Ontogenetic Changes in the Foraging Behavior, Habitat Use and Food Habits of theWestern Aquatic Garter Snake, 'Thamnophis couchii', at Hurdygurdy Creek, Del Norte County, California

摘要

The author studied the foraging behaviors, stream habitat use, and food habits ofa marked population of western aquatic garter snakes, Thamnophis couchii, at Hurdygurdy Creek (Del Norte County, California) during the spring and summer of 1987 and 1988. Data were collected using a portable computer with a running clock so that a continuous record of behaviors and habitat use was obtained for each snake observed. Snakes were placed into three age/size classes, (neonate, juvenile, and adult) and all analyses were done among these classes. Adults foraged more actively and in a wider variety of stream habitats than either juveniles or neonates. Adults also fed on a wider variety of prey types and sizes, especially concentrating on large, stream substrate-dwelling Pacific giant salamander (Dicamptodon ensatus) larvae and neotenes. Juvenile and neonate snakes fed on prey that primarily inhabited shallow stream margins. Consumption of relatively large prey by adults and smaller prey by juveniles indicated a shift in foraging modes; from frequent feeding on small prey to infrequent feeding on large prey. These ontogenetic changes in foraging behavior, habitat use and food habits of western aquatic garter snakes are probably the result of a combination of ecological, morphological, and physiological constraints and suggest partitioning of prey and habitat.