Thermophilic Response of the American Alligator and the American Crocodile to Feeding

Abstract

The body temperatures ( T b) and thermal behavior of juvenile Alligator mississippiensis and Crocodylus acutus were monitored in an outdoor enclosure equipped with aquatic and terrestrial thermal gradients. Both species selected significantly higher and less variable T b s when fed than when fasted. Within each species, there were considerable individual differences in T b, particularly after feeding. This variation may have been related to differences in appetite or to social factors. Fed alligators had significantly higher and less variable T b s than fed crocodiles, a difference that may reflect environmentally-related differences in their thermal strategies. In crocodilians, digestion is promoted by an increase in T b, but appetite may depend on heat availability rather than on proximate temperatures. Thermophily following feeding probably is common among reptiles, especially in aquatic and nocturnal species that are active over a wide range of T b. The notion of a single preferred T b is inconsistent with the demonstrated effects of ingestion and other factors on the thermal preferences of some reptiles, and an adjustable thermostat model is more appropriate.