Neonatal plasticity and adult foraging behavior in garter snakes (Thamnophis sirtalis) from two nearby, but ecologically dissimilar, habitats

The widely distributed Common Gartersnake (Thamnophis sirtalis) thrives in it variety of environments and preys upon a diversity of species. Phenotypi c plasticity (including learning), as well as genetic diversity, may, under lie the success or this species, We examined how different types of feeding experience influence the ontogeny, of foraging behavior in garter snakes f rom two populations with different adult diets (earthworm or diets) living on Beaver Island in Lake Michigan. Times to approach, capture, handle, and swallow prey were recorded in controlled laboratory settings. In Experiment I, neonatal snakes reared on fish, earthworms, or a mixed diet were tested for feeding skills at their first feeding, and at 5 subsequent intervals a fter feeding experience and diet-switching over a period of nearly 8 months . Snakes in all three groups decreased their latencies to consume prey afte r feeding experience and there were some litter, but no site or sex, differ ences. Snakes fed initially, on,worms were slow at consuming fish upon diet switching, whereas snakes that initially fed on fish rapidly consumed worm s upon their first feeding. Feeding skills for initial prey were retained f ollowing the diet-switching phase. Experiment II determined the effects of long-term feeding experience on the abilities, of field-caught adult snakes to detect, capture, and consume frogs, fish, and worms. Most foraging meas ures differed for ill Olive prey, but there were few site differences and n o sex differences. The effects of prior feeding experience appear to be les s evident for adults than for neonates, which may be due to the effects of changing predator-prey body size relationships, changes in prey availabilit y, or to constraints of the captive testing environment. Although populatio ns on the island cat different prey, there is little evidence for genetic d ifferentiation in foraging behavior during the several thousand years that the island has existed.