Microgeographic variation in the diets of garter snakes.

Diets of the terrestrial garter snake (Thamnophis elegans) and the common garter snake (T. sirtalis) were studied at 22 sites in an area of about 250 km2 in northern California, during the summers of 1978-80. Overall, T. sirtalis consumed mostly amphibian and T. elegans ate an equal mixture of amphibians, fish, and leeches. However, this was more an effect of differential distribution of the two species among sites than of habitat partitioning within sites. Site was 5 times better as a predictor of diet than was species of snake. The relative frequency of T. sirtalis at the sites was correlated with the number of amphibian species.