Grizzly Bears Are Waking Up Early This Year, and Climate Change Could Make That a Bad Habit
What could wake a hibernating bear? An abnormally warm winter, apparently.
Yellowstone National Park’s 150 grizzly bears are on the move, according to the National Park Service, which confirmed the first bear sighting of the year on Feb. 9—almost a month earlier than usual. That could be due to climate change.
The past decade has been the hottest on record for Yellowstone, about 1.4 degrees above the region’s 20th century average.
Al Nash of the National Park Service said the sighting meant the agency had to push up its annual announcement to warn park goers the grizzlies are out.
“In mid-February, grizzlies aren’t usually on the minds of the cross-country skiers and snowshoers in the park, so hopefully we can get the word out to be on the lookout,” Nash said.
There are an estimated 550 grizzlies in the 28,000-square-mile greater Yellowstone area, and reports of bear sightings outside the park boundaries are coming in from Montana and Wyoming as well.
Typically, the NPS grizzly bear broadcast comes in mid-March, but after an early cold spell in November and December, Yellowstone’s 2015 winter has been averaging temperatures about 10 degrees Fahrenheit warmer than usual.
“We’re getting 40-degree days in February, where we often see 20 below zero,” Nash said.
That’s messed up the threatened species’ internal clocks—they’ve adapted their behavior to avoid the months that coincide with food shortages, cold temperatures, and snow on the ground. When they do wake up, it’s typically to a smorgasbord of animal carcasses—deer, bison, and elk that succumbed to the harsh winter weather.
But there hasn’t been a harsh winter in the area. Does that mean there won’t be as many dead treats for bears? Park staff actually do surveys to see how many carcasses are around at the end of each winter and designate areas—carcass hotspots, if you will—as off-limits to humans to limit bear and human interaction.
This year’s carcass surveys aren’t complete, so it’s still too early to know what the warmer winter means for the bears’ high-protein food source. But the implications of what rising temperatures could mean for grizzly bears isn’t lost on Nash.
“They’re omnivores, so they’re eating whatever’s available,” he said. “But it is certainly possible that a milder winter could have an impact on the number of animals that succumb to the winter cold, and it certainly could have an impact on that food source availability as the grizzlies wake up.”
Climate change has already impacted the region’s white bark pines, with the warmer temperatures allowing bark beetles to attack large swaths of forest at higher elevation levels than they could usually live in. The white bark pine nuts are an essential part of the grizzly bear’s diet. On top of that, cold-water-loving fish such as cutthroat trout—a grizzly bear favorite—are at risk of losing habitat in lower elevations as streams heat up.
A report from the conservation organization Greater Yellowstone Coalition warned what mild winters could mean for bears and other scavengers.
“Following milder winters—likely to become more common—fewer grizzly bear cubs survive, at least in part because fewer carcasses, especially those of elk, are available as food than following traditionally harsh winters,” the report stated, adding that black bears, gray wolves, foxes, coyotes, and bald and golden eagles—all scavengers—could be affected.
“The long-term trends of climate change’s effect on animals like the grizzly bear are what we’re concerned about,” said Greater Yellowstone Coalition wildlife director Chris Colligan. “We need to make sure the bears continue to have food sources that reduce conflict with humans—keeping bears out of our trash, and bear-proofing nearby communities is vital.”