Balanced on a rock in the middle of a river, a black bear lowers her head to the water and tries to catch a fish. She's spent the summer eating berries and roots. Now she's eating all the fish she can catch. She needs fat to put on weight and make milk for newborn bears this winter.

Black bears live throughout most of North America, including northern Mexico. They usually live in forests and are excellent tree climbers. Although they are called black bears, they can be blue-gray, brown, or even white. Black bears are not picky eaters. Their goal is to store up as much fat as possible before their winter sleep.

In late November and early December, black bears head to their caves to sleep away the winter, or hibernate (冬眠). Their body temperature is lowered, and their breathing slows down while they live off the huge amounts of body fat they stored up during the summer and fall. This way, they don'thave to go out and look for food in the cold.

Male black bears leave their caves around mid-March, but females stay a little longer. That's because they give birth around January and want to give their kids time to grow bigger before heading back outside in the early spring.

Little black bears stay with Mom for one to three years while she teaches them how to live in the wild. Then, when they're ready, they head off to survive in the woods alone—until they start a family of their own.