Experimental Studies of Coral Snake Mimicry: Generalized Avoidance of Ringed Snake Patterns by Free-Ranging Avian Predators

Abstract

Summary 1. Plasticine snake replicas were used to demonstrate that free-ranging avian predators generalize avoidance of Coral Snake ringed patterns to similar patterns, supporting the argument that the convergence on ringed and banded patterns among neotropical snakes is a result of the mimetic advantage of resembling venomous Coral Snakes. 2. The study was conducted at a tropical dry forest site in Costa Rica, where only one species of Coral Snake occurs. The Coral Snake has a tricolour (red-yellow-blackyellow-red) ringed pattern and no snakes at the site have bicolour (red-black) ringed patterns. Neither tricolour nor bicolour ringed replicas were attacked by birds, whereas an unmarked brown replica was. 3. The avoidance of the bicolour ringed pattern is attributable to generalized avoidance of Coral Snake-like patterns. No red-and-black ringed prey have been observed at the site, so birds could not have learned specific avoidance of the bicolour pattern. Historical biogeographical evidence suggests that the avifauna at the site did not evolve in the presence of red-and-black ringed snakes, so it is unlikely that birds evolved a specific innate avoidance of the bicolour ringed pattern.