Wintry Wonders of the Wolverine
Wolverines are secretive creatures that are seldom seen. A glimpse of one disappearing over a ridge or behind a boulder is a once in a lifetime sight. Not only are they secretive and seldom seen, but they are still few and far between. Wolverines inhabit vast ranges creating many challenges for viewing these elusive creatures. They are a uniquely adapted animal that can survive the long harsh winters in our alpine environments of Idaho.
Wolverines have been called by many names, skunk bear, carcajou, or glutton being a few of them. Wolverine was a name used for other predators, like lynx and bobcats by early Euro-american settlers who knew little of the wildlife. While wolverines may have a bear-like appearance with their stocky form, they are the largest member of the mustelid or weasel family. A wolverine isn’t much bigger than a medium-sized dog but they are built to endure harsh environments. Their five-toed paws with long claws work like crampons and help them gain traction on snow and ice. Their stocky body and short rounded ears help them conserve heat, while their thick fur has a hydrophobic coating. This hydrophobic coating repels water and frost, keeping them warm and dry! Wolverines were, and still are, hunted for their fur because of its frost resistant qualities.
A wolverine’s scientific name, Gulo gulo, literally means glutton as they will often gorge themselves on food when caught or found. Wolverines have a reputation for being fierce and aggressive hunters and they live up to it. However, they will often scavenge for carrion and in the summer will also eat some plants and berries. Fruits and veggies aside, meat makes up the majority of their diet.
Wolverines can take down animals much greater than their size, like elk or moose, but only when that animal is compromised in some way. Often large sick, starving, or stuck animals will become a wolverine’s dinner. Mainly wolverines hunt smaller prey such as rabbits, squirrels, or other rodents. When prey is in short supply in the long winter months wolverines will use their impressive sense of smell to search for dead and buried animals in the snow. Their long claws are not only good for moving across the mountains and valleys but also for catching prey or digging for dinner. If a big kill is made or found wolverines may not consume the entire thing. What is left over is cached for a later meal. With prey being scares in the winter a wolverine must have a large range to find food.
Carcasses found or stored in the mountains in the winter will be frozen solid. For many animals, this would prove to be another obstacle of winter. However, wolverines, like other members of the weasel family, have a molar that is rotated 90 degrees inward to aid in the ripping and tearing of fresh or frozen meat.
The rarity of a wolverine sighting owes in part to the fact that they have a huge home range. A male’s range can be more than 240 square miles (620 sq km) and usually will encompass several females’ ranges. A female’s range tends to be smaller, of 50-100 square miles. Compare this to a black bear’s range of 10 to 60 square miles or a mountain lion’s range of 50-100 square miles and you get a picture of how much space wolverines need. Mountains and ridges with valleys filled with snow don’t pose as an obstacle to wolverines.
In the U.S. wolverines were once found from Washington down to the Sierra Nevada’s in California, through the Rockies in Colorado to Montana and all the way east into Minnesota. Today, due to hunting, trapping, habitat loss, and habitat fragmentation they are only found in isolated regions of the lower 48. In the Rocky Mountains in the early 1900s wolverine populations experienced significant declines or in some cases localized extirpation. Since then numbers have increased some, with wolverines returning to areas where they were once extirpated. Globally, wolverines live in the circumpolar region, through northern Europe and Asia as well. However, their numbers are still on the decline globally. Habitat loss is one of the reasons for the wolverine populations’ decline. Climate change also affects wolverines as they need snow!
Wolverines are creatures of harsh and cold environments. They rely on snowpack to make travel easier than over rocky terrain. They also, perhaps most importantly, rely on snow for their dens. A female wolverine needs snow over 1 meter deep to dig her den. Tunnels and den areas can be 5 to 6 meters deep under the snow! Often dens will be made in ravines or areas where snow accumulates or in the timberline under logs or in avalanche fall where trees and logs will provide extra structure to the den. Wolverine dens often have long tunnels in hardened snowdrifts. Sometimes the dens will even lead down to the talus or rocks and boulders that can provide additional protection. In harsh winter environments dens protected by snowpack help insulate the mother and kits from the frigid temperatures above.
These dens aren’t just a simple tunnel and cave; they often have multiple chambers with tunnels connecting them. This means that a shallow snowbank will not suffice for wolverines and they need a large amount of deep snow. Wolverines also have two different dens they use, a natal den where the kits are born, and a maternal den where the mother will move the kits to when they are older. The female will then have kits born usually in February to mid-March. They will stay in the natal den for about 9-10 weeks when they can follow the mother around and are weaned. They may use more than just the two dens depending on disturbance and snowmelt.
This means that deep snowpack need to last until at least May. With rising temperatures, snowpacks are decreasing or disappearing. A wolverine’s habitat must, therefore, include many large snowfields that last well into the summer. Winter recreation, like snowmobiling also have major impacts on wolverines, often causing mothers to move dens due to the added activity and noise.
Various organizations have proposed that listing the wolverine as threatened on the Endangered Species Act which would provide it with more protections. However, wolverines have yet to be listed. It is estimated that fewer than 300 wolverines are left in the contiguous United States. Wolverines are not only facing habitat loss, and disturbance from winter activities, but also loss of genetic diversity and genetic exchange. Idaho has great habitat for wolverines with its Wildernesses and wild areas, vast mountain ranges, and regions with an incredibly cold climate. However, this habitat needs to be protected for years to come. Enjoy the Sawtooth’s beautiful views and snowy mountains, and think of how many unique animals, like the wolverine, can make this place their home.
Hannah Fake, Lead Naturalist