The thermal biology of digestion in rubber boas (Charina bottae): physiology, behavior, and environmental constraints.

Coadaptation predicts a match between the thermal physiology and thermoregulatory behavior of reptiles. We tested this prediction by studying the digestive biology of rubber boas (Charina bottae). We measured the thermal dependence of gastric digestive rate and passage rate in rubber boas from 10 degrees C to 35 degrees C. We examined the effect of digestion on their thermal preference by measuring the temperatures of C. bottae in a thermal gradient before and after feeding. While the passage rates calculated from the body temperatures of digesting snakes were higher than the passage rates calculated from the body temperatures of nondigesting snakes, there was no difference in calculated digestive rates. These results indicate that the thermoregulatory behavior of C. bottae may be more tightly correlated with factors affecting passage rate than with digestive rate alone. Results of simulating the constraints of the thermal environment on the digestive biology of C. bottae showed that digestion would take more than twice as long in the spring as in the summer. In addition, during the summer, snakes thermoregulating as digesting snakes would pass food 12% faster than those thermoregulating as nondigesting snakes. These results demonstrate how interpretation of laboratory studies can be improved when combined with measurements of appropriate environmental conditions.