Reproduction and Cubs
George Narita, researcher for Grzimeck’s Animal Life Encyclopedia, states that the only time the male lives together with the female is between April and June. However, the female’s fertile ova are not implanted until the following fall when the mother prepares to go into the den and is literally snowed in. This process is known as delayed implantation. Pregnant females dig a den, usually in a snow drift on the coast, facing away from the wind, from October to December. The cubs are born between the months of December and January, and they remain there until as late as April. Polar bears give birth to one to three bubs every 28 months.
Care of Young
For at least 20 months after birth, polar bear cubs drink their mother’s milk and depend on her for survival. Their mother’s success at hunting seals directly influences their own well-being. The mother ceases to feed throughout winter, living off her stored fat. While most female polar bears make very good mothers, malnourished or inexperienced sows have been known to kill one or all her cubs. In some cases, if more than two cubs are born, the runt of the litter is weak due to forfeiting many meals to the stronger siblings.
Females with cubs generally avoid adult male bears, which sometimes attack the young and eat them. Highly protective mother bears are capable of driving off much larger males. According to Narita, even young polar bears have amazing endurance and can follow the mother for considerable distances, often marching behind her in a line. They run at her side only in areas of very deep snow where the mother is sinking in. Running at her side prevents them from stumbling in her footprints. The mother does not go into the water with her young until winter is past, and even then, only when necessary. She also avoids land and proximity to land, since there is more danger for the young on land than on the ice flow. The following winter, she returns with her young to the den. After the second winter period is over, the young generally stay with their mother, although in an emergency they could strike out on their own. Females in the Low Artic wean their cubs as they approach their second birthday, while in the High Artic, where the conditions are more demanding, care for their cubs an additional year. It is also at this time when the cub is now a capable hunter.
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|Page last updated March 17, 2005|