Come wintertime, wildlife descends from snowy peaks to milder climate

February 21, 2012

By Tom Corrigan

State wildlife biologist Brian Kertson spent five years studying the local cougar population, including a 130-pound, 2-year-old male tranquilized, captured and tagged in the Cedar River watershed in 2008. Contributed

As the snow moves down the mountains reaching lower elevations, so do most mountain wildlife inhabitants, from small animals to deer and elk.

And just in case you were wondering, bears don’t hibernate.

Those are two basic bits of information passed on by local experts asked to describe what happens to Issaquah wildlife during the winter months. It’s not the temperature, but snow that motivates most animals’ cold weather behavior, said Stephen West, associate director of the School of Environmental and Forestry Sciences at the University of Washington.

For the most part, cougars, deer and other local wildlife can tolerate any cold the Northwest brings their way, West said. It’s mountain snow they can’t deal with — it makes it more difficult for them to get around and much more difficult for them to find food. So as snow appears, many animals head for lower elevations. There are exceptions, including bears.

Bears don’t migrate, but rather stay in their normal territory, said Kenneth Raedeke, an affiliate professor in the UW’s Wildlife Science Program and the president of an environmental consulting firm.

And despite what you may have heard all your life, bears don’t hibernate, Raedeke and West said. Full hibernation means an animal is unconscious and its body temperature drops to match the surrounding temperature, West said. For an animal the size of a bear, waking up from such a state would require more biological energy and heat than they have available to them.

While they don’t fully hibernate, bears do go into a sort of relaxed state for perhaps three or four of the coldest months of the year, Raedeke said, adding a bear’s heart rate can drop as low as eight beats per minute. Even so, bears can and do remain somewhat active, coming out of their hiding spots periodically. And if you happen to stumble into an occupied bear den during the winter, the resident likely will take notice.

“They can be completely awake and moving very quickly,” Raedeke said.

Still, he said that most of the time bears in their winter state won’t bother you if you don’t bother them.

What kind of spots do bears seek out for their sort of semi-hibernation? Raedeke and West both talked about caves, but West said bears will seek anything that will provide them with overhead cover: large hollow tree stumps, rocky areas, and downed trees or logs.

As for cougars and other big cats, generally they will follow their prey down the mountains, according to Raedeke and West. Many deer migrate up and down the mountains, depending on the season. Traditionally, elk did the same, but local elk have become very urbanized and don’t migrate nearly as much they used to do, Raedeke said.

And while it seems logical for big cats such as cougars to move up and down the mountains with their prey, that isn’t so much the case in the Issaquah area, according to Brian Kertson, a biologist with the state Department of Fish and Wildlife.

Kertson is the author of an extensive study of cougars in the Issaquah area. His study included tracking cougars with GPS and radio transmitters. According to Kertson, there were few seasonal changes in the territories of the cats he tracked. Their menus did change with the seasons, with beavers becoming common targets in late winter. Deer and elk are the cats’ favorites food for much of the rest of the year.

“I really don’t have any explanation for it,” Kertson said of the dietary changes.

Regardless, he said winter is a great time to be a cougar.

During the colder months, deer and elk can be especially vulnerable to predators because of their lower nutritional condition and their increased focus on finding food.

“This is especially true if the winter is colder and wetter than normal,” Kertson said.

Further, in colder months, cougars don’t have to worry much about opportunistic bears who ordinarily might try to steal a cat’s fresh kill.

All three experts said there seems to be little truth to the idea that animals, including large cats and bears, will start invading your backyard trashcans during the winter looking for an easy meal. Bears simply aren’t out and about much, according to Raedeke and West.

As for cougars, Kertson’s study showed there are only three or four resident cats on the three mountains near Issaquah, though there always may be transient cats with no set territory, cats that are more or less just passing through. In any case, Kertson said he doesn’t believe cougars come into urban areas any more or less during the winter months.

Raedeke talked about coyotes being plentiful in Western Washington, saying he has even seen them where he lives in Lake Forest Park. The animals don’t exhibit much seasonal movement, he added.

While large mammals get plenty of public attention, smaller animals and birds also inhabit the local mountains, naturally. Recently, Kertson was out and about completing a winter waterfowl count, one he said has been done annually for many years. The count includes ducks, geese and swans. One might assume many birds head south for the winter.

“This is down south for many of them,” Kertson said, adding many species move from further north to relatively warmer local climes.

He said Lake Washington is a great spot to birdwatch in the winter months, though swans may be scarce.

There are many nonmigratory birds in Western Washington, West said. Birds form mixed species flocks in colder months, something that might never happen in the summer.

“It’s all about finding food,” he said, adding the large, mixed flocks also help protect birds from predators.

As for finding food, birds do very well even during the winter months and are probably hardier than many people give them credit for, West said. By the way, those backyard bird feeders filled with seed might not be doing as much good as you think.

“Certainly, if you put them out, the birds will use them,” West said.

But he added that only a certain percentage of local birds eat seed. Others are more interested in insects or spiders and animal debris than seeds. These are the birds you see hopping around, bobbing up and down in bushes and similar spots, West said. And they are very skilled at finding what they need, he added.

As for smaller animals, such as squirrels or raccoons, neither changes their behavior much in winter, according to West. The Douglas squirrels living on the Westside of the Seattle area, as well as the red squirrels more common on the Eastside, are territorial and simply don’t change locales with the seasons. If a squirrel finds a good territory, he or she may stick to the spot for a lifetime, West said.

As for raccoons, they have become an urbanized animal, he said. They will largely stay in the same area, no matter the season. West added, that as with bears, the idea that small animals hibernate in winter is largely a myth, at least in this area. The only local animal that fully hibernates is a jumping mouse. Even other types of mice stay active in winter, going about their business beneath the snow cover, if there is any.

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