Animal Behavior

Behavioral Ecology

What is a biological clock?

A biological clock controls a biological rhythm; it involves an internal pacemaker with external (usually environmental) cues. An environmental signal that cues the clock for animals is called a zeitgeber, a German term meaning “time-giver.” Examples of zeitgebers include light and dark cycles, high and low tides, temperature, and food availability. A biological rhythm is a biological event or function that is repeated over time in the same order and with a specific interval. Biological rhythms are evident when an animal’s behavior can be directly correlated to certain environmental features that occur at a distinct frequency. Biological clocks control animal behaviors such as when migration, mating, sleep, hibernation, and eating occur. Some examples of biological rhythms: A tidal rhythm would include the oysters (feeding) and fiddler crab (mating and egg laying)— 12.4 hours; circadian rhythm would include the fruit fly (an adult emerging from a pupa)—twenty-four hours; a circannual rhythm, such as a woodchuck coming out of hibernation or a robin migrating or mating—twelve months; or an intermittent rhythm, such as a lion that needs to feed because it’s hungry, or a river fish called a shiner that reproduces when the river floods—going from days to several years.


This is a web preview of the "The Handy Biology Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App