From the Winter 2010 Conservationist for Kids
Time for Bed
By Ann Pedtke
Put on your pajamas, have a little bedtime snack, crawl into bed and pull up the covers. Nighty-night, see you in the morning! But what if "bedtime" is fall, and the time to wake is spring? For animals that hibernate, bedtime preparations are not like yours. The clock doesn't signal bedtime. Instead, shorter days, colder temperatures and less available food may work together to trigger hibernation.
That bedtime snack mentioned earlier is actually weeks, possibly months, of eating lots of food to put on body fat. The hibernating animal will rely on this stored fat as food. (Some smaller mammals wake up for short periods during hibernation and eat from food stored in their underground burrows, in addition to using up body fat.)
A Cozy Bed
For frogs and turtles, the mud at the bottom of the pond is a cozy winter spot. It's even above freezing, since the water temperature may remain around 40 degrees, insulated from the cold air by a layer of ice.
If the pond bottom isn't a good option, how about underground? Many mammals, plus snakes, toads, and salamanders, spend the winter underground in rocky crevices, burrows, or under logs and leaves on the forest floor. Bats go underground in caves. If they go far enough underground, animals can get below the "frost line," below where the ground is frozen and the earth is still soft. Pile a blanket of snow on top for extra cover, and it's pretty cozy. Tucked away in a cocoon, many insects provide their own blanket.