The black-footed ferret (Mustela nigripes) is considered to be the most endangered land mammal in North America. Thought to be extinct in the 1970s, a small colony of this small member of the weasel family was found on a ranch near Meteetse, Wyoming. Canine distemper killed all but eighteen ferrets in the colony. The survivors were trapped and protected by the U.S. Fish and Wildlife Service and became part of a captive breeding program in U.S. and Canadian zoos.

The black-footed ferret is a prairie resident that is dependent upon extensive prairie dog colonies for survival. Depletion of prairie dog towns throughout the twentieth century has lead to the near extinction of this ferret. Captive-bred ferrets were reintroduced in Badlands National Park in 1994. Park staff are encouraged by the presence of wildborn kits (young ferrets), some of which are now producing young of their own.