Concentration‐dependent chemosensory responses towards pheromones are influenced by receiver attributes in Asian elephants

The physical structure of a signal is not sufficient to determine its meaning. For chemical signals between conspecifics, this concept is termed “pheromonal parsimony.” The function of a compound depends not only on its molecular structure but also on its context, which can include signal concentration and various receiver attributes. We sought to investigate the contextual flexibility of chemosensory responses through bioassays with Asian elephant (Elephas maximus) sex pheromones of various concentrations (frontalin, from males, and (Z)‐7‐dodecenyl acetate Z7‐12:Ac], from females). We hypothesized that elephants would respond stronger to higher concentrations, especially towards the opposite‐sex pheromone, and that receiver age and sexual experience would modify responses. We examined responses of 73 captive elephants to both compounds. Pheromone concentration impacted the rate of chemosensory response, which was further modified by the sex, age and/or sexual experience of the receiver. Response rates increased with concentration for each compound across both sexes. Experience shaped male responses with older, physiologically primed males responding more often. The interaction between experience and age affected female response to frontalin, but not to Z7‐12:Ac. Furthermore, response thresholds were modified by sexual experience in most cases: experienced animals generally had lower thresholds than inexperienced animals. Elephants responded to each solution according to its perceived relevance, including concentration. These results also indicate that receiver attributes (e.g., sex, age and sexual experience) may modify seemingly fixed chemosensory responses and further emphasize the flexibility of vertebrate communication systems.