Predatory attacks to the head vs. body modify behavioral responses of garter snakes

An animal's response to predatory attack may depend upon which part of its body is the focus of that attack, because of differential vulnerability to injury. Many avian and mammalian predators direct attacks preferentially toward the prey's head, so simulated attacks that do not have this focus may elicit non-natural responses. We 'pecked' 152 free-ranging adult male garter snakes (Thamnophis sirtalis parietalis) in Manitoba either on the head or the midbody, and recorded their responses. The snakes' antipredator tactics were affected not only by body size (larger snakes performed threat displays more often) and body temperature (hotter snakes were more likely to flee), but also by location of the attack. Pecks to the head generally resulted in snakes coiling and hiding their heads, often simultaneously elevating and wriggling their tails in an apparent distraction display. In contrast, pecks to the midbody stimulated either escape responses, or (in snakes that did not flee) open-mouthed threat displays. More generally, antipredator tactics may respond in flexible ways to details of the predator-prey encounter (including attributes of the habitat as well as the morphology and behavior of both participants) and hence, experimental studies need to carefully simulate such details. The part of the body under attack may be an important factor in this respect.