RUSSELL SPRINGS -- The black-footed ferrets still are healthy, and a growing number of prairie dogs are starting to emerge from their burrows.

That might signal an end to what is thought to be something of a forced hibernation, brought on by the unusually dry conditions that settled in on the region in the last half of 2010.

But there's plenty about the prairie dogs' disappearance that's still not known or, for that matter, understood.

What is known, with as much certainty as wildlife biologists can ascertain, is the disappearance is not the result of sylvatic plague.

"It definitely doesn't look like plague here any more," said Dean Biggins, a wildlife research biologist for the U.S. Geological Survey in Fort Collins, Colo. Biggins, who played a key role in the rescue of the last surviving 18 black-footed ferrets, accompanied fellow wildlife biologist Travis Livieri to Logan County to review the mystery of the disappearing prairie dogs.

"It's the most plausible explanation," Livieri said of hibernation.

It was Biggins who first suggested in late January that the prairie dogs simply might have gone underground, into forced hibernation brought on by unusually dry conditions.

Prairie dogs get all their moisture from the plants they eat, and the plants dried down and quit growing when the moisture shut off in early August.

After 0.87 of an inch fell on Aug. 6, about 4 miles southwest of Winona -- perhaps the closest weather station to where the black-footed ferrets were reintroduced south of Russell Springs -- the rain machine all but shut off.

Only 1.18 inches of rain fell at that weather station the remainder of the year, split between 14 occurrences.

Conditions were even more dismal 71βΡ2 miles south of Page City, where only 0.6 of an inch fell in the same period. But even 12 miles southwest of Oakley, conditions were only slightly better, with 1.43 inches recorded.

Those dry conditions, Biggins said might have caused the prairie dogs to "go down and flatline their temperature," he said.

It's likely the prairie dogs rouse themselves from the forced hibernation and head above ground to check out the conditions, perhaps clear away waste that has accumulated.

As temperatures moderate and grass greens up, Biggins suspects the prairie dogs will start emerging from hibernation en masse.

But there's a catch, he said.

"If this is stressful enough to put them into hibernation, it's been a pretty tough time and maybe some of the weaker ones won't ever come out," he said. "That's what happens with the more typical hibernating ground squirrels."

That's just a guess, however. There's been little research on the issue of forced hibernation, other than one case in Colorado, which Biggins coincidentally supervised.

How many prairie dogs might not survive is uncertain.

"You'd expect maybe the young born last year," he said of those particularly vulnerable, "since they lost half of their good growth period. The end of the summer wasn't any good, and they may be the ones to suffer the most by having to hibernate."

To test that, as best they can, Livieri and Biggins tried to make rudimentary counts at several locations on the Haverfield-Barnhardt complex south of Russell Springs where ferrets have been reintroduced.

They also surveyed the ferrets as well, finding 11 in the short time theysurveyed the area.

"We certainly saw prairie dogs," he said.