A decadelong study on Teton Range wolverines helped provide the groundwork for U.S. Fish and Wildlife’s proposal to grant the mustelid Endangered Species Act protection.

For years, biologists and conservationists fighting to establish federal protection for wolverines were stymied by a lack of basic knowledge about the elusive member of the weasel family. Information on home range size, movements, social structure, population density and dispersal tendencies was absent or minimal, said Bob Inman, a carnivore biologist with the Wildlife Conservation Society.

The paucity of data was particularly acute in the Lower 48, inhabited by just 250 to 300 wolverines. A study Inman headed that focused on animals in the Teton and Madison ranges of Wyoming and Montana filled in many of those blanks.

“People had done studies in Alaska and the far north,” Inman said, “but, we really didn’t know whether wolverines were doing something differently down here.”

On Friday, the U.S. Fish and Wildlife Service recommended listing wolverines as “threatened.” There’s a 90-day comment period before the agency will make a decision.

Climate change a danger
The proposal cites the species’ low population density and climate change’s potential impacts to its high-elevation habitat as threats. Scientists have found that by 2085,  warming and reduced snowpack will cut suitable wolverine habitat in the Lower 48 by nearly two-thirds.

“We certainly learned through the study that this is a species that seems to occupy cold, unproductive habitat,” Inman said. “They eke out a living at higher elevations, where there’s not a lot of food and deep snow conditions for most of the year.”

Researchers participating in the study captured and collared 30 wolverines between January 2001 and February 2008. They found just four adults — two females and two males — regularly inhabiting the Tetons.

“The population is probably between four and seven individuals, depending on whether there’s young that year,” Inman said.

The biologists also learned about the extreme distances over which wolverines disperse and how they move around their massive home ranges. Home ranges for females studied averaged 117 square miles, and males averaged 308 square miles, the study said.

Inman told a story about a young male wolverine collared near Jackson in 2002.

“We put a GPS collar on him and released him there in the Tetons, and he just disappeared,” he said. “Eventually, he came back to the Tetons and dropped his collar, and we found it. He went down to Pocatello, Idaho, and back to the Tetons in three weeks. It really opened our eyes to how these animals can travel unbelievable distances in a short amount of time.” 

Later in its life, the same male wandered into the Wind and Salt river ranges, Inman said. In 2009, another male Inman’s team collared near Togwotee Pass ventured all the way to Colorado. The species hadn’t been documented in that state in almost a century, he said.

Wolverines were extirpated from Wyoming and most of the contiguous United States by the 1930s.

Species reoccupying range
Despite some individuals’ prolific travels, the tenacious 17- to 40-pound mustelid is just now reoccupying much of its former range. The southern edge of the reoccupation of the Rockies is unknown but likely in the realm of Jackson Hole, Inman said.

“If all of the Greater Yellowstone Area was occupied, we might have maybe 100 wolverines,” he said. “But, that’s not enough to be a viable population.”

A separate Fish and Wildlife proposal announced Friday allows Colorado’s wildlife agency to transplant an experimental population of wolverines. Colorado has enough high-mountain terrain to support up to 100 animals, the proposal said.

Although modeling suggests that prime habitat exists, wolverine occupation of the Wind River, Gros Ventre, Wyoming, Salt, Bighorn and Absaroka ranges is unknown, Inman said.

Wyoming officials are not considering similar efforts to speed re-establishment of wolverines in former haunts, said Bob Lanka, the Wyoming Game and Fish Department’s supervisor of biological services.

“We have observations of wolverines in the Big Horns, but not breeding populations,” Lanka said. “We have not had any specific conversations about possibly reintroducing them, but that may be something that we consider in the future.”

Game and Fish is reviewing the federal proposal and will submit formal comments, Lanka said. Wolverines’ potential “threatened” status would likely not have much impact on hunting regulations, oil and gas development or recreational access, he said.

“This species is extremely low density,” he said. “Because of their extreme habitat ... these are places where we’re not doing a whole lot of exploration for oil and gas.”