The role of vision in the predatory behaviour of natricine snakes

Early workers concluded that ingestively naive garter snakes (Thamnophis) recognize chemical cues from their normal prey, and that such cues are sufficient to elicit prey attack, whereas visual prey cues are not sufficient. In the light of recent observations on how garter and water snakes (Nerodia) forage, new tests were made of the role of visual stimuli in the aquatic predation of several natricine species. Both experienced and ingestively naive snakes oriented to and attacked a fish model in plain water, although they made more orientations and attacks when diffuse fish odour was present in the water. Fish odour in water also elicited increased aquatic searching behaviour. Early views on the role of vision in the predation of newborn natricine snakes require modification, and there is a need for investigation of the properties of effective visual stimuli and the ontogeny of responsiveness to them.