Chemosensory responses to chemical and visual stimuli in five species of colubrid snakes

Abstract

Snakes utilize chemical and visual stimuli during predation, however the emphasis on these cues and which cues are used to initiate predation varies among species. For example, rattlesnakes using the ambush strategy rely on chemical cues to locate an ambush station, then visual and thermal cues to initiate envenomating strikes, then chemical cues again to track prey. By contrast, many natricine snakes use chemical cues to initiate predation, increasing the rate of tongue flicking regardless of whether visual cues are present. The present study examined the individual and interactive effects of chemical and visual stimuli of prey on the predatory behavior of five snake taxa representing three feeding guilds. Bull snakes ( Pituophis catenifer ), Eastern Corn snakes ( Pantherophis guttatus ), and Midland Rat snakes ( Scotophis spiloides ) have a diet primarily consisting of mammals; Western Fox snakes ( Mintonius vulpina ) prey primarily on bird eggs; and Common Kingsnakes ( Lampropeltis getula ) prey equally on mammals and reptiles. Three patterns of response to chemical and visual stimuli of the test prey ( Mus musculus ) were observed. Mammal specialists responded to chemical cues. Fox snakes responded to visual cues, but not to chemical cues. Kingsnakes exhibited increased rates of tongue flicking in response to both chemical and visual stimuli. This study suggests correlations between the evolution of prey preference, foraging ecology and the utilization of chemical or visual stimuli by snakes.