The Effect of Body Temperature and Feeding Regime on Activity, Passage Time, and Digestive Coefficient in the Lizard Uta stansburiana

In laboratory experiments, we determined the effects of body temperature and the quantity of food consumed on the probability of feeding, the passage time of food, and the digestive coefficient in the iguanid lizard Uta stansburiana. Between body temperatures of 20 and 36 C, the probability of eating increased curvilinearly with body temperature but was inversely related to the quantity of food offered. For lizards fed an unrestricted ration, the average consumption rate increased from 0 to 50 mg g⁻¹ day⁻¹ between body temperatures of 20 and 28 C and remained constant between 28 and 36 C. The passage time of food decreased curvilinearly as body temperature increased. For lizards fed an unrestricted daily ration, the mean passage time ranged from 4.6 days at 22 C to 1.2 days at 32 C. For lizards fed a restricted ration, the mean passage time ranged from 9.2 days at 22 C to 1.8 days at 32 C. Body temperature and feeding regime each had a small but significant effect on the digestive coefficient. In the restricted feeding regimes, the mean digestive coefficient ranged from 94% at 28 C to 87% at 36 C. In the unrestricted feeding regime, the digestive coefficient varied between 92% at 28 C and 84% at 36 C. We conclude that body temperature influences saurian digestive physiology primarily by affecting both the consumption rate and passage time of food while only slightly affecting the digestive coefficient.