Research Briefs

The wolverine’s melting world

A wolverine walking across the snow, its coat glinting in the sun.

The largest land-dwelling species of the weasel family, the wolverine resembles a small bear. Today, it lives primarily in the northern boreal forests and subarctic and alpine tundra of Alaska, Canada, the northern United States, Scandinavia, and Russia. It once ranged into central Europe and the midwestern United States; Michigan is even nicknamed the “Wolverine State.” Wolverines have experienced a steady decline in population since the 19th century due to trapping, range reduction, and habitat fragmentation. (Image ©iStockphoto.com.)

The wolverine is known for its strength and ferocity, but these qualities cannot protect it from a warming world. NCAR research suggests that this aggressive predator may struggle to survive in the contiguous United States over the coming century.

The wolverine’s U.S. habitat, which includes parts of Washington, Idaho, Montana, and Wyoming, correlates with regions of persistent spring snow cover. Females den in the snowpack from early February through mid-May, making late spring snow cover critical to reproductive success. With its large feet and dense fur, the animal is highly adapted to extreme cold and snow, and can’t tolerate summertime highs above about 72°F (22°C).

NCAR scientist Synte Peacock used recent simulations from the Community Climate System Model to explore possible future changes to spring snow cover and summer air temperatures in present-day wolverine habitat in the contiguous United States. She analyzed model output from three different carbon emissions scenarios: an optimistic, though less probable, scenario in which emissions stay level until 2020 and then decline sharply to zero by 2075; a less optimistic scenario in which emissions stay near present-day levels until 2050 and then decline sharply at the end of the century; and a worst-case scenario that assumes no dramatic action is taken to reduce emissions.

The results show that, under climate conditions falling between the latter two scenarios, spring snow cover is likely to nearly or completely vanish by the middle of the 21st century in present-day wolverine habitat. In addition, maximum daily temperatures in August are likely to increase dramatically under the last scenario, with most days of that month above 90°F (32°C) by the end of the century. If dramatic emissions cuts were made within the next decade, as according to the first scenario, projected changes in snow cover and temperature would be much more modest, according to the study.

Two attempts to list the wolverine in the contiguous United States under the Endangered Species Act have failed. On April 15, the U.S. Fish and Wildlife Service announced that it was again initiating a status review to determine whether the species warrants protection under the ESA.