In late autumn, a female polar bear will begin to dig a winter cave. If she mated in the early spring, she will have spent the entire summer eating in earnest, as she'll need to gain at least 400 pounds (181 kg) for a successful pregnancy. The den will protect her from the harsh Arctic wind and provide a safe place to sleep. In early winter, every three years or so, she’ll give birth there, usually to one or two cubs, and they’re amazingly small. A polar bear cub weighs about a pound (454 g) at birth, and is usually about one foot (30.5 cm) long.
Go, cubs, go:
- Polar bear cubs are born blind, toothless, and with only a very thin layer of fur. They usually open their eyes within the first month, and begin walking around the den a month after that.
- Cubs grow quickly, subsisting on a diet of their mother’s fat-rich milk. They begin eating solid food when their mother makes her first kill on the sea ice. Seal is the meal of choice.
- When her cubs are about 30 months old, the female polar bear is ready to breed again. She’ll shoo the cubs away, sending them off to start lives of their own.