for National Geographic News
The black-footed ferret, North America's most endangered mammal, has made a remarkable recovery from the brink of extinction, according to a new study.
A key population of the sleek-bodied predator in Shirley Basin, Wyoming, grew from a low of five in 1997 to more than 220 in 2006, the research found.
The increase marks a rapid rise from a decade ago, when disease nearly decimated the ferrets in Shirley Basin, Wyoming's only recovery site for the animal.
Scientists measured the population by scouring thousands of acres at night using high-powered spotlights.
"We only were able to survey about 14 percent of the total [150,000-acre/60,700-hectare] habitat, so there's a chance that even more ferrets are out there than we documented," said Martin Grenier, a biologist for the Wyoming Game and Fish Department who led the study.
The researchers believe more than 400 ferrets may exist.
If their suspicions are correct, Shirley Basin would be home to the largest ferret colony in the United States, a distinction previously held by South Dakota's Conata Basin (see map of the United States).
The findings are published in tomorrow's issue of the journal Science.
Thanks to Prairie Dogs?
Steven Buskirk, a zoology professor at the University of Wyoming and co-author of the study, said ferret populations generally aren't considered capable of growing so quickly.
He attributes the boom to the area's enormous prairie dog colony. Ferrets dine almost exclusively on the rodents and live in their prey's burrows.
Wyoming is home to white-tailed prairie dogs, a species less persecuted by ranchers than the black-tailed prairie dog found at other ferret recovery sites.
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