Circadian Activity Patterns in the Desert Iguana, Dipsosaurus dorsalis

Abstract

Daily locomotor activity patterns of the desert iguana, Dipsosaurus dorsalis, were recorded under light (L):dark (D) conditions of 12L:12D. These animals produced daily patterns which (a) were monophasic, (b) showed a response of the lizard to onset of light. Both of these characteristics accord with those reported for other day-active animals. The laboratory-recorded daily activity rhythms correlate remarkably well with the field behavior of movement in burrows before emergence, basking early in the activity period, foraging, and retreating to shade or burrow in the later part of the activity period. It is likely that the laboratory-recorded daily activity patterns would change according to the temperature in the activity chamber. These changes would correlate with the seasonal variations in daily activity patterns reported in field studies. Wide individual differences in phase-angle relationships between activity onset and light onset among lizards was observed. It is possible that these differences are due to one or more of the following factors; (a) the low intensity difference between the light and dark phases of the cycle, (b) individual differences in preferred body temperature, and/or (c) individual differences in daily light requirements.