Learning and Applications of Chemical Signals in Vertebrates for Human–Wildlife Conflict Mitigation

Abstract

Human–wildlife conflict (HWC) is a pervasive, global conservation issue that occurs whenever interactions between people and wildlife result in a negative outcome for either or both parties or the resources upon which they rely. Humans are impacted by wildlife either directly through their survival or health, or indirectly through damage to their food resources or property. Alleviating HWC has relied upon means from the individual to the population scale. Problem animals can be killed, relocated, or trained to avoid human habitations. Animal populations can be reduced through lethal or non-lethal means. Lethal control or relocation often have consequences such as biodiversity loss, unforeseen trophic cascades, and other ecologically detrimental effects. In many cases, the preference may be to keep the animals in question in the region but to reduce their impact on humans. In such situations, barriers can be constructed but these also have potential negative ramifications for other species as well as high costs for construction and maintenance. For invertebrate pests, a push–pull integrated pest management strategy has become increasingly popular. Chemical signals in the form of a natural repellents and attractants serve to keep pests away from crops and attract them to other areas, often traps. For vertebrates, the lack of known chemical signals hampers this approach and furthermore, the lethal trapping of individuals often is undesired. However, biological fences in concert with training animals to avoid the conflict area (e.g., crop or livestock) have potential for reducing HCW, especially for longer-lived, medium- to large-sized vertebrates. In lieu of using natural signals with known function, the proposition is to invoke a novel odor that would be unusual in the range of the problem species. Such an odor would be associated with strongly aversive stimuli near points of conflict and used as a warning of such a stimulus for future encounters. This novel scent fence would elicit anxiety and arouse a memory of discomfort and fear in the animal, motivating it to move away from the area without another interaction with the aversive stimulus. The odor would create an atmosphere of unease and avoidance rather than be the repellent itself. This approach provides further impetus for understanding better the chemical communication and the specific chemical signals used by vertebrates. In advance of those discoveries, odors may be useful as part of an aversive conditioning program to alter movement patterns of animals and keep them away from crops and livestock.