A pheromone mechanism for swaying female mate choice: enhanced affinity for a sexual stimulus in a woodland salamander

Traditionally, male signals have been thought to function in satisfying female choice by conveying meaningful information about a potential mate. However, the male signal, rather than merely providing raw material for female evaluation, may actively modulate a female’s intrinsic preferences or decision-making capabilities in favour of a given male. We propose two broad mechanisms by which male signals could modulate female behaviour: (1) specific augmentation of sexual motivation or (2) heightened general arousal. Specifically, we investigated the ability of a generic male pheromone mix to elicit changes in general activity or affinity for different classes of stimuli in female terrestrial salamanders (Plethodon shermani). Attraction to male olfactory stimuli was significantly increased by pheromones, but attraction to visual stimuli and nonsexual olfactory stimuli remained unaffected, as did locomotor activity. These results are consistent with the hypothesis that sex pheromones activate specific behavioural subsystems associated with augmented sexual motivation. This pheromone action may still function within the context of information-transfer signalling, for example, if pheromones influence female choice by affecting (1) sensory processing of relevant stimuli, (2) the value assigned to a set of sexual stimuli, or (3) the criteria used to decide whether to mate.