Care Bears Cheer Bear and Share Bear Unrolling A Rainbow Mug

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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 babies Most adult females give birth once every three years. In populations with access to abundant food, birth occurs once every two years. Because of the bears' body heat and snow insulation, the den stays warmer than the outside air temperature. Scientists are now using this heat to detect bears with forward-looking infrared technology (FLIR).

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. 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. Grizzly bears cubs start eating solid foods at a few months old, but they will continue nursing for as long as 3 years. The mother bear will decide when she wants her cubs to stop nursing. This is usually when she is ready to mate again. image: Pixabay.com 6. Bears use trees as babysitters for their cubs 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 polar bears are extremely protective of their young, even risking their own lives in their cubs' defense.

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

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. Once mated, females begin depositing fat in preparation for cubbing. Females need to gain at least 200 kg (441 lb.) for a successful pregnancy. 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. Females usually dig dens in snowdrifts on southerly facing slopes. Some dig earthen dens that later become covered by snow.