Polymorphism and Geographic Variation in the Feeding Behavior of the Garter Snake Thamnophis elegans.

Geographic variation in behaviors that influence resource utilization is a key component in current ecological theory, but the phenomenon has been poorly documented. Propensity to attack slugs varies geographically in a western garter snake, Thamnophis elegans. Many naive, newborn snakes from inland localities in California refuse to eat slugs. In contrast, virtually all naive young from coastal localities eat slugs. There is, however, no demonstrable polymorphism or geographic variation for propensity to eat anurans. Both coastal and inland snakes consistently eat anurans.