RESPONSES OF ECOLOGICALLY DISSIMILAR POPULATIONS OF THE WATER SNAKE Natrix s. sipedon TO CHEMICAL CUES FROM PREY

Three populations of the water snake, Natrix s. sipedon, were tested for their responses to surface water extracts prepared from various prey species. It was clearly shown that these snakes can distinguish between different prey genera on the basis of chemical cues alone. Adult snakes caught at a fish hatchery where goldfish (Carassius auratus) were abundant responded most to goldfish extract, as did laboratory-born snakes reared on goldfish for one year. However, snakes caught in a relatively undisturbed mountain stream environment and naive young born to a mountain female responded more to the extracts of various sympatric mountain fish and amphibians. The evidence indicates that newborn snakes have genetic predispositions for sympatric species of the classes of prey normally eaten. These preferences can be enhanced or inhibited during ontogeny.