ANTIPREDATOR BEHAVIOR OF HATCHLING SNAKES - EFFECTS OF INCUBATION-TEMPERATURE AND SIMULATED PREDATORS

All animals that are exposed to predators must distinguish dangerous f rom nondangerous threats and respond correctly. In reptiles, emerging hatchlings are vulnerable to a wide range of predators, particularly i f they emerge during daylight. In these experiments I tested the respo nse of pine snake, Pituophis melanoleucus, hatchlings incubated at 22- 23, 27-28, or 32-33 degrees C to visual and vibratory stimuli to exami ne antipredator behaviour. Emerging hatchlings were exposed to one of five conditions: (1) hawk model, (2) white head model. with no facial features, (3)white head model with black eyes, (4) a person, or (5) a vibration without a visual stimulus. I tested the null hypotheses of n o differences in response as a function of predator type or incubation temperature. Emergence behaviour when undisturbed was affected by inc ubating temperature, and antipredatory behaviour was affected by both predator type and incubation temperature. Pine snake hatchlings respon ded more protectively (withdrawal into tunnels) than defensively (stri king), responded with less intensity to a vibration compared with visu al predator stimuli, and required longer to respond to a head model wi thout eyes than to all other predator types. Given the relatively smal l size of hatchlings, it is adaptive for them to withdraw into the nes t rather than attack a predator. Hatchlings from eggs that were incuba ted at medium temperatures required less time to emerge from their und erground nests when undisturbed, and had stronger protective responses than snakes incubated at other temperatures. These results suggest th at hatchlings incubated at medium temperatures are generally less vuln erable to predators than hatchlings incubated at higher or lower tempe ratures. (C) 1998 The Association for the Study of Animal Behaviour.