LaDue, C. A., Schulte, B. A. 2021. Pheromonal enrichment in the zoo: An empirical approach with Asian elephants (Elephas maximus). Applied Animal Behaviour Science 235, 105228.
The use of odors is a popular form of sensory enrichment, yet few studies have investigated the longer lasting effects of biologically relevant chemical signals like pheromones. Asian elephants (Elephas maximus) are unique because they are commonly held in zoos and utilize two single-compounds to synchronize reproduction: frontalin (a pheromone produced by male elephants in musth) and (Z)-7-dodecenyl acetate (Z7-12:Ac, a pheromone produced by female elephants around ovulation). While Asian elephant chemical signaling dynamics have been well-studied, no reports exist on the broader behavioral effects (i.e., primer effects) of either of these pheromones. The purpose of this study was to describe the primer effects of both frontalin and Z7-12:Ac for potential enrichment applications. We bioassayed 50 elephants at 10 zoos using synthetic versions of these two pheromones that replicated the concentrations at which they are produced naturally. We found that behavioral diversity in response to these pheromones was influenced both by the degree of exposure to the chemicals and by properties of the receiver, such as sex, sexual experience, age, and social access, with models that included all or most of these factors explaining much of the variation in the bioassay data for frontalin (R2(c) = 0.42) and Z7-12:Ac (R2(c) = 0.59). Furthermore, both males and females exhibited distinct changes in activity levels in the presence of frontalin or Z7-12:Ac, with specific behavioral differences noted. For instance, frontalin stimulated increased activity (and decreased inactivity) among female elephants (P < 0.001). Foraging (P = 0.029) and walking (P = 0.001) increased when males were exposed to frontalin, but it also stimulated increased time spent engaged in stationary stereotypy (P < 0.001). On the other hand, Z7-12:Ac encouraged greater activity levels in female (P < 0.001) and male (P = 0.010) elephants. These results support the use of pheromones as enrichment opportunities for elephants, and suggest appropriate chemical signals should be considered for other species. Because these compounds hold biological, ecological, and/or evolutionary salience, they can have long-lasting effects and are particularly relevant to long-term management strategies. In conjunction with other forms of sensory enrichment—including biologically novel odors—pheromones have the potential to enhance the wellness of zoo-housed species.