ABSTRACT
The term pheromone has been used to describe chemical signaling in most invertebrate and vertebrate groups, including amphibians. Pheromones are typically defined as chemical substances (e.g., a single molecule or a blend of a few molecules) that elicit an innate stereotyped behavior or developmental change in another individual of the same species (reviewed in Wyatt 2010). Pheromones may be water-soluble, volatile, or nonvolatile. In tetrapod vertebrates, they are detected by chemosensory neurons of the olfactory system, both the main olfactory system and the accessory (vomeronasal) olfactory system (Baum and Kelliher 2009). Pheromones are usually categorized according to function as releasers, primers, modulators, and alarm pheromones. Despite years of study, it is still unclear whether pheromones operate differently from nonpheromones, especially in mammals (Doty 2010). Nonetheless, many favor the use of the term pheromone, arguing that the term has intrinsic heuristic value if restricted to chemical emissions shaped by evolution to have a signaling function within a species (Wyatt 2010). Some of the controversy regarding pheromones may arise from the difficulty of translating a concept originally developed in insects to behaviorally and cognitively sophisticated mammals.
