Aggressive mimicry in neonates of the sidewinder rattlesnake, Crotalus cerastes (Serpentes: Viperidae): stimulus control and visual perception of prey luring

Aggressive mimicry in vertebrates remains understudied relative to other categories of mimetic systems, such as Batesian mimicry. Prey attraction through caudal luring (CL) is a type of aggressive mimicry that constitutes a tripartite relationship in which a predator (mimic, S2), typically a snake, produces a highly specific tail display in the presence of a prey species (receiver or operator, R) to produce a resemblance to a prey animal (model, S1), such as a worm or insect, that the receiver mistakes for food and attempts to capture. Most reports of CL in snakes, however, are not hypothesis-based and provide limited information on the cognitive interplay between predator and prey. In two experiments, CL was studied using a large sample (N = 40) of neonatal sidewinder rattlesnakes (Crotalus cerastes) and lizards (N = 12 species) to investigate stimulus control and visual perception. In experiment 1, CL was elicited in 110 trials using lizards that were either syntopic (N = 6 species) or nonsympatric (N = 6 species) to C. cerastes, and CL occurred at a significantly greater frequency when using syntopic taxa. Similarly, syntopic lizards were attracted to luring snakes significantly more than their nonsympatric counterparts. The presence of CL in C. cerastes was not ubiquitous and we provide preliminary evidence that this behaviour varies geographically and thus has a genetic basis. In experiment 2, a potential predator (live toad) was introduced to subjects that had been stimulated to lure by means of a prey-dummy and, in all (N = 8) trials, there was an immediate shift in the behaviour of the snakes. The most notable changes were termination of CL and a transition to species-typical defensive displays, which included rapid tail vibration and audible rattling in individuals with two (or more) rattle segments. We discuss future directions of CL research in snakes, especially with regard to expanding the types of cognitive tests.