Black-footed ferrets are the only ferret species native to North America, with tens of thousands of them living in 12 states across the Great Plains. However, they were thought to have disappeared in the late 1970s until a colony of wild black-footed ferrets was discovered in Wyoming in 1981.
Thirty years later, with the help of scientists, a repopulation effort has proven to be very successful.
Zoos in Louisville, Ky., Toronto, Phoenix, Colorado Springs, Colo., and the Smithsonian's National Zoo joined with the U.S. Fish and Wildlife Service to breed the endangered animals.
The Smithsonian developed the first artificial insemination technique for ferrets, which has produced 139 kits, and scientists are building a ferret sperm bank to maintain the population's genetic diversity.
So far, five kits have been produced using frozen sperm.