The black-footed ferret, Mustela nigripes, is sometimes called "the rarest mammal in North America." In fact, the black-footed ferret was believed to be extinct for quite some time until a wild population of the species was found near Meeteesee, Wyoming in the early 1980s. When that population was threatened by canine distemper in the mid-1980s, the last surviving eighteen individuals were taken into captivity and used to start a captive breeding program. Descendants of those individuals have been released at several sites in the western United States, including the Coyote Basin area of Uintah County, Utah in late 1999. Although the black-footed ferret is a Federally listed endangered species, the re-introduced populations have been classified as "nonessential-experimental" by the U.S. Fish and Wildlife Service. In addition to Utah's re-introduced black-footed ferret population, unconfirmed sightings of naturally occurring ferrets persist throughout eastern Utah.
Black-footed ferrets live in underground prairie dog burrows and eat prairie dogs as their primary food source. The black-footed ferret is, therefore, closely associated with prairie dog towns. For this reason, the major threat to the species is the decimation of prairie dog colonies through plague, poisoning, and habitat loss. The black-footed ferret breeds from March to April, and young are born in about six weeks; average litter size is three. The black-footed ferret is nocturnal.