The Wolverine Mystery Being Investigated by Four States
Wolverines look something like a mixture of a dog, a skunk and a bear, with short legs, long hair and elongated snouts. Wolverines also have a distinctive mask of dark fur around their eyes and forehead, and a stripe of blond or ivory fur that runs from each shoulder to the base of the animal’s tail.
Though wolverines are the biggest of the weasel family, according to the Integrated Taxonomic Information System (ITIS), they are still very small. They are normally 26 to 34 inches from head to rump. Their tail adds another 7 to 10 inches to their length. They weigh 24 to 40 lbs.
What Wolverines Eat
Wolverines are omnivores; they eat both meat and vegetation. Typical meals for a wolverine include large game like caribou, moose and mountain goats; smaller animals like ground squirrels and rodents; and even birds’ eggs and berries. They like meat best, though, and will go to great lengths to get it. They can travel 15 miles in a 24-hour period in search of food and will even eat dead animals they did not kill.
Wolverines have a keen sense of smell; they can smell prey 20 feet under the snow. They will dig down into burrows and kill hibernating animals. Wolverines are sneaky when finding food, too. They have strong jaws and teeth, and can crush a carcass and munch right through the bone. They have been known to eat the bones and teeth of their prey. Wolverines also seem to be aware of how to store food. Research shows that wolverines use snow as refrigerators to keep their food fresh. During times when food is scarce, the wolverines will go back to their stockpile to and retrieve a meal.
Habitat and Habits of the Wolverine
Wolverines prefer colder areas because they use the snow for dens, besides food storage. They live in the Arctic and subarctic, in grasslands, Alpine forests, taiga, boreal forests and tundra of Europe, Asia, and in North America in the northern latitudes.
Wolverines are solitary creatures, and need great swaths of territory to roam. Males mark their territory with their scent and only share their turf with females. Their territories can range from 40 miles to more than 372 miles. These hunters are nocturnal, which means they sleep during the day and hunt at night.
Wolverine Mating and Offspring
Wolverines are polygamous. This means that a male will mate with several females. They mate from May to August. After mating, females create dens in which to have their young. These dens are often caves dug in the snow and can be up to 15 feet deep. Females give birth to two or three young at the same time every year, which is usually in the late winter or early spring. Most young are born between February and mid-March. Baby wolverines are called kits. Kits are born with their eyes closed and are covered in white fur. While the females handle the bulk of the rearing, males will visit from time to time and care for the young. Sometimes, kits will stay with their mother until they are ready to have kits of their own. Wolverines are ready to reproduce at around 2 years old. Usually, though, kits head out on their own by September, according to The Wolverine Foundation. Wolverines typically live seven to 12 years.
Are Wolverines Endangered?
The International Union for Conservation of Nature’s Red List lists them as “Least Concern” for extinction, although their numbers are decreasing, especially in Europe, where it is considered “Vulnerable.” Their population is estimated to be between 15,000 and 30,000 individuals. The biggest threat to wolverines is climate change. Warmer weather could mean less snow, which wolverines are dependent on for food and reproduction, as mentioned earlier.
Other Facts About Wolverines
When a wolverine takes a step its paw spreads to almost twice its original size as it presses against the ground. This makes it easier for wolverines to walk on snow. It’s like built-in snowshoes.
Wolverines are also called skunk bear, quick-hatch, glutton and stink-bear.
A Scientific Exploration of Wolverines
Western States Wolverine Conservation Project
The four states, Montana, Idaho, Wyoming, and Washington, along with federal, tribal, and university partners, recently finished their first report on what’s called the Western States Wolverine Conservation Project. The document details the unprecedented multistate survey of this largest land-dwelling member of the weasel family. “This whole effort started with putting people who know wolverines in a room and asking the question, ‘What can we do to make sure this species is here decades from now?’” says Bob Inman, Montana Fish, Wildlife & Parks Carnivore-Furbearer Program coordinator.
Researchers traditionally study wolverines anecdotally or with small-scale projects in known hotbeds in a few mountain ranges and national parks. The new survey looked for the mountain carnivores in an area of nearly 55,000 square miles. Researchers and wildlife managers now have baseline information to determine whether distribution of this iconic high-country species grows or shrinks in the future. The new data will also help them identify and conserve core breeding populations and decide where to protect connections between critical habitats.
Where are the Wolverines?
Scientists have long known that wolverines are one of North America’s hardiest creatures. But they didn’t know exactly where the animals lived, or how habitat fragmentation and declining snowpack from climate change affect the species. Unlike elk and other game species that generate hunting license dollars used for monitoring and management, wolverines create no income for research. The resulting lack of information, especially regarding the possible effects of reduced snow pack, led the U.S. Fish & Wildlife Service in 2013 to consider listing wolverines under the Endangered Species Act.
Though the agency eventually concluded that listing was “not warranted,” the four states decided to marshal forces and come up with a collective strategy to conserve wolverine populations in much the same way as if the species had been federally protected.
The Process of Gathering Statistics on Wolverines
Researchers started by identifying the best wolverine habitat in the four states that either held or could hold wolverines. (In recent years, wolverines have also shown up in California and Colorado, but those states don’t have breeding populations and weren’t included in the survey.) Then biologists divided that vast mountainous landscape into 633 cells, each measuring 87 square miles. Using traditional bait stations aimed at capturing wolverine hair, scientists randomly sampled 183 of the cells to see which ones held wolverines.
The states partnered with the U.S. Forest Service; U.S. Fish & Wildlife Service; National Park Service; the Northern Arapaho, Eastern Shoshone, and Confederated Salish and Kootenai Tribes; University of Montana; and Montana State University. The partners raised nearly $1 million for the labor-intensive work.
Survey crews hiked, skied, snowshoed, and snowmobiled deep into mountain ranges in the 183 grid cells and placed bait or scent stations with cameras along with genetics-gathering hair traps. They hung deer, beaver, or other meat on trees into which wire brushes were inserted to catch the hair of wolverines climbing to the bait. Trail cams installed nearby captured images of animals that investigated the sites. The cameras and brushes were checked once a month over four months at stations that could be accessed; stations in extremely remote sites were not visited until the following spring. Snagged hairs were sent to the U.S. Forest Service’s National Genomics Center for Wildlife and Fish Conservation in Missoula for analysis to determine if they came from a wolverine or another carnivore such as a marten or fisher.
The survey detected wolverines in 59 of the 183 cells that were sampled. But just because a camera or brush didn’t detect a wolverine didn’t mean the animals weren’t living in that cell. To account for what’s known as “imperfect detect-ability,” the study hired Paul Lukacs of the Quantitative Wildlife Ecology Lab at the University of Montana. Lukacs analyzed forest cover and other characteristics of cells with high and low levels of detection (ranging from one detection per month over four months to only one detection over four months). That allowed him to estimate the probability that cells where wolverines weren’t identified did contain the animals. He estimated that if a wolverine lived in a sampled cell, there was a 92 percent chance of detecting it there at least once over the entire four-month survey. “That’s a really high detection probability for a rare animal,” Lukacs says. “It shows that the biologists knew how to attract wolverines to the bait stations.” After accounting for imperfect detectability, the team adjusted the estimate of occupancy at cells where wolverines were not detected and concluded that wolverines were likely present in roughly half the 633 cells.
Discoveries Not Anticipated about Wolverines
One of the most exciting discoveries was in Wyoming, the southern reach of known wolverine populations in the Northern Rockies. The mountains surrounding Yellowstone National Park have long been known as core habitat. But the survey detected wolverines for the first time in the Gros Ventre Mountains and the southern reaches of the Wind River Range, up to 100 miles south of the park. In the southern Wind River Range, they also identified a male and a female at the same camera station, suggesting that wolverines could be breeding in the area. “It was pretty exciting to find them that far south,” says Zack Walker, Nongame Wildlife Program supervisor for the Wyoming Game and Fish Department.
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