Last week, a federal judge ordered the U.S. Fish and Wildlife Service to reconsider its 2014 decision against listing the wolverine as an endangered species under the Endangered Species Act.

Wolverines are particularly vulnerable to the effects of climate change due to their dependance on snow for reproduction and denning. On April 4, 2016, Dana Christensen, U.S. district judge, ruled that it is time to take action to protect the wolverine.

“No greater level of certainty is needed to see the writing on the wall for this snow-dependent species squarely in the path of climate change,” Christensen wrote, in the ruling.

The debate on protecting the reclusive wolverine has been going on for about 20 years, according to the New York Times. The ruling revived the debate and outlined that the effects of climate change will impact wolverines.

Wolverines have a slow reproductive cycle in addition to relying on deep spring snow for denning. Aja Woodrow, wildlife biologist for the U.S. Forest Service, said because of these and other factors, “they could be wiped out pretty quickly.”

Wolverines mature at the age of three (out of an eight-year lifespan) and reproduce about every other year, Woodrow said. Female wolverines have about three or four chances to produce offspring in their life time, and without deep snow, the chances of the kits surviving are lowered.

Additionally, wolverines are highly territorial to a fault — they cover wide-ranges and are solitary animals. A significant part of their mortality rate is related to fights between wolverines over territory.

“It is the undersigned’s view,” Christensen wrote, “that if there is one thing required of the service under the [Endangered Species Act], it is to take action at the earliest possible, defensible point in time to protect against the loss of biodiversity within our reach as a nation. For the wolverine, that time is now.”

Wolverines in Washington

Wolverines have been on the uprise in the Washington Cascades for the past 20 years, according to Robert Long, wildlife biologist for the Woodland Park Zoo. Spreading from British Columbia, they have been returning slowly to the northern Cascades and moving further south.

Wolverines are returning due to multiple factors, Long said, but they’re difficult to pinpoint.

“As with anything having to do with biology, natural history and the environment, it’s complex and there are a lot of factors that probably interact,” Long said.

Once Washington natives, wolverines died out here in the early 1900s. They were considered vermin, Long said, and fell victim to trapping, poisoning and hunting. Wolverines then returned with large enough numbers in the ‘90s to warrant Forest Service studies.

Now, wolverines have been seen as far south as I-90, and it estimated there are between 25 and 50 individuals in Washington. According to Long, it is difficult to tell because they cover wide ranges of over 100 miles.

This is part of the reason wolverines are moving south, according to Woodrow. When young males reach maturity they’re kicked out of the territory and search for their own range. This will sometimes push the young males south.

Now that wolverines are returning to Washington and other states, the Forest Service is researching how they respond to humans and winter recreation. According to Woodrow, the results so far say that wolverines increase the amount of time they spend move by 20 percent when humans are around.

“They are back now,” he said, “and we’re really excited to see them reoccupy the south Cascades.”