© unknownWolverine
The last time wolverines were known to live in Colorado, Theodore Roosevelt had just died and women had not yet won the right to vote. But now, 90 years later, researchers using radio tracking devices have followed a wolverine into the state.

The scientists concede that the return of one animal to a species' ancient range is hardly cause for jubilation. "Somewhat of an anomaly," Rick Kahn, an official in the Colorado Division of Wildlife, called it in a statement.

But the researchers hope their efforts to track the young male, designated M56, will help explain why only an estimated 250 to 500 wolverines remain in the lower 48 states and what their fate might be in the face of development and climate change.

Wolverines live in Alaska and Canada, and "we know they used to be in Idaho, Montana, Wyoming, Utah, Colorado, California and Washington," said Robert M. Inman, who directs the Greater Yellowstone Wolverine Program of the Wildlife Conservation Society, the organization that also runs the Bronx Zoo.

But "it is one of the most elusive and just mysterious creatures," Mr. Inman added. "Few people have seen them."

If any animal could survive in the Rocky Mountain West, one would think it would be the wolverine. The largest land-dwelling member of the weasel family, it is strong, tenacious, sharp-toothed and cunning. Although adult wolverines typically weigh only about 30 pounds, they are stocky and bearlike, and easily prey on far larger animals like sheep.

But wolverines could not survive the trappers who prized their almost waterproof fur, the ranchers who killed them with poison bait and the developers who divided their range with highways and other infrastructure.

The animals have evolved to require huge territory for roaming, and they reproduce slowly. Males might stake out 500 square miles or more, Mr. Inman said, sharing the landscape with two or three females that breed every other year and usually produce a litter of two.

In an effort that began in 2001, Mr. Inman and other researchers have been trapping wolverines, outfitting them with collars bearing radio transmitters and recording their movements. M56 was caught in December near Grand Teton National Park in Wyoming, Mr. Inman said, and researchers tracked him as he wandered from the Togwotee Pass to the Wind River Range and across sagebrush areas of central Wyoming to the Shirley Basin.

"From there, he went across I-80, Friday night of Memorial Day weekend," Mr. Inman said. "Between midnight and 4 a.m., we think."

The researchers believe that M56 crossed into Colorado on June 1, Mr. Inman said. But he would not say where. "We don't need to have people chasing him around," he said.

Mr. Inman and other researchers plan to use data on what landscapes the wolverines favor to predict what impact global warming will have on them in the years ahead. So far, there are more questions than answers.

But the travels of M56 demonstrate that wolverine conservation "has to be a multistate effort at the big landscape level," Mr. Inman said.

"That's the way this species operates, and that's the way we have to think," he added.