Thermoregulatory Precision in Three Species of Whiptail Lizards (Lacertilia: Teiidae)

The mean body temperatures of the three species of Cnemidophorus were high both in the field and in the laboratory thermal gradient. Individual variation about the mean temperature was small, indicating precise thermoregulation, and the mean body temperatures (MBTs) were not significantly different for the three species. Mean body temperatures measured in the laboratory thermal gradient were slightly higher than temperatures recorded in the field. All three species displayed a similar posture when heating rapidly. The animals thermoregulated by shuttling between warm and cool areas, and this behavior resulted in sinelike fluctuations of body temperature (BT) with time. Sampling temperatures at 30-s intervals allowed analysis of short-term trends in BT and comparison of the characteristics of the sinelike curves for the three species. The average amplitude and period of the sinelike curves were compared for each species and were significantly different. The small amplitudes (less than 1.33 C) and short average periods (less than 4 min) are indicative of considerable thermoregulatory precision. The average heating and cooling rates were also computed and were found to be not significantly different, although the species were significantly different in size (both snout-vent length and weight). The parthenogenetic triploid C. uniparens was the most thermophilic, the most precise thermoregulator, and lived in the coldest habitat of the three species.