Over time, scientists decided to collect those last ferrets to try to save them. Only 18 survived. Many scientists were skeptical and worried it was too late to save the species, said David Wildt, now the head of the Center for Species Survival at the Smithsonian Conservation Biology Institute, a branch of the National Zoo.
"Can you go down to as few as 18 animals and be able to bring those animals back?" Wildt recalled wondering at the time. "There aren't a lot of examples of successful reintroduction programs."
The ferret's struggle may surprise those who keep ferrets from Europe as pets. American ferrets used to be common across the Great Plains. At least a half million once lived across 12 states.
Prairie dogs are their main food source, but disease and extermination of prairie dogs, considered a nuisance on land for cows, starved the ferrets.
Thirty years later, the ferret population is on the rise. Zoos in Louisville, Ky., Toronto, Phoenix, Cheyenne, Wyo., 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.
"That has never been done before with respect to endangered species," Wildt said. "Here you have a model, not just in terms of producing animals for reintroduction, but the science."
Still, reintroducing ferrets to the wild sparks controversy in places like Kansas, where residents are angry that protecting the ferret means also protecting prairie dogs that some ranchers want to poison on lands reserved for cattle and crops. A Kansas event to celebrate the ferret's rediscovery this week had to be canceled due to protests.
More than 7,000 ferrets bred in zoos have been released into prairie dog colonies since 1991. There are 19 sites stretching from Canada to Mexico where the ferrets are being reintroduced to the wild. Scientists estimate about 1,000 black-footed ferrets live in the wild today.
First, though, they must make it through ferret boot camp. While accustomed to digging in spacious enclosures in Virginia, the Smithsonian-bred ferrets have much to learn. They will be sent to the National Black-Footed Ferret Conservation Center in Colorado for "boot camp."
The "reintroduction candidates" spend at least 30 days in training. It involves exposing them to underground burrows and similar prairie dog tunnels - and the chance to hunt and kill live prey. The training gives them as much as a 10 times better chance of survival in the wild.
