It's the dead of winter. Dall sheep and moose are dying of starvation, disease, avalanches, and accidental falls. Their frozen carcasses are stacking up in the refrigerated wilderness we call Alaska. It's a good time to be a wolverine.
Wolverines are the stuff of legend. Little is known about them. What passes for knowledge is often mythical, or at least highly exaggerated. Poised near the apex of Alaska's wild food chain, there are not many wolverines. There never were. Because they are seldom seen, because of their legendary cunning and ferocity, because they are scavengers, wolverines prompt a wide range of attitudes, from admiration to loathing. Because they are also trapped and hunted, wolverines pose a challenge for wildlife managers.
The Alaska Department of Fish and Game is conducting a research project in Chugach State Park and adjacent areas. Collecting detailed, accurate information on movement patterns and population densities will help maintain wolverines throughout the state.
Mugshot of a scavenger
Phrenologists believe the size and shape of the brain, based on external measurements of the skull, helps explain an individual's behavior. Phrenology is a pseudoscience, but skulls do indeed offer insight about the work an animal is designed to do.
A wolverine's skull is like a curriculum vitae, a concise account of its career and work experience. Like most animals, teeth are the specialized tools of its trade. A wolverine's large molars are ideal for cracking large bones, which may contain the only sustenance left on a well-picked carcass. A prominent sagittal crest, the sharp, bony ridge on top of the skull, anchors large muscles that enhance the crushing strength of the wolverine's lower jaw.
Although capable of killing reindeer and sheep, as well as smaller animals, wolverines are highly adept at scavenging. Like an undertaker, a scavenger's survival depends on the mortality of others. And there's competition. Other predators, like wolves, also eat things they find dead in the woods. But, more than any other mammal, wolverines specialize in finding and consuming the carcasses of large animals. Scavengers are often denigrated by humans (who used to be members of the club), but scavenging is a worthy occupation and scavengers are often interesting characters in the animal kingdom.
Normally weighing as much as a medium-sized dog, about 20 to 40 pounds, wolverines are the largest terrestrial member of the weasel family. They could just as easily, albeit incorrectly, be described as the smallest bear, were it not for their bushy tails. Like bears, wolverines have a phenomenal sense of smell, handy for finding carcasses buried under snow. Wolverines are well-adapted to hunting all winter, with oversized paws to support their weight on the snow, dense under-fur, and glossy guard hairs that shed frost.
Ravens are one of their primary competitors for large carcasses in boreal and arctic regions. Lacking the advantage of wings, wolverines use an indefatigable, mountain-eating lope to inspect their home ranges.
Stocky and muscular, self-assured, adept at breaking into cabins and caches, not to be trifled with, the wolverine invites hyperbole from enthusiasts and detractors alike.
Voracious one-eyed bloodsuckers
Wolverines have a remarkable reputation for cunning, ferocity and gluttony. Early tales and accounts emphasize all three characteristics. Since at least the 16th century, the descriptions of naturalists, moralists, and writers have buried the wolverine beneath a growing mound of fantastical lore.
Buffon, a well-known 19th century zoologist, claimed wolverines, which he called the glutton, preyed on reindeer by climbing a tree and tossing down a type of moss to which the deer were partial. When a reindeer paused under the tree to investigate the bait, the glutton would drop on its back, gripping so strongly that it couldn't be shaken. It would dig into the reindeer's flesh and suck blood until the animal collapsed.
Some early anecdotes belittle the exaggerated claims of previous accounts, but repeat them anyway. Describing its legendary voracity, the editor of The Animal World: It's Romances and Realities was bemused by reports of a single wolverine eating two reindeer in one meal and subsequently squeezing its grossly distended stomach between two trees to make room for more. These, he concluded, were fables. But he seemed to believe a wolverine could kill six or eight reindeer in one night to suck their blood.
Similarly, Erich Pontoppidan, in The Natural History of Norway, scoffed at the "wild notion" of those who believed wolverines were the third cub of a bear, then repeated a tale told him by a friend, a "man of probity," who claimed to have seen a wolverine, chained to a stone wall, "eat himself into the wall."
One of the earliest chroniclers believed wolverines retained their extraordinary powers after death and dismemberment. Olaus Magnus, in his "History of the Northern Peoples," published in 1555, wrote "when men sleep under (wolverine) skins, they have dreams that agree with the nature of that creature and have an insatiable appetite."
Even naturalists who should have known better seemed to have been swept up by the tidal wave of hyperbole and misinformation. In 1758, Linnaeus, founder of the system used to classify all living beings, named the North American wolverine Ursus luscus, which means "bear with one eye," basing his classification on a single specimen from Hudson Bay – one which had lost an eye.
In "Animals of the Arctic in Action and Adventure," a book recommended for "boys of all ages," Alfred Power repeated some admittedly exaggerated accounts and folklore, then noted "people had an enormous capacity for believing the ridiculous." We still do, Alfred, we still do.
Counting a rare and elusive animal
Howard Golden, a furbearer biologist with the Alaska Department of Fish and Game, laughed when I asked him about wolverines dropping from trees to suck the blood of reindeer. He hadn't heard that one.
What Golden wants to learn about wolverines is much more mundane: how many are there? Wolverines are relatively rare, and they are elusive; in other words, they aren't easily counted. So if you need to know how many there are, you have to resort to an estimate, which may be based on a partial count or an even more indirect measure such as calls, nests, or tracks.
A biostatistician at Fish and Game, Earl Becker, has pondered this problem and come up with a solution. Wolverines are active in winter; you don't have to count individuals if you can find their tracks. Wolverines are typically found above tree line, leave easily identifiable tracks on the snow, and move around a lot. Becker's solution has been peer-reviewed and published in the scientific literature. To better understand the method, it helps to know a few details.
Basically, biologists select a large area and divide it into a grid of sample units, each unit three kilometers (a little less than two miles) on a side. They randomly choose about 60% of the units. A day or two after a snowfall covers all previous tracks, they fly over each of the sample units searching for fresh wolverine tracks. They follow each set of tracks forward to the wolverine and backward to where the wolverine's tracks appeared after the snow ended. Back in the office, the statistical program factors in the number of wolverines seen, the number of grids each set of tracks was found in, and the likelihood of finding a wolverine in the grid. Trust me, the nuts and bolts of this method make sense only to a biostatistician.
Like any statistical estimate, Becker's method relies on assumptions. Fortunately, with one exception, observers are able to verify whether the assumptions were met during the flight. The single exception is critical, however. Are all wolverines likely to move – leaving a set of fresh tracks – during the period between when the snow ends and the flight begins? If not, your estimate will be low because evidence of every wolverine wasn't equally available.
In previous research, a collared female wolverine moved less than 100 meters during several 12-hour periods, raising the concern that her tracks might have been missed in an aerial survey conducted less than 24 hours after snowfall.
The truth about wolverines
It's easy to discount the legends, but the truth about wolverines is that there's still a lot to learn.
Using his technique, Becker and others surveyed approximately 1,410 square miles of Game Management Unit 14C in the western Chugach Mountains, including most of Chugach State Park, in 2008. They estimated a density of about 1.3 wolverines per 100 square miles. In other words, 16 to 20 wolverines were thought to be present in the area during the survey. A survey conducted a decade earlier had found a similar density. Surprisingly, this is about the same as wolverine densities in more remote parts of Alaska, like the Talkeetna Mountains.
Golden cautions that an aerial survey provides only a snapshot of the wolverine population. In late winter, when the surveys are conducted, the number of wolverines is at its lowest level of the year, so wolverine population estimates are conservative.
It's also likely that estimates using Becker's methodology may be a little low. There is reason to believe that female wolverines move a lot less than males. Do female wolverines nursing kits linger in their dens for days at a time? Could aerial surveys in late winter, the prime months for finding tracks, be missing females? That question prompted Golden to radio-collar several wolverines to get a better idea of daily movement patterns in winter, when the surveys are conducted. With a better idea of a wolverine's daily movements, a small correction factor could be applied to previous and future aerial surveys for a more accurate population estimate.
Golden and his assistants, Mike Harrington and Todd Rinaldi, have captured 12 wolverines in and adjacent to Chugach State Park and in the Chugach National Forest in the Kenai Mountains. Some were darted from a low-flying helicopter, others were captured in baited live-traps, mostly on Joint Base Elmendorf-Richardson (JBER) with the help of the installation's natural resources personnel.
Radio collars using GPS technology can pinpoint an animal's location at preset intervals, allowing researchers to follow their movements with much greater accuracy than they could decades ago. Golden's radio collars are programmed to record locations every 20 minutes. After about three months, which is as long as the collar's GPS battery lasts, a wolverine's daily movements and much of its home range can be mapped. The collars also allow researchers to download data remotely.
Golden plans to study wolverine movements for another year or two before reaching any firm conclusions, but it's interesting and instructive to examine the range of movements he's found so far.
Green, Blue, and Yellow
Wolverines are renowned for their indefatigable energy. In one 24-hour period, on March 28, a male wolverine, known as "Green" for his ear tag, loped from Bird to the Glacier Creek Valley, avoiding Girdwood, up Crow Pass and into the headwaters of Ship Creek, a distance of about 31 miles. You know someone who's gone that far on snowshoes or skis, you say? Try it in deep snow without snowshoes or skies, where every step punches through the crust.
Wolverines can run up and down mountains at a pace that would quickly bring runners participating in Seward's annual Mount Marathon race to their knees. Most of the movements of collared wolverines follow drainages where carcasses and small prey animals are more likely to be found. However, in one 20-minute interval during his 24-hour marathon, while cresting a steep peak, Green averaged a speed of 4.5 mph.
Most of Green's journeys were less aerobic. He'd find something interesting, probably something to gnaw on, and the colored dots on the map, tracing where he had been, would cluster in one spot.
Green's large home range overlaps that of other wolverines, including the much smaller home range of a female, Blue. A week or two after Blue was darted in the heart of Chugach State Park, she gave birth to one or two kits. Her den, three burrows in the snow about 20 yards apart, was not far from where she was darted. A couple of trail cameras set up near the den caught her moving a kit, possibly because of a close call with an uncollared male. Male wolverines may kill unprotected kits. The new den was about two-thirds of a mile down the valley.
Because she was nursing at least one kit, Blue didn't forage as extensively as Green. Some days she didn't move more than 100 yards from the den. But she was no slacker. Some days she moved 10 or more miles searching for food.
Of all the wolverines Golden has collared, another female – Yellow – stands out because of her unusual home range. Considered a "wilderness species," eradicated throughout much of the Lower 48 states, wolverines are not normally tolerant of human activity. But Yellow, who was a yearling when captured in early 2012, spends most of her time in Far North Bicentennial Park and along the western boundary of Chugach State Park between the South Fork of Chester Creek and Glen Alps. This is a winter playground for many Anchorage skiers, hikers and bikers. And Anchorage is a city of 300,000 residents.
An urban wolverine?
In a surprising move, Yellow was recently spotted by a homeowner on frozen Campbell Lake, on the far side of the city, more than five miles from her normal range. Unfortunately, her collar batteries are dead, and she needs to be recaptured to replace the collar. Now the only way to find her is to track her the old-fashioned way, using a hand-held antenna, or rely on sightings. Harrington, the assistant to Golden, has tried stalking her in wooded areas to dart her and replace the collar without success. They'll try again this winter.
The extraordinary thing about Yellow's last known location is that wolverines are rarely seen in Anchorage neighborhoods. She most likely reached Campbell Lake by travelling down Campbell Creek like the occasional, exploratory bear in summer. Where she'll go next is anyone's guess. Here's hoping she doesn't learn how easy it is to find edible garbage in Anchorage and turn into another casualty of the I-thought-it-was-going-to-eat-my-kids school of thought.
The moose population has declined in the Anchorage bowl, particularly since last winter with its record-breaking snowfall. Moose carcasses were probably in short supply this December, which may have instigated Yellow's unusual foray into the city. Nobody has reported seeing her since her romp around Campbell Lake. Hopefully, she's retraced her steps back to the wilderness in Anchorage's backyard.
A more-accurate estimate?
According to Alaska fur-sealing records, at least 3,499 wolverines were harvested (almost exclusively by trappers) statewide between the winters of 2003-04 and 2008-09 -- an average of 583 per year. The average price paid for raw wolverine pelts from Alaska fluctuated between $130 and $269 during that period.
Trappers operating in Game Management Unit 14C, the area where Becker estimated at least 16-20 wolverines, removed 24 wolverines during the same six-year period, an average of four per year. This was an unsustainable rate of harvest, all things considered. Fortunately, the Alaska Board of Game prohibited wolverine trapping in Chugach State Park in 2009, and only one or two wolverines have been killed in GMU 14C each year since then.
Golden's research will ultimately lead to a more accurate estimate of wolverines wherever the technique is applied. Until then, experienced wildlife managers will manage the rare scavengers conservatively, avoiding harvest levels that might lead to local extinctions.
Rick Sinnott is a former Alaska Department of Fish and Game wildlife biologist. The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch. Contact him at firstname.lastname@example.org