The Feeding Ecology of Aneides flavipunctatus and Sympatric Plethodontid Salamanders in Northwestern California

Seasonal and ontogenetic variation in the diets of Aneides flavipunctatus and three sympatric plethodontids (A. lugubris, Batrachoseps attenatus, and Ensatina eschscholtzii) were studied at three localities in northwestern California. A wide variety of prey was eaten by the four species, but 75-95% of the total food volume at any one season and location was contributed by Diplopoda, Coleoptera, Isoptera, Hymenoptera, Diptera, and Collembola. In A. flavipunctatus, total food vol- ume per stomach increased with standard length to about 50 mm, then leveled off. The mean number of prey per salamander stomach declined with increasing body size and with the progres- sion of the winter rainy season, but there was no seasonal change in total food volume. Sympatric plethodontid species exhibited considerable dietary overlap, but differed in their mean and maxi- mum prey size. Analysis of stomach contents suggests that these species do not feed indiscrimi- nately: larger salamanders appear to select larger prey, and to ignore most small prey. Interspecific, ontogenetic, and seasonal differences in feeding are discussed in the light of predictions derived from an existing theoretical model of optimal foraging by a Sit-and-Wait predator.