Amphibious behavior of Alligator mississippiensis: roles of a circadian rhythm and light.

Juvenile American alligators in outdoor pens moved out of and into the water at sunrise and sunset, respectively. When the natural light cycle was extended with artificial illumination, these movements gradually shifted into phase with the altered light cycles; therefore, the amphibious behavior was modulated by a circadian rhythm cued by light. Movement between land and water was characterized by a decrease in body temperature, which suggests that it is was not simply a proximate heat-seeking response. After the movements had been in phase with the altered light cycles for a time, they spontaneously shifted back into phase with the natural light cycl. A changing response to light is viewed as an adaptation to seasonal changes in heat availability.