Single mother
The female cares for her cubs by herself. They follow her for a year or two and hibernate together during the first winters. Thereafter the cubs search for a partner and a territory for themselves. Sons often wander hundreds of kilometres while daughters settle close to their mother's turf. The wanderings are perilous, and many cubs will die before they settle.
Infanticide !
As long as the female walks with cubs she will not be in season. If she meets a male bear in rut, she rejects him. The male can then kill her cubs, in order for the female to quickly come into heat so the bears can mate.
Hard to be a mother
The most common cause of death during the cubs' first four years, is being killed by a male bear. To have all her cubs killed, is heavy for the female.
Shrewd tactics
One way a female can protect her cubs is the following : A male bear mates with several females and remembers them. When he meets a female with cubs that he has mated before, the cubs could be his. Therefore, he doesn't kill them. By mating with several males, a female causes more males to hesitate to kill her cubs.
