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Are red foxes in Beartooth Mountains ice age descendants?

Are red foxes in Beartooth Mountains ice age descendants?

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BEARTOOTH LAKE — The last ice ages don’t seem so distant on this February morning.

Snow is driven sideways in a steady, stinging wind. Visibility is limited by an engulfing white cloud. And the icy cold easily stabs through several layers of clothing.

Welcome to Patrick Cross’ office in northwestern Wyoming’s Shoshone National Forest, just north of Yellowstone National Park.

It is a place where this winter blizzard seems appropriate, given that Cross is studying whether red foxes in the Beartooths are related to migrant foxes from Asia during one of the last two glacial epochs hundreds of thousands of years ago.

Dating back to the 1800s, observers had seen the foxes inhabiting the high Beartooth Mountains. The foxes were noticeably different with their lighter coats, nearly white faces and gray undercoats. Fur trappers observed they had furrier or larger feet, better for travel atop the snow. The differences earned them the nickname of glacier fox.

It’s a study that has brought Cross, a 29-year-old former Billings resident, back to the mountain range he explored in his youth. His work for the Bozeman-based Yellowstone Ecological Research Center will also form the basis for his University of Montana master’s thesis in systems ecology.

“This summer I’ll get the genetic data back, along with the collar and snow tracking data,” he said. “I’ll be spending next summer and fall wrapping up the analysis and then completing and defending my thesis at the end of next fall.”

Ice dogs

There are 10 recognized red fox (Vulpes vulpes) subspecies in North America. Researchers believe that a large western population of genetically isolated red foxes were the forefathers of four now distinct subspecies: the Sierra Nevada red fox, V.v. necator; the Sacramento Valley fox, V.v. patwin; the Cascade Range fox, V.v. cascadensis; and the Rocky Mountain fox, V.v. macroura.

“Red foxes first arrived in North America two ice ages ago, during the Illinoian glaciation, by crossing the Bering Strait,” Cross explained as he took shelter in a small grove of lodgepole pine trees just downhill from the snow-covered and closed Beartooth Highway, the site of a new fox trap he was building. “They were pushed south at the front of advancing glaciers.

“As the glaciers receded, the foxes pushed north or went up in elevation, tracking that boreal ecosystem they had grown up in,” he added. “Those populations became isolated in the Sierras, Cascades and Beartooths.”

The Illinoian glaciation is a period roughly defined as 310,000 to 128,000 years ago. That frosty time in North America was followed by the Wisconsin glaciation, the most recent ice age that extended from 35,000 to 11,500 years ago. As the ice sheets advanced and retreated across North America during late Wisconsin time, it’s believed that another pulse of red foxes trekked into North America. Foxes of this second wave are more closely related to those living in Eurasia, Alaska and northern Canada.

“So the question is: which one is the Beartooth fox?” Cross said. “It could be an offshoot of the older (group) adapted to living at these elevations. The problem with that theory is that 10,000 years ago, the Beartooths were still covered with ice.”

Cold study

Looking for answers, Cross has spent the last two winters trapping, collaring and collecting tissue samples from red foxes in the Beartooth Mountains along Highway 212, roughly between the closed highway's parking area and Island Lake. He also is picking up scat, fur and tracking the cat-sized canids that top out at about 12 pounds.

He and his assistants have managed to capture and collar nine red foxes in the study area that ranges in elevation from about 7,000 to 10,000 feet. At this time of year, it is an inhospitable environment. The temperature regularly dips below zero, snow is piled 10 feet deep and only specially adapted animals can scrape out a meager existence.

It’s well documented that red foxes are a highly adaptable animal, covering more areas on Earth than any other terrestrial carnivore, including parts of North America, Europe, Asia and northern Africa. They are omnivorous, eating everything from seeds to small mammals and scavenging the kills of larger predators – a form of feeding called kleptoparasitism.

So far, Cross has documented some unusual happenings. One yearling fox was killed – probably by wolves – while scavenging on a bull elk carcass.

He also witnessed one male red fox spend most of a day catching voles in a field and then burying each one it caught along the highway near the Top of the World Store. At the end of his hunt, he walked back along the highway and picked up the 12 voles, likely to provision a high-elevation den.

One collared fox was recorded traveling 50 square miles last March, an unusual feat since most foxes in nearby Yellowstone National Park have home ranges of about 2.5 to 5 square miles.

Foxes are famous in folklore for being smart and secretive, doing most of their hunting at night. Yet little is known about the rugged foxes that seem to have adapted for living at high elevations, a topic of only a handful of scientific studies.

Food for thought

One of those studies, in 1998, found that red foxes in Yellowstone National Park kept to forested areas, avoiding sagebrush meadows frequented by coyotes and wolves. One theory about the Beartooth foxes is that they were pushed to the high mountains by competition with larger canids like coyotes and wolves, which will kill the foxes.

“Generally, these canines are living above that inter-canine competition area,” Cross said, although they will drop down to lower elevations to scavenge wolf kills of elk and mule deer.

The foxes are also doing a bit of their own killing, mainly of voles living under the snow, but also finding snowshoe hares, grouse and – a surprise to Cross – raiding squirrels’ whitebark pine nut middens to dine on the protein-rich food.

“Even though it was not expected, it wasn’t particularly surprising given the high nutritional value of whitebark pine nuts,” he said. The nuts are also a favorite food of grizzly bears in the fall.

Fox fecal samples screened by Cross have so far shown the Beartooth animals dining on 16 different foods, including grouse whortleberry and shrews.

“This is really cool stuff,” he said. “It’s exciting because it illuminates part of the natural history of what this animal is doing. It’s also illustrating that whitebark pine nuts might be even more important than we already guessed.”

Log trap

Trapping the Beartooth foxes in winter is important because it allows Cross the opportunity to use the foxes’ food stress to his advantage. Using small, square live traps made out of logs, the foxes are trapped inside when they pull on the bait that is hooked to a trip wire. Remote camera photos have shown skittish foxes running in and out of the boxes at first, wary of being trapped.

“We can load this thing up with elk quarters,” Cross said as he demonstrated how the traps work. “We can overload the fox’s sense of security because there’s more meat in the trap than it will get all winter.”

The traps are typically placed near the edges of a fox’s range, rather than in the middle of its habitat. The traps are checked every morning at about 9, the first activity of the day. Trapping will continue into mid to late May, depending on the snow conditions.

Cross also spends time on skis following fox tracks in the snow, a noninvasive means of learning about the foxes’ travel routes, habitat use, where they scent mark, the snow conditions as well as providing insight into what they are eating and killing.

“That’s something the GPS collars don’t tell us,” Cross said.


Cross will receive DNA information from the tissue samples he has taken later this year. Previous samples have already shown that the Beartooth red foxes are not as closely related to foxes in nearby Yellowstone National Park as the Yellowstone foxes are related to red foxes in eastern North Dakota, hundreds of miles away.

He noted that some people have questioned his motives for studying the animals, concerned that if the foxes are found to be the descendants of Illinoian ice age foxes, that environmentalists may use the information to declare the animals a threatened species worthy of protection and leading to government regulations like those protecting grizzly bears.

Cross said that’s not his intention. He simply wants to learn more about the Beartooth Mountain red foxes.

“Last year I caught a fox at Clay Butte, and five days later I saw a fox looking through the window at me in Cooke City with its GPS collar on,” Cross said, making him wonder who is tracking whom. “I think the fox has more advanced technology.”


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