Care Bears Cheer Bear and Share Bear Unrolling A Rainbow Mug

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Mother polar bears are extremely protective of their young, even risking their own lives in their cubs' defense. Delayed implantation assures that the cub is born during the best time of the year for survival and allows the female to get into good physical condition and use her energy for nursing her newborn cubs. The average fat content of polar bear milk is 33%, similar to the milkfat of other marine mammals. For comparison, human milk has a 3-5% fat content. Most dens are on land, within 16 km (10 mi.) of the coast. In some areas, dens are more than 100 km (62 mi.) from the coast. A few polar bears make dens on the sea ice. Polar bear cubs are born November through January in a den. Mother and cubs emerge from their den in late March or April.

The most frequent litter size is two, followed by litters of one. Litters of three are less common than twins or singles, and litters of four are rare. The actual gestation length for bears is difficult to calculate. Bears can experience something called “embryonic diapause” or delayed implantation. This means that an egg is fertilized, and begins to develop into a blastocyst. The blastocyst will stop development until it implants in the uterine wall. It may be waiting for the bear to gain an appropriate amount of weight for gestation, or for an environmental factor to be just right. For this reason, a bear may technically be pregnant for 140 days but only actually gestate for 60. 3. Bears have very small babiesMost adult females give birth once every three years. In populations with access to abundant food, birth occurs once every two years. At birth, polar bear cubs weigh about 454 to 680 g (16-24 oz.) and are about 30 cm (12 in.) long. Males are born slightly larger than females. During their first few weeks of life, polar bear cubs nurse most of the time and stay close to their mother to keep warm. Females usually dig dens in snowdrifts on southerly facing slopes. Some dig earthen dens that later become covered by snow. Polar bear cubs are vulnerable for the first few months of their lives. They are easy prey for predators like arctic foxes. Staying in their dens keeps them warm, and protects them from predators. When they leave they will be about 15lbs and more difficult prey for other arctic hunters. 10. Sunbear cubs are early foragers

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). 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. Some females may seek out maternity dens as early as late August, but most enter dens in mid to late October. Dens protect newborn cubs from winter's temperature extremes. Most dens consist of a single chamber slightly elevated from a short entrance tunnel, but they can be complex with several chambers. On average, the chamber is 2 m (6.6 ft.) long, 1.5 m (4.9 ft.) wide, and 1 m (3.3 ft.) high, not much bigger than the bear. Polar bears maintain a ventilation hole through the chamber ceiling to provide fresh air.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.).