Once thought extinct, ferret bounces back

Black-footed ferrets, among the most endangered mammals in North America, are staging a comeback in the Shirley Basin of Wyoming, scientists said Thursday.

A decade after they were given up for goners, the area’s ferret population has grown from five to an estimated 220, according to a report in the journal Science.

“We hear so much about how the Endangered Species Act is broken and animals go extinct. But when given a chance and when people work together, endangered species can recover,” said Jonathan Proctor, of Defenders of Wildlife, who was not connected with the study.

Lead author Martin Grenier, of Wyoming Game and Fish and the University of Wyoming, said it was unclear why the ferret had made such a comeback.

“We need to look back within ourselves and say, ‘OK, what piece of the puzzle are we missing?’ ” he said. “Why are we not seeing this kind of pattern at all our sites?” Black-footed ferrets, the only species of ferret native to North America, have been listed as endangered since the original version of the act in 1967.

The ferret is nocturnal and secretive, and it preys almost exclusively upon prairie dogs. Both animals once lived throughout much of central North America, but habitat destruction and the poisoning of prairie dogs drastically reduced their numbers.

Ferrets were thought to be extinct from 1974 to 1981. A small population was later discovered near Meeteetse, Wyo., and authorities removed the animals to start a captive breeding program.

The ferrets were reintroduced to the Shirley Basin in 1991 and later to about a dozen other sites. No ferrets were transplanted to the Shirley Basin after 1994.

Only one location – the Conata Basin in South Dakota – initially proved successful. Sylvatic plague took a toll in the Shirley Basin. After Wyoming Game and Fish workers found only five ferrets in 1997, monitoring became sporadic. But in 2003, 52 animals were found, and the numbers have gone up exponentially.

“We shouldn’t be giving up on things too early,” said Michael Lockhart, coordinator of the U.S. Fish and Wildlife Service’s black-footed-ferret recovery.

Grenier suspects that a few ferrets were able to find refuge from the plague in the large habitat of the Shirley Basin and went on to reproduce rapidly when conditions improved.