WSU’s grizzly bears lose weight on Thanksgiving?

By Linda Weiford, WSU News

Lynne-NelsonPULLMAN, Wash. – If you think Thanksgiving dinner can pack on the pounds, consider the grizzly bears at Washington State University that eat the equivalent of three such feasts daily during the weeks leading to hibernation. After nearly doubling their weight, they take a winter-long nap – only to wake up trim and perfectly healthy in early spring.

How do they do it?

As the 11 grizzlies living at WSU’s Bear Research, Education and Conservation Center embark on their five-month winter snooze, they’ll continue to reveal answers to the scientists who study them.

The gorging they do before hibernating is a piece of cake, so to speak. Despite the excessive poundage, grizzlies don’t develop diabetes, clogged arteries or heart ailments commonly associated with obesity, said WSU veterinary cardiologist Lynne Nelson, who studies the bruins during their annual slumbers.

Kio-400That’s because, through evolution, grizzly bears have figured out a way to become “healthily obese” before hibernation, she said. While sleeping winter away, they live off massive amounts of stored fat.

In these live-cam shots of grizzlies hibernating at WSU’s bear center, a 9-year-old female named Kio slumbers in her artificial den, top, while two males snuggle next door. As the bears snooze until spring, they’ll shed a lot of weight.

“The hibernation process of grizzlies is a remarkable physiological feat. For five months they subsist in a closed system where oxygen is all they need to survive,” said Nelson who, in artificial dens layered with straw, draws the bears’ blood, takes fat tissue samples and listens to their hearts – carefully. Unlike many hibernating animals that go into a deep sleep, grizzlies can easily awaken when disturbed.

And there’s more. Not only do the bears not eat, but beyond stretches, twitches and shifting their sleep positions, they move very little. Even so, they lose no muscle or bone mass, just excess fat.

“They’re in good shape when they emerge,” typically in late March, said Nelson, who’s been researching the half-ton and heavier creatures at WSU for 12 years.

She and her colleagues study the bears with an eye toward better understanding their nutritional needs in the wild and also aiding human health. Knowledge gleaned could one day be used to combat heart disease, obesity and other ailments, she said.

Several grizzlies at the facility were once “problem bears” in the wild slated to be destroyed, while others were born in captivity.

What’s on their menu for Thanksgiving?

“I think they’ll just nap and hold out for something tasty in the spring,” said Nelson.


Lynne Nelson, WSU College of Veterinary Medicine, 509-335-0789,
Linda Weiford, WSU News, 509-335-7209,