When cold winter comes, food can be very hard to find. Plants stop growing and many bugs disappear, so animals need clever ways to survive. Two of these ways are called migration and hibernation.

Migration means traveling a long way to a warmer place where there is more food. Many birds fly south every fall and come back north in the spring. This long trip helps them find meals all winter long.

Birds are not the only travelers. Some whales, butterflies, and even caribou migrate too. Monarch butterflies fly thousands of miles to a warm forest, which is amazing for such a tiny insect.

Hibernation is different, because the animal stays put and goes into a very deep sleep. During hibernation, an animal's heartbeat slows down and its body cools, so it uses very little energy and does not need to eat.

Before winter, a hibernating animal like a groundhog eats lots of food to store fat in its body. That stored fat keeps it alive while it sleeps through the coldest, hungriest months.

Both migration and hibernation solve the same problem in different ways. One animal leaves to find food somewhere warmer, and the other stays home and sleeps until the food comes back in spring.