Thermal regimes and diel activity patterns of four species of small elapid snakes from south-eastern Australia

Abstract

Two of the most basic biological attributes for any ectothermic animal are the times of day that it is active and the body temperatures that it exhibits. Published studies on reptile biology display a heavy bias towards diurnal lizards from Northern Hemisphere habitats. To help redress this imbalance, we quantified thermal regimes and activity times in four species of small Australian elapid snakes. Mean selected body temperature in a thermal gradient was affected by the time of testing (i.e. night v. day), with snakes choosing higher body temperatures at night than by day. In outdoor enclosures, whip snakes (Demansia psammophis) were shuttling heliotherms active only during daylight hours at relatively high body temperatures; in a laboratory thermal gradient these animals selected high body temperatures (mean 31.3°C during the day and 33.2°C at night). The other three taxa – golden-crowned snakes (Cacophis squamulosus), small-eyed snakes (Cryptophis nigrescens) and marsh snakes (Hemiaspis signata) – were active mostly at night at relatively low body temperatures, and selected low body temperatures in a thermal gradient (18.1–23.4°C). Thus, mean selected body temperatures differ substantially among sympatric elapid species in south-eastern Australia and are correlated with times of activity.