bears sleep through winter to conserve food, especially during winter when food is short, tapping energy reserves, body fat, at a slow rate.
you can find out more at here: http://en.wikipedia.org/wiki/Hibernation
Koalas don't hibernate through Winter.
Scientists have done many experiments and the result is that mostly all bears hibernate/sleep the whole winter. There are very few types of bears that do not hibernate the whole winter. The sloth bear, though, does sleep all winter.
repair and restoration theory
sleep all day long.
Under trees, in deadfalls, in shady spots that willows provide, etc.
American black bears spend much of the winter dormant, but scientists do not consider them true hibernators, because they frequently awaken from deep sleep to leave their winter dens for short periods. Their dens may be caves; hollow, standing or fallen trees; or burrows.
They hibernate in the winter when it is the coldest and food is scarce. Contrary to popular belief, not all bears go to sleep in the beginning of winter and emerge in the spring. Most bears will come out a few times during the winter but go back in to continue to hibernate.
Yes, the female Polar Bear or "sow" does dig. She will dig to build a den, in big deep snow drifts. The den is usually about the size of a telephone booth, with several small alcoves, where the female may give birth to cubs, if she is pregnant, during the long winter sleep. Females are not the only Polar Bears to take a "winter sleep" or to dig a den. When the temperatures drop and stay constantly low, indicating winter has arrived, all Polar Bears, will make a den, to take a long "winter sleep" in, not to hibernate in. Inside the den, it is about 40 degrees on average, warmer than outside. They are insulated and protected from the extreme temperatures and weather outside. For more details see sites listed below.
No not all polar bear cubs survive the harsh long winter.
no
they dont, there is not a single of species of bear that have ever been known to hibernate. bears torper during winter, this is when they sleep, but can still wake up and walk around, hibernation is when an animal is in a deep sleep for the whole winter and cannot and will not wake up at all. torper is just like a lazy sunday morning when you wake up at 6:00, then fall asleep, then wake up and walk around again, then fall asleep. its the same concept
a batter butt In the non-winter months, honeybees don't sleep at all.