The role of temperature in microhabitat selection by northern water snakes (Nerodia sipedon)

In an E Ontario population of northern water snakes basking activity peaked at 09:00 then declined steadily until 14:00 before increasing again. In the field, temperatures of basking snakes averaged (±SE) 26.3 ± 0.7°C, while captive snakes in a thermal gradient showed a narrower selectivity, averaging 27.7 ± 0.4°C. The temperatures of basking snakes never exceeded 33°C, even though a model snake placed in the sun reached 48°C, suggesting that the snakes were thermoregulating to prevent overheating. Water snakes based more frequently as the temperature of the air increased relative to the water. Temperature influenced microhabitat selection independently of circadian patterns. When in water, snakes tended to frequent habitats where leopard frogs Rana pipiens, a common prey species, were most abundant, ie prey distribution may also be an important component of water snake habitat selection. -from Authors