for National Geographic News
Spring has arrived on the South Dakota prairie, and with it comes a new worry for endangered black-footed ferrets: the return of the plague.
Plague outbreaks appeared for the first time in South Dakota last year just 38 miles (61 kilometers) from the Conata Basin, where the largest group of black-footed ferrets in the U.S. lives.
As the weather warms this year, wildlife officials are concerned that the plague may move further eastward and they will be unable to stop it. Plague is a deadly and easily transmissible infectious fever spread by fleas.
"We're pretty worried about what might happen this year," said Pete Gober, a biologist with the U.S. Fish and Wildlife Service (FWS) in Pierre, South Dakota.
"If the plague comes back, we could lose a lot of those ferrets."
The weasel-like creatures were once plentiful in the plains, where they fed on prairie dogs. But a federal campaign to exterminate prairie dogs in 1950s and '60s killed nearly all of the ferrets' prey. Deprived of their food source, the ferrets were believed to be gone, too, by 1970.
Then in 1981 a dog in Wyoming killed a ferret and brought it to his owner. Federal officials soon found 18 more and took them for captive breeding.
A decade later small numbers were released in Wyoming, Montana, Colorado, and South Dakota in 11 spots where prairie dogs had survived the earlier eradication efforts.
Now to maintain the ferrets' recovery, officials will have to stay ahead of the plague.
East of the Plague Line
It is no coincidence that ferrets have thrived in Conata, near Badlands National Park (see photo), where 245 of the masked mammals became the only self-sustaining group in the wild.
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