http://channel.nationalgeographic.com/episode/expedition-grizzly-3909/factssnip...
True hibernators are animals whose body temperature drops to a few degrees above freezing, and when disturbed, can take over an hour to wake up. A grizzly’s hibernation is more closely related to a long rest, and the bear can wake up quickly if disturbed. During hibernation the grizzly’s body temperature, normally 98.5 to 99 degrees, drops about 10 degrees to about 89 or 90 degrees.
# A grizzly has a four-chambered heart, just like a human. Its heartbeat is normally 40 to 70 beats per minute, but during hibernation, its heartbeat slows to 10 to 18 beats per minute.
# Grizzlies hibernate, or sleep, about six months a year. Females hibernate longer than males, especially if they have given birth to cubs.
# Grizzlies generally dig their own dens for hibernation and make beds out of dry vegetation. Burrows are often located on mountain slopes where deep snow may serve as insulation until spring. Grizzlies often dig under large stones or in the roots of mature trees. Bears may return to the same den areas year after year.
# Grizzlies become sexually mature between four and six years of age. Mating of brown bears occurs from May to July and females may copulate with several males during estrus, which lasts 10 to 30 days. Fertilized eggs develop to the blastocyst stage, but do not implant until November, when the female has begun hibernating. A six to eight week gestation follows, and births occur from January to March, usually while the female is still in hibernation. Total gestation time ranges from 180 to 266 days.
snip.....
Read more:
http://channel.nationalgeographic.com/episode/expedition-grizzly-3909/facts#ixzz19MrHUZIf