have included bears in two sections: hibernation
and torpor. This was the first
time that we ever did research and found out that different books
might have different information that doesn't agree about the same
Most books say that bears are not
"true" hibernators. This is because they:
||Have times through
the winter when they wake up and walk around.
||Don't have a big
lowering of body temperature.
Bears live in forests, swamps, and mountains.
They live in the Arctic, North America, South America, Europe, and
Asia. Wild bears [not in zoos] live about 15-30
years. They live longer in zoos. Bears do sleep a lot of the winter but their
body temperatures don't drop very much. This is how the female
can take care of her cubs that are born during winter. True
hibernators take a long time to wake up from their winter sleep but
bears are alert and know what is going on around them. They
can get up right away.
Bears are omnivores
which means they eat plants and animals. They try to stay away
from people. They will attack any person or animal who
threatens them, their cubs, or their dens.
have cubs, bears usually live alone and don't travel around in
groups. Black bears will eat all kinds of things, from dead
animals to grass, roots, and berries.
In the fall, bears start to look for a winter
den. This den will be safe and somewhere that the bear doesn't
go at other times of the year. Bears like to make their dens
in caves, hollow trees, banks of creeks or even big pipes.
Brown bears always dig holes for dens. Sometimes they even dig
tunnels to the den.
When they make their den, they drag in leaves and
tree branches for a bed. The den will be big enough for the
bear to move around and stretch but small enough that the bear's
body heat warms it. When it begins to snow, they crawl inside
to sleep. The snow will lay over the den and help to hold the
bear's body heat inside.
Males mate with the females and then leave them to find
shelter. Bears can be pregnant
for three to eight and a half months. Different kinds of bears
will have different lengths of time. The mother bear [sow]
will have between one and four cubs during hibernation. The
sow will have only one litter
a year and this litter can be born anytime between October and
March. The cubs are very small. They weigh from 7-25
ounces each. Some weigh less than a pound of butter.
Cubs are born hairless. They stay with their mother two years
and she teaches them to hunt and take care of themselves.
During hibernation, a bear's eyes will be open when it
is awake but it might be groggy. Its body gets a little cooler
but not as cold as other hibernating animals. Since it mostly
sleeps and lays around, the body fat that it stored in the summer
and fall lasts longer. It doesn't take too much body fuel to
sleep. Its body does lots of things while it is in
hibernation. It makes its own water and recycles wastes.
Bears won't drink or get rid of wastes for a few months. They
will lose about eight pounds a week during hibernation or
torpor. The weight they lose will be from stored fat and not
muscle. This means that when they leave the den in the spring,
they are still strong. In Spring, they will wake up and
leave the den. They will be thinner and very hungry.
Here's something interesting. Bears don't get rid
of wastes--or go to the bathroom--for a few months. The urine
is broken down inside their bodies and reused as protein to help the
bear keep its muscles healthy. A 'plug' of feces, hair, and
nest stuff forms at the end of the bear's digestive tract.
This comes out when the bear leaves the den and goes to the
bathroom. Disgusting, but interesting.
Polar bears can go into hibernation at any time of the
year. They will do it if they can't find food. This
allows them to adapt to
having no food. Most polar bears don't hibernate but some
pregnant females will. They make their dens in the fall, give
birth during the winter, and stay there until spring. The
temperature inside the den can get 40 degrees hotter than the air
outside just because of the bear's body heat.
Bears aren't like birds that migrate, or move
away from bad weather. They won't leave their area to find a
warmer place. They adapt to the climate around them by
sleeping through the cold season. Scientists
disagree on whether bears hibernate, but all think they do go into a
torpor. Torpor is a sleep where the animal is a little
alert but kind of drowsy or sluggish.
Back to Hibernation