Extreme variation in body temperature in a nocturnal thigmothermic lizard

Nocturnal lizards inhabiting cool temperate environments potentially experience a wide range of body temperatures (T(b)). We used radio telemetry to characterize field T(b). in a nocturnal diplodactylid gecko (Hoplodactylus maculatus) from a high-latitude (45 degrees S), sub-alpine site in Southern New Zealand. Variation in T(b) within days (diel), among clays and among different reproductive groups of this viviparous species (pregnant females, non-pregnant females and males) was measured with temperature-sensitive transmitters. We found that surgical implantation of transmitters did not have a significant effect on selected temperature on a laboratory gradient (T(sel)). Field T(b) values were examined in concert with T(sel) and microhabitat temperature in late Summer, revealing marked fluctuations of up to 30 degrees C in T(b) both within and between days. When weather conditions allowed, all reproductive groups exhibited some degree of thermoregulation, with T(b) generally elevated at least 4 degrees C above microhabitat temperature and within the bounds (central 50%) of T(sel) at the warmest times of day on most clays. Considerable thermoregulation occurred early in the day, particularly for pregnant females, and is likely to have involved some degree of direct solar basking. Temperature telemetry revealed both extreme variability in T(b) and complexity of thermoregulatory behaviour in a primarily nocturnal, thigmothermic lizard.