Black-footed Ferret

Mustela nigripes

Description

The black-footed ferret, Mustela nigripes, is a short-legged, slender-bodied weasel that grows to an adult length of about 1.5 ft (45 cm). The fur over most of its body is pale yellow. The throat and belly are nearly white. The face is masked with dark fur, and the feet and tail are very dark. The coat lightens somewhat during winter.

Behavior

The ferret is a nocturnal prowler that lives in burrows dug by the prairie dogs on which it preys, making it strongly dependent on this species. Ferrets also eat mice, voles, ground squirrels, gophers, birds, and insects. Male and female ferrets share common burrows in March and April when breeding occurs. The gestation period ranges from 41-45 days, after which a litter of one to five kits is born. In fall, ferrets disperse throughout a larger territory. At this time, mortality is high, especially for males. Ferrets are preyed upon by great-horned owls, golden eagles, and coyotes, and probably by badgers, bobcats, and foxes.

Habitat

The black-footed ferret is adapted to the native prairies of the Great Plains. A large expanse of prairie supporting a large population of prairie dogs is required to support very small numbers of ferrets. It is estimated that it takes 100-148 acres (40-60 hectares) of prairie dog colony to support one black-footed ferret.

Distribution

This ferret formerly ranged in the Great Plains from Alberta, Canada, south through the intermontane regions of the interior Rocky Mountains and the Southwestern United States. In the 1800s, the ferret was widely distributed in low densities in 10 states: Montana, Wyoming, the Dakotas, Nebraska, Kansas, Colorado, New Mexico, Oklahoma, and northern Texas. It was also found in the extreme eastern portions of Utah and Arizona.

No known wild populations of black-footed ferrets survive, although captive-bred ferrets are being reintroduced to their historic habitat. In March of 1996 for instance, 44 captive-bred ferrets sent to Aubrey Valley, Arizona, for acclimation were released to the wild there between early September and mid November. Additional reintroduction efforts began in Montana and South Dakota in 1994 and have continued through 1996. Ferrets released in these states appear to have had higher survival rates than those in Wyoming and have not been affected by disease to date. Approximately 60 ferrets, including reintroduced captive-born animals and their offspring born in the wild, existed in Montana and South Dakota prior to the release of additional captive-born ferrets in 1996.

A captive breeding population has been maintained at the Sybille Wildlife Research Institute in Wyoming. In 1988, this single captive population was divided into five separate captive subpopulations to prevent the possibility of a single catastrophic event eliminating the entire captive population. In 1991 and 1992, two additional captive subpopulations were established. By 1995, 400 breeding pairs had been established.

Threats

Ranchers and farmers have conducted an extensive and prolonged campaign to rid the Great Plains of prairie dogs, which are considered a pest. Conversion of large tracts of prairie to agricultural land drastically reduced the amount of available prairie dog habitat, and the reduced population was then hunted and poisoned to even lower levels. The black-footed ferret declined in direct proportion to the prairie dog. Because ferret densities are low, a breeding population is spread over many square miles. As overall habitat became more fragmented, the ferret population grew less able to replenish itself. The isolated breeding groups eventually died out.

Conservation and Recovery

Beginning in 1954, the U. S. Fish and Wildlife Service (FWS) and the National Park Service began capturing black-footed ferrets and transferring them to sanctuaries that had large prairie dog populations, such as Wind Cave National Park in South Dakota. These attempts, unfortunately, were unsuccessful because of a limited understanding of the animal's biology and a severe plague of canine distemper that decimated the susceptible ferrets to the point of breeding collapse. The disease exterminated wild populations. Distemper continues to be a concern in captive-breeding and translocation efforts. The first FWS Recovery Plan for this species was completed in 1978, stressing an intensification of research and the establishment of the captive breeding facility at Sybille Wildlife Research Institute. In 1987, the Wyoming Fish and Game Department developed a comprehensive plan for managing the ferret in Wyoming. As a first step, researchers began a systematic survey to locate potential habitat where captive-bred animals could be relocated. Beginning with only 18 surviving animals from the last known wild population at Meeteetse, Wyoming, the captive breeding program produced seven kits in 1987, increasing the known population to 25 ferrets.

By June 1988, 13 of 15 female ferrets at Wyoming's captive breeding facility had produced litters. Some of the largest litters were delivered by ferrets born the previous year. By the end of 1988, 34 kits survived at the facility, bringing the total population to 58 ferrets. The success has continued exponentially. By 1995, the captive population had increased to over 400 animals. Four other breeding facilities were established in 1988 to protect the population from catastrophic destruction at any one location. Since a captive population of 240 breeding adults has been achieved, recovery efforts have advanced to the reintroduction phase of establishing animals back into the wild. FWS, in cooperation with 11 western state wildlife agencies, had by 1995 identified potential ferret reintroduction sites within the historical range of the species. Reintroduction has occurred in a number of states, including Wyoming, Montana, Arizona, and South Dakota. A number of western states are in the process of evaluating additional potential reintroduction sites. Sites are selected for reintroduction by the FWS in coordination with the Black Footed Ferret Interstate Coordinating Committee. Higher ferret survival and productivity rates at the Montana and South Dakota release sites are likely associated with the occurrence of more densely populated black-tail prairie dog (Cynomys ludovicianus ) towns there, as opposed to the white-tailed prairie dog (Cynomys leucurus ) habitats found at the Wyoming reintroduction site, according to FWS. Improved success also may be the result of "preconditioning" the ferrets in large outdoor pens inhabited by prairie dogs. Animals prepared in this manner had significantly higher survival rates 30 days after their release than cage-reared ferrets.

Captive breeding and reintroduction projects are the backbone of the national Black-footed Ferret Recovery Program. Some 20 state and federal agencies, along with several non-governmental organizations, spend about US$1.5 million annually on ferret recovery ventures. Although the program has made substantial strides, the total number of ferrets is still quite small (less than 600), and both captive and reintroduced populations are susceptible to catastrophic events.

Montana, Wyoming, Utah, Colorado, Oklahoma, and South Dakota participate in a ferret reward program sponsored by Wildlife Conservation International. The program offers cash payments for confirmed live ferret sightings in an effort to locate other wild populations. The recovery objective for the black-footed ferret, based on the 1988 FWS Recovery Plan, is to ensure immediate survival of the species by—(a) Increasing the captive population of ferrets to 200 breeding adults by 1991 (achieved); (b) establishing a prebreeding census population of 1,500 free-ranging breeding adults in 10 or more different populations, with no less than 30 breeding adults in each population by 2010; and (c) encouraging the widest possible distribution of reintroduced animals throughout their historic range. When this national objective is achieved, the black-footed ferret will be down-listed to a threatened status, assuming that the extinction rate of established populations remains at or below the rate at which new populations are established for at least five years.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

References

Bogan, M. A. 1985. "Needs and Directions for Future Black-footed Ferret Research." In Anderson and Inkley, eds., Proceedings of the Black-footed Ferret Workshop September 18-19, 1984. Wyoming Game and Fish Department, Cheyenne.

Carpenter, J. W. 1985. "Captive Breeding and Management of Black-footed Ferrets." In Anderson and Inkley, eds., Proceedings of the Black-footed Ferret Workshop September 18-19, 1984.. Wyoming Game and Fish Department, Cheyenne.

Clark, T. W., et al. 1987. "Analysis of Black-footed Ferret Translocation Sites in Montana." Prairie Naturalist, no. 19: 43-56.

Maguire, L. A., 1988. et al. "Black-footed Ferret Recovery in Montana: a Decision Analysis." Wildlife Society Bulletin, 2 (16): 111-120.

Richardson, L., et al. 1987. "Winter Ecology of Black-footed Ferrets at Meeteetse, Wyoming." American Midland Naturalist, no. 117: 225-239.

U.S. Bureau of Land Management. 1986. "Prairie Dog Ecosystem Management Plan—Report #WY-010-WHA-TI4." Cody Resource Area, Wor-land, Wyoming District.

U.S. Fish and Wildlife Service. 1988. "Black-footed Ferret Recovery Plan." U.S. Fish and Wildlife Service, Denver.

Wyoming Game and Fish Department. 1987. "A Strategic Plan for the Management of Black-footed Ferrets in Wyoming." Wyoming Game and Fish Department, Cheyenne.