After six months of bed rest
s Blood clots
s Heart failure
s Oxidative and energetic stress
s Blood vessel dysfunction
90% reduction in muscle mass
Severe disuse osteoporosis
Carbohydrate, protein and fat
Bed sores No bed sores
Physiological feats Hibernators are somehow able to survive six months of stillness,
even though a similar lack of movement would threaten human health. Studying the changes
that hibernators go through may one day make their skills transferable. SOURCE: O. FRÖBERT
brown bears undergo each winter, includ-
ing how they have such high cholesterol
but no increased risk for heart disease.
“ We see the brown bear as a living library
of information,” Fröbert says. “It’s an
animal that has solved a multitude of
problems that humans face.”
Insights gleaned from bears and
ground squirrels may also help research-
ers prevent or reverse bone and muscle
loss in space travelers, elderly people
and children with muscular dystrophy.
Such lessons could reveal ways to ren-
der people confined to bed rest immune
to blood clots, bed sores and muscle
and bone atrophy. Therapies designed
to mimic ground squirrel hibernation
strategies could save soldiers and acci-
dent victims from bleeding to death. And
these critters just might hold secrets for
reducing damage from strokes or heart
attacks, and even for preserving organs
for transplant after they are cut off from
a blood supply and put on ice.
Extra pounds, no problem
Nearly everything about the way an
animal’s body works changes when it
hibernates, and preparations start weeks
or months in advance. The first order of
business is to fatten up.
“Fat is where it’s at for a hibernator,”
says Matthew Andrews, a molecular
biologist at the University of Minnesota
Duluth who studies 13-lined ground
squirrels. “You bring your own lunch
with you.” Packing lunch is necessary
because the animals go on the world’s
strictest diet during the winter, surviving
entirely off their white fat. “They have
their last supper in October; they don’t
eat again until March,” Andrews says.
Bigger fat stores mean a greater chance
of surviving until spring. “If they go in
really chunky, nice and roly-poly, that’s
going to be a good hibernator,” he says.
Bears also watch their waistlines
arteries that can’t be collected from live
bears come from bears killed by hunters
during the legal hunting season.
COURTESY OF O. FRÖBERT
Researchers race to gather fat samples
from a tranquilized hibernating brown
bear after tracking it down in a forest
in Sweden. The bear has to be back in
its den within 60 minutes, when the
sedative wears off.
expand in the months before settling
in for the season. The brown bears
Fröbert studies pack on the pounds by
chowing down on up to 40 kilograms
of blueberries a day. Such gluttony
among humans could have severe consequences: Obesity is associated with a
greater risk of heart disease and diabetes, among other ailments.
To see how fattening up affects Scandinavian brown bears, Fröbert and his colleagues ventured into the wilds of Sweden
following signals given off by radio transmitters or GPS devices on tagged bears.
Bears can be dangerous close-up. Even
hibernating bears can rouse to action
quickly, so scientists tracking down
bears in the winter use darts to tranquilize the animals from a distance. Scientists studying the bears in the summer
tranquilize them from a helicopter.
Once a bear is under the tranquilizer’s
influence (which takes about five minutes), the scientists have 60 minutes
max to get the animal from its den, weigh
and measure it, draw blood samples and
do minor surgeries to collect fat and
other tissues. The bear is returned to its
den by minute 61.
Precious materials collected during this high-pressure encounter need
to be analyzed within 24 hours, so the
researchers often test for levels of cholesterol or certain proteins in the blood
while working in the snow or at a nearby
research station. A pilot sometimes
flies samples from field sites to a lab in
Denmark in order to meet the deadline,
Fröbert says. Samples such as bones and
The bears’ cholesterol-defying arteries
are just one of the evolutionary tricks
allowing hibernators to spend six
months as furry couch potatoes without
negative side effects.
Such inactivity wreaks havoc on the
human body, which can’t maintain strong
muscles and skeletons without weight-
February 25, 2012 | SCIENCE NEWS | 27