READ: Animals and Energy
Migration and Hibernation
Yearly Cycles
An example of a behavior with a yearly cycle is hibernation. Hibernation is a state in which an animal’s body processes are slower than usual, and its body temperature falls. An animal uses less energy than usual during hibernation. This helps the animal survive during a time of year when food is scarce. Hibernation may last for weeks or months. Animals that hibernate include species of bats, squirrels, and snakes.
Most people think that bears hibernate. In fact, bears do not go into true hibernation. In the winter, they go into a deep sleep. However, their body processes do not slow down very much. Their body temperature also remains about the same as usual. Bears can be awakened easily from their winter sleep.
Another example of a behavior with a yearly cycle is migration. Migration is the movement of animals from one place to another. Migration is an innate behavior that is triggered by changes in the environment. For example, animals may migrate when the days get shorter in the fall. Migration is most common in birds, fish, and insects. In the Northern Hemisphere, many species of birds, including robins and geese, travel south for the winter. They migrate to areas where it is warmer and where there is more food. They return north in the spring. A flock of migrating geese is pictured below (figure below).
These geese are flying south for the winter. Flocks of geese migrate in V-shaped formations.
Some animals migrate very long distances. The map shown below shows the migration route of a species of hawk called Swainson’s hawk (figure below). About how many miles do the hawks travel from start to finish? Are you surprised that birds migrate that far? Some species of birds migrate even farther. Whales also are known to migrate thousands of miles each year to take advantage of warmer waters in the winter months. The great migration of millions of zebra, wildebeest and other antelope in East Africa also occurs yearly. Each year around 1.5 million wildebeest and 300,000 zebra (along with other antelope) go in search of food and water, traveling a distance of around 1800 miles.
The migration route of Swainson’s hawk starts in North America and ends in South America. Scientists learned their migration route by attaching tiny tracking devices to the birds. The birds were then tracked by satellite. On the migration south, the hawks travel almost 5,000 miles from start to finish.
Birds and other migrating animals follow the same routes each year. How do they know where to go? It depends on the species. Some animals follow landmarks, such as rivers or coastlines. Other animals are guided by the position of the sun, the usual direction of the wind, or other clues in the environment.