INFLUENCE OF PREGNANCY ON THE THERMAL BIOLOGY OF THE LIZARD, SCELOPORUS-JARROVI - WHY DO PREGNANT FEMALES EXHIBIT LOW BODY TEMPERATURES

1. Selected body temperatures of female lizards, Sceloporus jarrovi, w ere measured on a photothermal gradient during late pregnancy and agai n when postpartum, and pregnant females were subjected to one of three fluctuating temperature regimes that simulated body temperatures of ( 1) pregnant females, (2) postpartum females or (3) allowed normal ther moregulation. 2. Overall, females selected lower body temperatures whe n pregnant (mean = 32.0 degrees C) than when postpartum (mean = 33.5 d egrees C). 3. Females regulated body temperature more precisely when p regnant than when postpartum as judged by their smaller variances in b ody temperature throughout the day. 4. When pregnant, females selected a lower mean maximum body temperature (mean: pregnant = 32.8 degrees C; postpartum = 34.5 degrees C) than when postpartum, but selected mea n minimum body temperatures did not differ. 5. None of the experimenta l temperature treatments was detrimental to pregnant females. Female b ody length increased during pregnancy but the rate of increase did not differ among treatments. Moreover, length-adjusted body mass of postp artum females did not differ among treatments. 6. Pregnant females tha t experienced postpartum body temperatures produced neonates that were smaller in body mass and length than pregnant females that experience d pregnant body temperatures and females that were allowed to thermore gulate. 7. For neonates resulting from the postpartum body temperature treatment, the disparity in the body length, but not mass, was still observed at 9 days of age, although survival and growth of neonates wa s high and did not differ among treatments. 8. The results demonstrate that pregnant females could maintain higher postpartum body temperatu res without compromising their physical condition, but select relative ly low body temperatures, presumably to avoid decrements in offspring fitness.