The black-footed ferret (Mustela nigripes), one of North America's most endangered mammals. The ferret was thought to be extinct by 1979 but in 1981 a small population was rediscovered. By 1986, the population had fallen to 18 individuals and a captive breeding program was initiated to save the black-footed ferret from extinction. Now, a population of reintroduced ferrets in Colorado is showing signs of gaining foothold, raising the hope that this endangered mammal can again survive in the wild.

Find out more: Endangered Ferrets Gain Colorado Foothold (National Geographic)