BEHAVIORAL THERMOREGULATION INCREASES GROWTH-RATE IN A NOCTURNAL LIZARD

We tested the hypothesis that thermoregulation increases growth rate i n nocturnal Lizards. Leopard geckos (Eublepharis macularius) maintaine d from hatching at 25 C grew at a rate of 0.11 g/day, while geckos all owed to thermoregulate at preferred body temperatures (30 C for 13.5 h per day) grew 1.5 times as fast (0.16 g/day). Long-term thermal treat ment had a significant reverse acclimation effect on preferred body te mperature (T-p): T-p was 1.2 C lower in thermoregulatory individuals t han in Chose kept at 25 C. Feeding and time of day also had significan t but minor effects on T-p. Despite their nocturnal ecology, leopard g eckos seem to be typical among Lizards in requiring a diurnal heat sou rce for maximal growth. This result provides a physiological explanati on for the observation that some nocturnal lizards thermoregulate in b urrows during the day, and may have implications for the biogeography of nocturnal ectotherms.