People who drove through Snoqualmie Pass in early January came back talking about the grass still poking up through the meager snowpack on downhill ski runs. Skiers are on the well-covered slopes at Snoqualmie now, but climate change — if that's what we're seeing — doesn't bode well for folks who make a living from low-elevation ski areas. Nor does it bode well for animal species that make a living in deep snow around here.
The risk goes well beyond this region, of course. The plight of polar bears faced with less Arctic sea ice on which to hunt seals has been well publicized. (A recent report suggests that the big bears are developing a taste for snow goose eggs.)
But here, in the upper corner of the country, the looming change may soon give us a new federally listed species: the wolverine, Gulo gulo, the world's largest terrestrial weasel. Many of the Northwest's most charismatic species rely on chilly water or deep snow. Salmon, which rely on cool spawning streams, may be driven from much of their current habitat. In the Columbia Basin, the only spawning streams with cool enough water may eventually be those that lie in the mountains of Idaho — a location that means fish are forced to run the gauntlet of the lower Snake River dams.
The Canada lynx, which lives in the North Cascades and the Selkirks, is adapted to living in snow. Its big feet keep it from sinking in. It dines primarily on the snowshoe hare, whose big feet keep it from sinking in, too. Take away reliable winter snow, and the snowshoe hare population disappears. And so does the lynx's evolutionary advantage. Other species' genetic equipment becomes more beneficial: The bobcat, which is less adapted to snow but is a larger, more competent generalist, starts displacing the lynx.
And then there's the wolverine. The return of wolverines to Washington and the discovery two years ago that they're breeding here has been big news. Scientists know there are at least 18 of them in Washington, mostly in the North Cascades, although they've started appearing south of Highway 2 and a single male has been seen around Mount Adams.
For unknown reasons, male wolverines sometimes take off on long solo journeys. One currently lives in the southern Sierra Nevada and another in the southern Rockies, far from any established population. Because females evidently don't have the same wanderlust, these males aren't likely to start new populations.
Once upon a time wolverines lived all across the northern tier of states and way down into the Rockies and Sierra Nevada. They were exterminated before 1950, partly through deliberate trapping, but probably mostly as collateral damage when people set out to poison coyotes and wolves. (Not that people were above poisoning wolverines directly. "Some trappers intentionally poisoned them to prevent the destruction of more valuable furbearers," Keith Aubrey of the U.S. Forest Service's Pacific Northwest Research Station in Olympia and colleagues wrote in 2007. They noted that intentional poisonings even occurred in Yellowstone National Park in the late 1800s.)
Then, 20 or 30 years ago, new wolverines started walking south across the Canadian border. Most came down from Alberta into the northern Rockies, where they've established breeding populations. A smaller number has come down from British Columbia's Coast Range into the North Cascades.
The animals have no physical adaptations as obvious as the big feet of the lynx or snowshoe hair, but wolverines, too, are adapted to snow. I have an old top-of-the-line Eddie Bauer parka, heavy with down filling and topped with a wolverine fur ruff. Why wolverine? Because it's the only fur that, exposed to damp human breath in super-cold temperatures, won't ice up.
Behaviorally, they are largely confined in places where the snow gets deep and lasts well into spring. They make dens and raise their young in deep snow caves. "Virtually all reported wolverine reproductive dens (sites where kits are born and raised prior to weaning) are relatively long, complex snow tunnels that may or may not be associated with large structures, such as fallen trees or boulders," the Aubrey paper explained. J.P. Copeland and colleagues surveyed wolverine populations around the northern hemisphere and found virtually all of them in areas where deep snow lasted until at least May 15.
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