Animal Survival: Polar Bears

CARE OF YOUNG

Female polar bears have four mammary glands. Mothers nurse their cubs in a sitting position, or lying down on their side or back.
During their first few weeks of life, polar bear cubs nurse most of the time and stay close to their mother to keep warm.
For the next three or four months the cubs nurse as often as six times a day. The length and number of nursing bouts gradually decreases as the cubs grow older.
Mother polar bears nurse their cubs for as long as 30 months. Some cubs stop nursing as young as 18 months of age, but remain with their mothers for survival until they are 30 months old.
The average fat content of polar bear milk is 33%, similar to the milk fat of other marine mammals. For comparison, human milk has a 3-5% fat content.

Mother polar bears are extremely protective of their young, even risking their own lives in their cubs' defense.

Female polar bears are very protective of their young.

Cubs open their eyes within the first month.
The cubs begin walking while in the den at about two months. By this time, they also have thick, whitish fur and their teeth have erupted.
By the time the mother and cubs emerge from the den in late March or April, the cubs weigh 10 to 15 kg (22-33 lb.).
Mother and cubs remain around the den for about 12 more days, sometimes longer.

This enables the cubs to acclimate to the colder weather and develop their walking muscles.

During this time the cubs still spend about 85% of their time in the den, sleeping there at night.

When ready, the mother polar bear leads her cubs to sea ice. Travel is slow with frequent rest and nursing stops. A mother sometimes carries her cubs on her back through areas of deep snow or water.
Cubs begin eating solid food as soon as their mother makes her first kill on the sea ice (about three to four months of age).
The cubs grow quickly on their mother's fat rich milk and on seal blubber. By eight months of age, they weigh more than 45 kg (99 lb.).
Polar bear cubs learn to hunt by watching their mother. Cubs try hunting in their first year, but don't seem to be successful until they're over one year old. Even then, they only spend about 4% of their time hunting. By the time they're two years old they spend about 7% of their time hunting and can catch a seal every five or six days.
When her cubs are about 30 months old, a female polar bear is ready to breed again. At this time, an adult male may begin following her. Either the mother bear or the male chases away the cubs.