Territorial red-backed salamanders can detect volatile pheromones from intruders

Previous research has shown that red-backed salamanders (Plethodon cinereus) are able to detect the unseen presence of conspecifics through pheromones left on the substratum. We conducted an experiment with territorial males to determine if they can also detect volatile (or airborne) components of pheromones from male and female intruders. By placing pheromone-laden substrata from source males and females inside or outside a perforated Petri dish, we found that males respond aggressively towards male pheromones inside the dish relative to a control and nose tapped dishes containing both source males' and females' pheroromones more than the control. We did not find evidence that residential males could differentiate between volatile components of males' and females' pheromones, but they responded more aggressively towards males' than towards females' pheromones when they had direct access to pheromone-laden substrata. These data suggest that territorial males need not patrol their small territories in search of intruders but can detect such intruders through volatile components of their pheromones. Direct contact with pheromones on the substratum may be necessary for males to differentiate between male and female intruders.