The black-footed ferret was once considered the most endangered mammal in the United States, but recently much progress has been made toward its recovery.
Black-footed ferrets are members of the weasel family (Mustelidae), a distinction they share with weasels, martens, fishers, otters, minks, wolverines, and skunks. Larger than a weasel, black-footed ferrets are long, slender-bodied animals similar in size to a mink. The species is characterized by a brownish-black mask across the face, a brownish head, black feet and legs, and a black tip on the tail. The fur is short and could be described as pale yellow buff, becoming lighter on the underside of the body. The middle of the back has brown-tipped guard hairs that create the appearance of a dark saddle.
The black-footed ferret may look a little like the ferrets found in pet stores, but it is actually a different species. Both belong to the weasel family, but the ferrets sold as pets evolved in Europe, while the endangered black-footed ferret evolved in North America.
Possibly the black-footed ferret was never abundant, but its underground, nocturnal habits make it difficult for biologists to know this for certain. First described by naturalists John Audubon and John Bachman in 1851, it was not sighted again for 25 years.
Ferrets were once found throughout the Great Plains, from Texas to southern Saskatchewan, Canada. Their range extended from the Rocky Mountains eastward through the Dakotas and south through Nebraska, Kansas, Oklahoma, and Texas. Where prairie dogs were found, so were black-footed ferrets. Ferrets eat prairie dogs and live in the prairie dog's burrow.
Typical behavior of wild ferrets revolves around the prairie dog towns. Wild ferrets hunt prairie dogs at night, but occasionally they are active above ground during the day. This is especially true of the female ferrets hunting to feed their young. In search of prey, they move along in loping bounds from one burrow to the next. When it makes a kill, a ferret may drag a prairie dog some distance to a home burrow where it may devour it below ground, or drag fresh prey to burrows in which they have their young.
Black-footed ferrets produce four or five young once each year. Born in May or June, the young do not come above ground until they are 6 weeks old. The mother and young remain together until about mid-August. At that time, the female begins to separate siblings into different burrows. From August through early September the young become increasingly solitary. By early October they are able to take care of themselves.
As the prairies were settled, prairie dogs competed with livestock for the available forage. This resulted in intensive efforts to eliminate these "pest rodents." Without the prairie dog, the black-footed ferret had no source of food, and its populations seriously declined as a result.
The black-footed ferret was listed as an endangered species in 1967 (under a law that preceded the Endangered Species Act of 1973), meaning it was considered in danger of becoming extinct in all or a significant portion of its range. By 1972, the black- footed ferret was in fact believed to be extinct. From 1972 through 1981, many ferret sightings were reported, but no black- footed ferrets were found. Then in 1981, a dog killed an unusual animal on a ranch in Wyoming. The rancher took it to a taxidermist who recognized it as a black-footed ferret. This led to the discovery of a small ferret population near Meeteetse, Wyoming, in 1981. The population increased from 1981 through 1984. At its peak in 1984, nearly 130 ferrets were counted.
In October 1985, the Wyoming Game and Fish Department, in cooperation with the U.S. Fish and Wildlife Service, captured six black-footed ferrets to start a captive breeding population at the Department's Sybille Wildlife Research and Conservation Education Center near Wheatland, Wyoming. Shortly after their capture, all of these ferrets died of canine distemper. Six additional ferrets were then captured, and these remained healthy. During the fall of 1986 and the spring of 1987, the last of 18 known wild black-footed ferrets were taken from the wild and placed in the captive breeding facility. This captive population has increased to more than 500 captive black-footed ferrets.
The goal of the captive breeding program is to establish 240 breeding adults in captivity, while continuing the return of ferrets to the wild. In an effort to protect the ferrets from any one catastrophic event, the captive population was divided. In addition to the Sybille colony, breeding populations have been established at the National Zoo's Conservation and Research Center in Front Royal, Virginia; the Henry Doorly Zoo in Omaha, Nebraska; the Cheyenne Mountain Zoological Park in Colorado Springs, Colorado; the Phoenix Zoo in Phoenix, Arizona; and the Louisville Zoological Garden in Louisville, Kentucky.
The future looks brighter for the black-footed ferret. Reintroduction began in 1991 with the release of a group of ferrets into the Shirley Basin of Wyoming. Since then, 189 ferrets have been released there. While there is a high mortality rate among these captive-born animals, two litters born in the wild indicate that the reintroduced population has taken hold.
Two new reintroduction sites in Montana and South Dakota have been identified, where at least 40 to 50 ferrets per year will be released at each site for 5 years. After the fifth year, the sites should be self-sustaining.
Areas in Utah, Colorado, and Arizona also have been identified as suitable release sites. To be considered suitable for ferret reintroduction, an area must be very large -- at least 10,000 acres for each ferret family. The area must be relatively free of diseases, particularly of canine distemper and plague, that could wipe out an entire colony. And, the public must support the presence of the black-footed ferrets. To this end, biologists work closely with landowners to work out compromises that benefit the ferret and landowners.
National goals to recover the species are to establish 10 free-ranging populations of black-footed ferrets, spread over the widest possible area within their former range. Each of these populations will have 30 or more breeding adults. It is hoped that 1,500 free-ranging black-footed ferrets will be established in the wild by the year 2010.
If these and future efforts are successful, black-footed ferrets may soon by playing an important role in the dynamics of wild prairie dog towns once again.