Behavioral Cycles

How do environmental changes affect animal behavior?

The daily changeover on coral reefs is an example of regular cycles in nature. Many animals respond to periodic changes in the environment with daily or seasonal cycles of behavior. Behavioral cycles that occur daily, like those on coral reefs, are called circadian (sur KAY dee un) rhythms. You sleep at night and attend school during the day in another example of a circadian rhythm.

Other cycles are seasonal. In temperate and polar regions, for example, many species are active during spring, summer, and fall, but enter into a sleeplike state, or dormancy, during winter. In mammals, dormancy is called hibernation. Dormancy allows an animal to survive periods when food and other resources may not be available.

Another type of seasonal behavior is migration, the seasonal movement from one environment to another. Many species of animals migrate—often over huge distances. Figure 29–7 shows the long migration of green sea turtles. Migration allows animals to take advantage of favorable environmental conditions. For example, many songbirds live in tropical regions where temperatures are moderate and food remains available during northern winters. When these birds fly north in the spring, they take advantage of seasonally abundant food and find space to nest and raise their young.

FIGURE 29–7 Seasonal Behavior of Green Sea Turtles Each year, green sea turtles migrate back and forth between their feeding grounds on Brazil's coast and their nesting grounds on Ascension Island.