Reproductive influences on behavioral thermoregulation in the lizard, Sceloporus cyanogenys

Abstract

Several thermoregulatory parameters were measured for female and male Sceloporus cyanogenys during one reproductive season. Body temperatures, body temperature thresholds for thermoregulatory behavior, and thermoregulatory activity all declined to a minimum at pregnancy as lizards progressed through preovulatory and ovulatory states. Marked increases in these parameters occurred in post parturient lizards. Males were not significantly different from post parturients. Progesterone administration significantly depressed body temperature levels and body temperature thresholds for thermoregulatory behavior, but not thermoregulatory activity in another post parturient group. Callard detected greater amounts of plasma progesterone in pregnant S. cyanogenys compared to other reproductive states [6]. Therefore, it is proposed that during pregnancy progesterone functions to modulate thermoregulatory behavior and energy expenditure. These results support the idea that the sensitivity of the thermostatic components to internal and external environmental factors determines a labile rather than a fixed regulated body temperature in some reptiles.