and 

L. Richardson. 1986. Paleobiology, 

biogeography, and systematics of the 

black-footed ferret, Mustela nigripes

(Audubon and Bachman), 1851. Great 

Basin Naturalist Memoirs 8:11-62.

Barnes, A.M. 1993. A review of plague and 

its relevance to prairie dog populations and the black-footed ferret. In J.L. 

Oldemeyer, D.E. Biggins, B.J. Miller, and 

R. Crete (editors). Management of prairie 

dog complexes for the reintroduction 

of the black-footed ferret. Biological 

Report 13, U.S. Fish and Wildlife Service, 

Washington, DC. p. 28-37.

Biggins, D.E, B.J. Miller, L.R. Hanebury, B. 

Oakleaf, A.H. Farmer, R. Crete, and A. 

Dood. 1993. A technique for evaluating black-footed ferret habitat. In J.L. 

Oldemeyer, D.E. Biggins, B.J. Miller, and 

R. Crete (editors). Management of prairie 

dog complexes for the reintroduction 

of the black-footed ferret. Biological 

Report 13, U.S. Fish and Wildlife Service, 

Washington, DC. p. 73-88.

Biggins, D.E., J.L. Godbey, L.R. Hanebury, B. 

Luce, P.E. Marinari, M.R. Matchett, and 

A. Vargas. 1998. The effect of rearing 

methods on survival of reintroduced 

black-footed ferrets. Journal of Wildlife 

Management 62:643-653.

Biggins, D.E., J.M. Lockhart, and J.L. Godbey. 

2006a. Evaluating habitat for black-footed ferrets: revision of an existing model. 

In J.E. Roelle, B.J. Miller, J.L. Godbey, 

and D.E. Biggins (editors). Recovery of 

the black-footed ferret: progress and 

continuing challenges. U.S. Geological 

Survey Scientific Investigations Report 

2005-5293. Reston, VA. p. 143-150.

Biggins, D.E., J.L. Godbey, M.R. Matchett, 

and T.M. Livieri. 2006b. Habitat preferences and intraspecific competition in 

black-footed ferrets. In J.E. Roelle, B.J. 

Miller, J.L. Godbey, and D.E. Biggins (editors). Recovery of the black-footed ferret: 

progress and continuing challenges. U.S. 

Geological Survey Scientific Investigations Report 2005-5293. Reston, VA. p. 

129-140.
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