Once rare black-footed ferrets make comeback

WASHINGTON (Reuters) - The black-footed ferret, once the rarest mammal in the world, has made an astonishing comeback in Wyoming after a captive breeding program, researchers said on Thursday.

An estimated 223 of the weasel-like animals are busy hunting prairie dogs in the Shirley Basin area, the researchers report in this week's issue of the journal Science.

The animals are all descended from seven ferrets rescued in 1986, Martin Grenier of the University of Wyoming and colleagues reported.

"The thing that is neat about this is it shows there's good potential to recover the species. We might be able to make faster progress than we've made in the past 15 years," Grenier said in a telephone interview.

"We'd like to be able to eventually remove that species from the endangered species list. It would be a wonderful conservation success story."

Black-footed ferrets were driven nearly to extinction by two factors: the eradication of their main food source, prairie dogs, by ranchers, and a disease called sylvan plague.

"At one point in time, the black-footed ferret was the most endangered mammal in the world. There were only 18 animals," Grenier said.

These 18 animals were whisked out of Wyoming in 1986 and seven of them were bred at zoos, universities and other centers. Hundreds of the creatures were re-introduced to the wild, but did not survive well. By 1997 only five could be found.

The plague and canine distemper, as well as slow breeding patterns, appeared to doom the reintroduction attempt.

But ranchers supported the efforts, in part because they could tolerate the ferret's prey, the white-tailed prairie dog. Black-tailed prairie dogs are often considered pests and eradicated in other areas.

Now the population of the ferrets, known scientifically as Mustela nigripes, is growing at a rate of 35 percent a year, Grenier's team reported.