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  Sleeping Bears Help Heart Study    

Sunday, December 28, 2003

Hannelore Sudermann - Staff writer

Everyone needs extra sleep in the winter. But two slumbering bear cubs at Washington State University are doing much more than getting their cold-season rest this year. They're contributing to a ground-breaking study in heart function.

  Bear Heart Study  

Veterinary cardiologist Lynne Nelson has been bonding with the pair of grizzlies, named Mica and Luna, since their birth at WSU's Bear Research, Conservation and Education facility last January.

Just before their eyes opened in February, Nelson took over for their mothers and bottle-raised them for eight weeks in her office. She was pressed to respond to their hungry cries about every two hours. From there, the curious cubs were moved back down to the bear research center, where they spent the summer frolicking in the enclosures at the east end of campus.

They had daily contact with humans, mostly with Nelson. They snacked on their favorite treats, which include olives, hard boiled eggs, mandarin oranges and, of course, honey. They sometimes practiced simple tasks, such as holding still to have their blood pressure taken.

"Working with them is such fun," Nelson said. "One of their favorite activities this summer was to somersault four to five times in a row down the small hills in the enclosure. They would get to the bottom, run back up to the top and do it again, head over heals."

The days of bear care were to adapt them to people so the pair could take part in a multi-year study. Thanks to their human time, the cubs are friendly, docile and willing to cooperate for brief, non-invasive examinations such as blood-pressure tests, ultrasounds and being weighed.

Nelson's plan is to observe their hibernating hearts, which function at about 20 percent of their awake heart rate. A hibernating bear's heart looks a lot like the heart of a human with heart disease, Nelson said. What interests her is how the bear's heart survives the prolonged reduced rate of hibernation and then quickly recovers to normal activity in the spring.

According to the American Heart Association, cardiovascular disease is the leading cause of death in the United States. While one in five people has some form of cardiovascular disease, it doesn't just affect adults. Each year about 40,000 babies are born with heart disease. The statistics for animals are similar. Nelson is hoping that what she learns will contribute to research benefitting animal and human health.

Nelson isn't the first to study hibernating bears, but in other cases the ursine subjects are often sedated. The WSU veterinarian wanted to work with animals in their normal hibernating state. "Drugs do affect a lot of things, including heart rate," she said.

So hand-raising them has made the bears comfortable with humans and equipment. In fact Mica reacts to Nelson with affection and makes low rumbling sounds while trying to get close to her.

"People have said bears aren't social creatures, but they are," Nelson said. "And they remember people very well."

Luna's memory is the sharpest. "She catches on so fast," Nelson said. "Any thing I have taught Luna, I have often showed her only one time."

Mica and Luna have been hibernating since Oct. 20. During the more than five months of their sleep, they won't eat or drink. They stay curled together at the back of their den, stirring for only about a half hour each day to stretch and reposition.

"These little cubs have just a huge nest set up," said Charles Robbins, the bear research director at WSU.

Last week, Nelson and Robbins climbed into the small, dimly lit den to visit the cubs and take readings of their hearts.

Decked out in coveralls and boots, they got down on the floor and gently woke the three-foot bundles of fur curled on a bed of sweet-smelling straw. These bears each weigh about 125 pounds, and encouraging them to hold still for the ecocardiogram is no easy feat. Even during their hibernation time, they're curious.

To calm them, Nelson and Robbins cradled the bears on the floor and ran their hands through the dense, 4-inch fur.

Though waking the bears was inevitable, the experts took steps to minimize the disturbance. They didn't wear cologne, they whispered in the den, and they took care not to eat strong-smelling food for lunch.

They've also spent time over the past two weeks just going into the den so that when they brought in the new $35,000 portable echocardiograph device, the bears would not be disturbed by the extra bodies or equipment.

While Luna stuck to her straw bed last week, Mica, the more inquisitive one, was taken with a stack of rags Nelson and vet technician Pam Thompson brought in. She also was curious about the large white echocardiograph machine Gary Radamaker, a technician, had strapped to his chest. But, like a toddler, she quickly forgot it when he stood and turned to the wall and she couldn't see it anymore.

As the bears settled on the floor with the humans, Radamaker kneeled down so Nelson could reach the machine with one hand while pressing an electrode against Mica's chest under her arm with the other.

The screen of the electrocardiograph showed a two-dimensional picture of the bear's heart as well as a Doppler measure of the flow of the heart's valves.

When a human or animal has heart disease, they lose muscle function in their heart, Nelson said later. "But with bears, somehow they're able to preserve that muscle function."

It's by studying the prolonged slowing of the heart rate without increased muscle stress that Nelson hopes to learn more of what might help other animals, as well as humans, recover from heart disease.

Mica and Luna also are contributing to other studies about bear physiology, musculature and bone structure.

As the scientists in the den finished their readings, they brought in another bale of straw and put the cubs to bed.

Luna groggily and tenderly raked the straw beneath her while Mica stayed close to Nelson. Though the bears won't see the humans for at least a week, the scientists will watch their sleep daily over an infrared camera that sends images to computers at work and home.

The next visit with the equipment is scheduled for February, and the bears aren't expected to come out of hibernation until April. At that time, they'll weigh about 90 pounds, nearly 30 percent less than they weighed in the fall.

Mica and Luna aren't the only bears to help with Nelson's research. Two more cubs are due this winter, and Nelson plans to go through the same bottle-feeding, bonding and playing with the new pair.

"It is a privileged feeling to be friends with Mica and Luna," Nelson said. "I don't think there is any animal that is as fun-loving and enjoys life as much as a bear cub."

Hannelore Sudermann can be reached toll-free at (866) 332-3674 or by e-mail at

Revised April 5, 2001     |     Printer Friendly Version

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