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Female bears give birth while in hibernation.
Female grizzly bears normally become sexually mature in their fifth year. Mating normally occurs between late May and early July. Females will normally mate with as many males as they can over the 3-4 weeks of the breeding season. Females will not come into estrus and mate when they are nursing or raising cubs, about 3-4 years.
Through a process referred to as delayed implantation, the fertilized ovum divides a few times and then floats free within the uterus for about six months with its development arrested. Gestation begins at the start of denning. Sometime around the denning period the embryo will attach itself to the uterine wall and after a period of eight weeks (January or February) the cubs will be born while the mother is still in hibernation.
Delayed implantation clearly serves an important survival need for the mother. Should she not have enough fat reserves to carry her through the winter, the embryo will not implant and it is simply reabsorbed by her body.
The number of cubs born normally ranges from one to four with 2.4 cubs being average. Climate, DNA and food supply are important in determining of the size of the litter. Recent research points to the sow's ability to give birth to cubs from different boars, which would indicate that females produce eggs at different times throughout the breeding period.
At birth the cubs are blind, toothless, hairless and very small. They weigh 21 to 25 ounces. About the size of a chipmunk. As soon as they are born they will nurse on their mother who remains asleep. This is the only time in a bears life when it will eat while in hibernation.
About the size of a chipmunk!!!
WOW - didn't know that!
more @
http://www.yellowstone-bearman.com/bears.htmland imagine how many hoomans would LOVE to be able to sleep through childbirth
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