In November 2023, it made the news: Wolverines received protection as a threatened species under the Endangered Species Act. The North American wolverine was being listed as a distinct population segment in the contiguous U.S.
What does that mean? Why? Experts believe that there are fewer than 400 of the animals left in the lower 48. The exact reason stated by the United States Fish and Wildlife Service for the listing was: “Current and increasing impacts of climate change and associated habitat degradation and fragmentation are imperiling the species.” In short, habitat connectivity between protected blocks of high-elevation public lands and potential lack of long snowy winters are the concern. Wolverines need room to roam, and they like cold, high terrain.
I am not going to debate the merits of listing or legal proceedings, as there are lots of bright academics, agency wildlife staff, and attorneys wrestling with that issue. Rather, let’s take a look back in time and see where this all started.
First Things First: Early Wolverine Distribution and Status Research
First things first: Wolverines are cool. At one time in the northern Rockies, they were the wildest weasel that nobody realized was still prowling around. So what happened? How did they end up in their current plight?
It wasn’t that long ago that it was common practice for poison-laced bait to be placed on public lands to kill predators and protect livestock — domestic sheep, in particular. And poison, especially spread on large protein baits, like a deer or cattle carcass, can kill many species indiscriminately. Hawks, eagles, and vultures have incredible vision and can spot carrion from great heights. Bears, wolves, and wolverines have fantastic sniffers and can smell protein from great distances. In fact, wolverines can smell food buried under deep snow or far upwind in a mountain canyon. So, it’s not surprising that this distribution of poisoned baits on vast areas of public land took quite the toll on a host of species 50 to 100 years ago, especially wolverines. These practices are of course not legal now, but, at the time, poisoning and unregulated trapping were the reason that wolverines were thought to be almost extinct in most of the U.S.
Wolverine in Glacier Park – Mr. and Mrs. John Fabian – Montana Wildlife 1956
Given the public perception that wolverines might be extinct, it was big news when, in 1956, a winter caretaker in Glacier Park snapped a rare photo (above) of a living wild wolverine. It was so newsworthy, in fact, that the photo made the inside cover of Montana’s fledgling wildlife magazine (the same publication that would eventually become Montana Outdoors), where it was labeled “Le Carcajou” (the French translation of wolverine). The oversized weasels of legend were still here.
The sighting caught the eye of Montana’s long time furbearer biologist at the time, Fletcher Newby. He started assembling verified observation records for these almost mythical animals, many of which came from trappers, who saw wolverine tracks in snow as they traversed remote mountain haunts during the winter — or, on occasion caught one. Trapping was still legal and more widely accepted then.
By 1964, Fletcher Newby had collected enough observations from trappers, fur buyers, and naturalists to publish a distribution and status review. His information suggested that wolverines had likely been near extinction in most of Montana since 1920.; from 1920 until about 1940, the animal was almost unknown and unseen in Montana, and likely in Idaho, Wyoming, and even Washington as well. Then, beginning about 1940, wolverines were seen and shot or trapped with increasing frequency in northwestern Montana. Many of these newly reported wolverines were males, which is quite typical when carnivores begin to expand their range and recolonize former habitats. The population trend appeared to be slowly improving — as much as an extremely low-density species on the landscape could. As Montana’s first furbearer expert, Fletcher knew that wolverines were special, and his reporting provided important information about the elusive animal. Interestingly and fittingly, the Bitter Root Land Trust now gives out an annual “Fletcher Newby Award” to some of their conservation partners.
Research Advances as Biologists Meet Wolverines on Their Own Turf
Fast forward to 1971, and the work of another pioneering biologist would provide new insight into wolverines. Fresh off his success in Idaho capturing, radio-collaring, and studying the secretive mountain lion, University of Idaho scientist Dr. Maurice Hornocker and his new co-investigator, Howard Hash, from the then Montana Fish and Game Department, took on the impossible. They set out to capture and track wolverines in the greater Bob Marshall Wilderness area adjacent to Glacier National Park. The vast, wild landscape is hard to navigate during the long, cold winter, but, beyond Glacier, it was the place where wolverines were at the time, so the two biologists set out to meet the wolverines on their own turf.
From 1972 to 1977, Maurice, Howard, graduate student Pete Ramirez, and the Koehler brothers captured, marked, tracked, and studied the elusive wilderness wolverines throughout the South Fork of the Flathead River. They caught and released a total of 24 wolverines, consisting of nine adult males, eight adult females, and seven subadults. This was a monumental achievement, given nobody had ever attempted to do this before. But that is what Maurice liked to do: pioneer new research techniques on challenging and sometimes dangerous species. Eventually he would move to the Russian far east to initiate the first study of Siberian Tigers. But for now, wolverines were his research nemesis and greatest challenge.
Maurice had a secret research weapon to combat the remote country in his research partner, Howard. Howard was a skilled bush pilot and a wildlife biologist. He could fly supplies into the remote Spotted Bear airstrip to resupply food and gear, and, as the statewide furbearer biologist for Montana Fish and Game, he was also on call to fly in and help sedate captured animals. During the study, Howard flew about two flights per week and logged about 460 hours tracking the wide-ranging wolverines in rugged mountain country. Remember this was before satellite GPS collars, so you literally had to find the animals from the air or track them on the ground. The team discovered that these big weasels on steroids usually moved about six miles between flights, and one exploring wolverine moved an incredible 16 mountain miles in three days. Wolverines truly are wandering weasels.
Howard Hash, left, and Dr. Maurice Hornocker, right, holding a sedated wolverine. Pete Ramirez photo.
The research team estimated a minimum population size of 20 animals for the 1,300 sq km area, or about one wolverine per 65 sq km. At the time, before the enormous surge of human population growth we’ve seen in the Rockies and the widespread concerns over changing precipitation patterns and temperatures, the wolverine research team believed that the study area population was stable. The animals were living deep in a big, snowy, wild mountain wilderness area, after all.
By using bush planes, backcountry skis, snow shoes, or plain old boot leather, the team was also able to track the wolverines to discover that the animals used quite large landscapes to meet their annual needs. The size and shape of their home ranges were not affected in the least by rivers, reservoirs, highways, or major mountain ranges. Wolverines would go anywhere at any time. After the field work and data analysis was completed, the researchers determined that the average yearly range of male and female wolverines was 422 and 388 square kilometers, respectively. That’s a lot of ground for a big weasel.
Wolverines also showed fidelity to a given area, but several individuals of both sexes made frequent long forays into other drainages in the Swan and Flathead mountain ranges. However, all wolverines in the study ultimately returned to their original home ranges. The home ranges overlapped between individuals of both the same and opposite sexes. The team suggested that territorial defense was nonexistent. Wolverines did, however, scent mark to maintain spacing temporally, but not spatially. Lastly, wolverines appeared to select higher elevation spruce fir cover types throughout the year, but this preference was greatest in summer. Afterall, it’s cooler up high in this habitat at the higher reaches of the forest canopy. Wolverines seem to look for ice age like conditions.
At the study’s end, Dr. Hornocker and his team postulated that, in Montana specifically, protected wilderness habitats and ample public lands, coupled with more restrictive state trapping regulations should provide for secure wolverine populations in the foreseeable future. This notion would hold until new technologies and new research efforts showed up in the 1990s.
New Research Technology Leads to New Insights
Satellite tracking collars and new DNA investigative techniques emerged on to the wildlife scene in the 1990s. Aided by this new technology, Idaho Fish and Game biologist Jeff Copeland led new wolverine research in the rugged Sawtooth Range of Idaho, where he discovered the important relationships between deep snow and wolverine dens. Copeland then joined forces with Dr. John Waller in Glacier National Park to study the wolverine (scientific name Gulo gulo), producing research that would be featured in biologist and author Doug Chadwick’s book, The Wolverine Way.
It was in this same period, in the High Divide, Robert Inman led new wolverine research in and around Grand Teton National Park, and his work expanded into other areas in Montana. He documented, among other things, long distance dispersal movements, linkage habitats, and home range replacements after study area mortalities. Kevin McKelvey, Michael Scwhartz, Len Ruggiero, and John Squires began Forest Service wolverine research efforts using cutting edge genetic analysis tools. And, Kim Heinemeyer explored the impacts of winter recreation and indirect habitat loss on wolverines in Idaho.
The author holding a tranquilized male wolverine on Jeff Copeland and John Waller’s Glacier National Park wolverine research project.
Justin Gude, research chief for Montana Fish, Wildlife and Parks, and a field team of his state agency biologists, Tribal Wildlife partners, National Park Service teams, and others created a multi-state wolverine census using hair grabbing traps for genetic analysis. This enormous geographic census revealed that wolverines were either already roaming several western states and not previously detected, or they have expanded their range in recent decades. Wolverines are now being studied with the best science has to throw at them.
Wolverines will climb trees to reach baits at hair snagging sites that are used for DNA identification. Photo by Chris Hammond FWP
Interestingly, the ice age rooftop of the lower 48 states is found in Colorado. It’s more than a mile high. In fact, in many areas, the Colorado high country is more than two miles high. Based on habitat modeling conducted by several leading wolverine wildlife scientists, there is probably more suitable high, wild snowy wolverine habitat found in Colorado than any other state in the lower 48. Population reintroduction or augmentation is definitely an option on the table in that terrain.
More recently, in a 2014 peer-reviewed paper, USDA Forest Service, Rocky Mountain Research Station research ecologist Kevin McKelvey and his team of genetic experts described the need to consider both genetic diversity and appropriate behavioral repertoires for future reintroduction efforts in the lower 48 states. They go on to say that the optimal source location for wolverine translocations to California or Colorado may be the Canadian Rocky Mountains just north of the border, where genetic diversity is relatively high and environmental conditions are similar to those in the western mountains of the United States. Hopefully a mountain wolverine in hockey country is the same as a mountain wolverine in cowboy country. Having been involved in challenging grizzly bear augmentation logistics and outcomes in my past career, I think moving a few wolverines to the mile high state is definitely worth a try.
Wolverines, more than most species, need landscape connectivity between unbroken higher habitats to continue to reclaim their former ranges and to keep things connected. I for one hope these long clawed furry climbing machines continue to prowl the higher rugged reaches of all of our remaining wild country.
Jim Williams is a Certified Professional Wildlife Biologist by the Wildlife Society and Partnerships Manager at Heart of the Rockies Initiative. He joined the Initiative in 2022 after a long career as a biologist for Montana Fish, Wildlife and Parks. Other notable achievements and talents of his include writing and publishing a book, The Path of the Puma, alligator wrestling, surfing, and being able to make friends with anyone. The latter is important for his work as well, where people and connections motivate him. Jim loves storytelling and mentoring younger professionals, and he is excited to work with rural and local communities to conserve wild things and wild places
