Thermal influence on defensive behaviours of the Eastern garter snake, Thamnophis sirtalis.

The influence of body temperature on the defensive behaviours of the Eastern garter snake was investigated. Snakes encountered in the field were grabbed by hand at mid-body to imitate the attack of a predator or were approached in the same manner but without any contact by the investigator. Behavioural responses were related to snake body and ambient temperatures. When approached without contact, snakes with higher body temperatures fled more often than snakes with lower body temperatures. Snakes that showed body flattening or flattening with mouth gaping had significantly lower average body temperatures than snakes that showed mouth gaping without flattening, those that showed neither mouth gaping nor flattening or those that showed biting (both with and without mouth gaping and flattening). The energetic constraints of a lower body temperature appear to influence the defensive behaviours of garter snakes. Colder snakes are more likely to show body flattening; warmer snakes either flee or, if they are unable to flee, are more likely to show more mouth gaping, biting or none of these behaviours.1997The Association for the Study of Animal Behaviour