An alternative hypothesis for the primary function of a proposed mate assessment behaviour in red-backed salamanders

Using a laboratory experiment, we tested the hypothesis that faecal inspection and squashing behaviours by female red-backed salamanders, Plethodon cinereus, function in a context other than mate assessment, in this case foraging. Because only female P. cinereus squash faecal pellets, other studies have hypothesized that the faecal squashing is a mate assessment behaviour. During the courtship season, we exposed gravid female P. cinereus maintained on a ‘high-quality’ or ‘low-quality’ diet, to the faecal pellets of male and female conspecifics fed ‘high-quality’ diets. Female diet had no effect on activity level, and, overall, P. cinereus showed greater interest in male-marked substrates than female-marked substrates. However, female diet had a large effect on faecal inspection and squashing behaviours, and females showed similar inspection and squashing rates towards both male and female faecal pellets. These results suggest that faecal squashing does not function primarily in mate assessment, but rather as a means for female P. cinereus to gain information about prey availability. We propose that male P. cinereus have evolved to exploit female faecal inspection and squashing behaviours (sensory exploitation) to attract foraging females into areas to increase male encounter rates with females.