Appeasing Pheromones for the Management of Stress and Aggression during Conservation of Wild Canids: Could the Solution Be Right under Our Nose?

Abstract

Thirty-six species of canid exist globally, two are classified as critically endangered, three as endangered, and five as near threatened. Human expansion and the coinciding habitat fragmentation necessitate conservation interventions to mitigate concurrent population deterioration. The current conservation management of wild canids includes animal translocation and artificial pack formation. These actions often cause chronic stress, leading to increased aggression and the suppression of the immune and reproductive systems. Castration and pharmaceutical treatments are currently used to reduce stress and aggression in domestic and captive canids. The undesirable side effects make such treatments inadvisable during conservation management of wild canids. Pheromones are naturally occurring chemical messages that modulate behaviour between conspecifics; as such, they offer a natural alternative for behaviour modification. Animals are able to distinguish between pheromones of closely related species through small compositional differences but are more likely to have greater responses to pheromones from individuals of the same species. Appeasing pheromones have been found to reduce stress- and aggression-related behaviours in domestic species, including dogs. Preliminary evidence suggests that dog appeasing pheromones (DAP) may be effective in wild canids. However, the identification and testing of species-specific derivatives could produce more pronounced and beneficial behavioural and physiological changes in target species. In turn, this could provide a valuable tool to improve the conservation management of many endangered wild canids.

Keywords: African wild dog; aggression; appeasing pheromone; conservation; immune suppression; metapopulation management; reproductive suppression; stress; wild canid; wolf.

Figure 1

Schematic representation of sensory projections in the (a) main olfactory epithelium (MOE) and (b) vomeronasal organ (VNO). (a) Within the MOE, olfactory sensory neurons in the olfactory epithelium expressing the same specific odorant receptor have axons that innervate to the same glomerulus (represented by the different colours green, blue, and purple), which in turn excite specific mitral cells to act on specific brain regions. (b) Within the VNO, sensory neurons expressing the similar vomeronasal receptor innervate multiple small glomeruli, which excite mitral cells and thus specific brain regions. (Each colour represents a population of vomeronasal sensory neurons, that express one different type of vomeronasal receptor. Adapted from [161].

Figure 2

Pheromone perception pathways from the main olfactory epithelium and vomeronasal organ, through the main and accessory olfactory systems, and thalamic and hypothalamic higher brain regions, ultimately leading to a hormonal and/or behavioural response. Stress pathway upregulation (green ↓) or suppression (green ⊥); aggression pathway upregulation (orange ↓) or suppression (orange ⊥). Adapted from [154].