STIMULUS-CONTROL OF DEFENSIVE BEHAVIORS OF GARTER SNAKES (THAMNOPHIS-SIRTALIS) - EFFECTS OF EYE SPOTS AND MOVEMENT

The purpose of these experiments was to examine the effects of eye spo ts and stimulus movement as mediators of antipredator responses in gar ter snakes. In Experiment 1, 13 Eastern garter snakes (Thamnophis sirt alis) at 6-8 weeks of age were confronted with a series of threatening models that varied in the configuration of the eyes (artificial glass eyes, circular black spots, elongated black bars, or no eyespots). Th ere were significant differences in the number of strikes elicited by the models, and the model with realistic glass eyes elicited the most strikes. In Experiment 2, we examined the effects of erratic and consi stent stimulus movement on defensive behavior in 12 garter snakes at 1 2-16 weeks of age. The snakes delivered significantly more strikes to an erratically moving model than to a model oscillated at a regular ra te.