Ferreting Out Extinction

Back in the late 1970s, when I worked in the five-stoplight town of Lander, Wyoming, I had a wanted poster over my desk, requesting information leading to the whereabouts of a masked little weasel. The reward was $100, if memory serves.

The posters had been distributed by biologists Tim Clark and Dean Biggins in pursuit of the elusive black-footed ferret, Mustela nigripes, North America’s most endangered mammal. In 1979, the last known ferret had died at Patuxent Wildlife Research Center, the final sad stroke in a failed captive breeding program.

Clark and Biggins were looking all across the West to see if any of the animals remained. The posters were one, slightly too cute, effort in this search. But ferrets are hard to find. They spend 80 percent of their life underground in pursuit of their favorite food, the prairie dog.Despite these Old West efforts, there was a long silence on the ferret front. Then in 1981 Lucille Hogg’s dog dropped the carcass of a masked weasel onto the back porch of Lucille’s Cafe in the zero-stoplight town of Meeteetse, Wyoming. Lucille didn’t recognize the animal. (Well, she recognized her dog, of course. I mean the other animal, the dead one.) She showed the carcass to a friend, a Wyoming wildlife official, who identified it as the much-pursued black-footed ferret — doubtless from his resemblance to the wanted poster.

The Clark and Biggins posse rode to the scene. They eventually found 61 individual ferrets in a 30,000-acre prairie dog down near Meeteetse. Better yet, the ferret colony was growing, with nearly 200 ferrets born between 1982 and 1985. This remains the last known wild population of ferrets.

In 1985, plague struck the colony, reducing the number of surviving ferrets to ten. Some biologists and environmentalists wanted to remove them and try captive breeding again. But the earlier captive breeding effort at Patuxent had been a disaster. Another group of equally concerned and committed activists wanted the animals left in the wild, seeing this as the last hope of recovery. Lucille’s Cafe sold t-shirts reading “Live Free or Die.”

Dean Biggins says now, “I don’t think I was convinced of what we should do.”

In the spring of 1986, two females had litters, both sired by a single male, bringing the global population of black-footed ferrets to a little over a dozen animals. Biggins spoke with the scientist who had directed the earlier Patuxent captive breeding effort. He told Biggins that while their initial program had failed, it was because they were working with older, weaker animals. “We had young vigorous animals,” Biggins said. “They didn’t have that.”

But the researchers were convinced that a captive breeding program was the animals’ best bet. They gathered up the remaining ferrets and sent them to Patuxent.

And it didn’t go well. None of the ferrets would breed in the first year. The recovery team was worried because the population was all interrelated — “genetically depauperate,” in the jargon.

But the ferrets began to reproduce in captivity. Eventually the population was large enough to reintroduce them back into the wild.

And that didn’t go very well, either. “With the first reintroductions, we had very high mortality rates,” Biggins said. “We were criticized by environmentalists and animal rights groups who said we were dumping ferrets without any hope of success.”

Many ranchers opposed the reintroductions, too. They don’t have anything against ferrets, per se, but they don’t like prairie dogs. A large population of prairie dogs is needed to support even a small population of ferrets.

But the reintroductions continued in spite of the opposition: In Wyoming’s vast and virtually unpopulated Shirley Basin; In the 43,000 Wolf Creek Management Area in Colorado  southeast of Dinosaur National Monument; and in Colorado Coyote Basin west of Rangely on the Colorado-Utah border.

The last wild ferret in Colorado prior to the 2001 reintroductions was seen in 1946. Now, according to the Division of Wildlife, there are 126 of them in the reintroduction areas.

Despite an almost unbroken string of setbacks, the black-footed ferret appears to be on its way to recovery. In a brief paper in this week’s Science, three Wyoming biologists — Martin Grenier, David McDonald and Steve Buskirk — wrote that the patience with the disappointments have paid off.

The first reintroduced population of the most endangered mammal species in North America, the black-footed ferret, is recovering rapidly in the Shirley Basin of Wyoming after a lag that seemed to portend population extinction.

The ferrets were reintroduced into the Shirley Basin in 1991. About  100 were released in 1992. As the continuing theme of this story suggests, the population immediately crashed to the point that the scientists rarely even checked to see if there were any animals out there between 1997 and 2000.

Now, however, there are at least 200 individuals, and the population has increased by 35 percent a year between 2003 and 2006. The researchers found, “The species potential for rapid population growth seems to contradict the slow life history strategy common to endangered species: low fecundity, high longevity and high age at first reproduction.” Survival in the first year of life is critical to ferrets. With most endangered species, emphasis is given to later adult survival.

Well, so what? It’s just a weasel, right? Rare, and cute, but still a weasel. You’ll probably never even see one.

But the black-footed ferret offers a case study in the effectiveness of the much-maligned Endangered Species Act. The ferret recovery story reads like the Book of Job, with one disaster following another. But the scientists involved slowly accumulated information, made mistakes, learned from them, righted the ship, then took the tentative steps necessary to promote the animal’s long-term survival. This was possible because of the protection offered by the ESA.

The ESA expired in 1992, although it has been funded each year since then. But Congress has not gathered the political will to reauthorize it.

As Peter Gober, a South Dakota field supervisor for the U.S. Fish and Wildlife Service and a leader of ferret recovery in that state, said:

“There is a balance of nature, but it is a balance of nature across continents and centuries, not across the term of a congressman.”

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Dan Whipple

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