Chemosensory Responses of Salamanders to Snake Odors

Abstract

Some prey species avoid predators using flight or freeze responses, while some may show either response depending on the ecological context. Consequently, predator avoidance may be risk-sensitive, and the level of activity may be an important risk-specific component of the avoidance response. Red-backed salamanders, Plethodon cinereus, were exposed at times of low risk (night) and high risk (day) to the substrate odors of predatory garter snakes (Thamnophis sirtalis) maintained on low risk (goldfish) and high risk (redbacked salamander) diets. Salamanders maximally avoided snake odors over blank substrates in all except the lowest risk treatment, which was not avoided, and thus they appeared to show a threshold (all or none) response to snake odors. However, the concurrent activity level of the salamander (degree of movement during avoidance) showed small scale increases with each risk increment from the lowest risk treatment (goldfish diet at night) to the highest risk treatment (salamander diet during day). There was no evidence of a freeze response during predator avoidance. Partial ”dissociation” of avoidance and activity at night, i.e. no change in avoidance with a change in activity level, or vice versa, is discussed in the context of the biology of P. cinereus. Future studies of predator avoidance behavior should closely examine prey activity for clues to the diversity and intensity of risks that ultimately shape predator avoidance.