Male salamanders remember individuals based on chemical or visual cues

The use of multiple cues can enhance the detection, recognition, discrimination, and memorability of individuals by receivers. We conducted two experiments, using only males, to test whether territorial red-backed salamanders, Plethodon cinereus, could use only chemical or only visual cues to remember familiar conspecifics. In both experiments, focal males spent significantly more time threatening unfamiliar than familiar male intruders. They also chemoinvestigated the filter paper containing chemical cues of unfamiliar intruders more often than that of familiar intruders. These results suggest that red-backed salamanders can use both chemical and visual cues to recognize familiar individuals, allowing them to distinguish between less threatening neighbours and more threatening intruders in the heterogeneous forest floor habitat, where visual cues alone would not always be available.