Seasonal shifts in the thermoregulatory behaviour of Australian blacksnakes, Pseudechis porphyriacus (Serpentes: elapidae)

1. Activity patterns, movements and thermoregulation of 27 adult blacksnakes containing miniature temperature-sensitive radiotransmitters were monitored in spring and summer in a montane area of eastern Australia. 

2. Within each season, mean selected body temperatures were similar in the two sexes, regardless of reproductive status. 

3. In spring, male temperatures tended to be more variable than those of females, because the long-range movements of males precluded precise thermoregulation. 

4 .Although ambient (air) temperatures were higher in summer than in spring, the reverse was true of body temperatures: both male and female snakes were approx. 5°C cooler in summer than in spring. 

5. Snakes were less active in summer than in spring, and were cooler in summer even when they were active. 

6. We attribute the decreased activity levels in summer to drought, which apparently depressed availability of prey (frogs), and hence foraging by the snakes. Under such circumstances, the metabolic costs of maintaining high body temperatures may exceed the likely benefits of unproductive foraging.