Detection of the Sexual Identity of Conspecifics through Volatile Chemical Signals in a Territorial Salamander

Territorial red‐backed salamanders (Plethodon cinereus) have been shown to use nonvolatile chemical signals in both territorial defense and to convey a variety of information to conspecifics. We investigated whether or not red‐backed salamanders could determine the sexual identity of conspecifics through volatile chemical signals, and we explored their use in the context of territorial defense. We exposed male and female red‐backed salamanders to four experimental treatments (i.e. filter papers that had been scent marked by male or female conspecifics for 1 and 5 d) and two control treatments (i.e. unscented filter papers for 1 and 5 d tests). The focal salamanders were prevented from physically accessing the scent marked filter papers and, presumably, some of the substrate scent marks had volatile components that were detected and interpreted by the focal salamanders. Both male and female red‐backed salamanders spent significantly more time in threat displays when they were exposed to volatile chemical signals from same‐sex conspecifics than they did toward similar signals from opposite‐sex conspecifics. A similar statistical pattern was observed for the amount of chemosensory sampling exhibited by focal red‐backed salamanders. From these results, we infer that red‐backed salamanders can determine the sexual identity of conspecifics through volatile chemical signals, some of which may be used in territorial defense. Further, such airborne pheromones may influence the spatial organization of salamander territories on the forest floor.