EFFECT OF TEMPERATURE ON DIGESTIVE EFFICIENCY IN HERBIVOROUS LIZARD, DIPSOSAURUS-DORSALIS

There is a significant correlation between body temperatures of the lizard D. dorsalis and the proportion of ingested food utilized. At temperatures of 33, 37 and 41.degree. C apparent digestibility coefficients (ADC) were 54.3%, 62.8% and 69.5%, respectively. Lizards kept at 28.degree. C did not pass food beyond the stomach and died, while lizards cycled between 28.degree. C and 41.degree. C had an ADC predicted for the mean of those temperatures. When corrected for fibrous material, these values became 70%, 82% and 89%, which agree well with other herbivorous lizards on a low fiber diet. Field passage rates of lizards fed markers correspond to recorded laboratory passage time of 2-3 days. Thermoregulation by D. dorsalis at higher body temperatures within its activity range increases the digestive efficiency. The net energetic advantage of this relationship remains uncertain because of unknown routine energetic costs and energy processing rates at different temperatures.