SMALL DIFFERENCES IN DAYTIME BODY-TEMPERATURE AFFECT DIGESTION OF NATURAL FOOD IN A HERBIVOROUS LIZARD (IGUANA-IGUANA)

Juvenile iguanas were allowed to thermoregulate under each of two ''natural'', cyclic thermal regimes: under 4 hr heat/light, the mean daytime body temperature was 34.1.degree. C (SE .+-. 0.11.degree. C), with 8 hr heat/light, the mean was 36.7.degree. C (SE .+-. 0.21.degree. C). Digestion trials were performed under both thermal treatments for all iguanas, using a high-fiber food item (immature Lonchocarpus pentaphyllus leaves) normally eaten in the wild. Digestive efficiency was significantly greater at the higher body temperature. Mean transit times of particulate dietary markers did not differ significantly between the two body temperatures.