The potential for exploiting conditioned taste aversion (CTA) in wildlife management.

Abstract

Conditioned taste aversions (CTAs) are a well-researched aspect of animal behaviour adapting an individual's innate food preferences to its specific environment. The evident power of CTA to cause lasting avoidance of referent food types even in the absence of alternative food is impressive. The fact that CTA towards a harmless referent food can be contrived by the addition of a toxin at low concentration has led wildlife biologists since the early 1970s to speculate that CTA might be exploited to curtail unwanted predation.
The history of research into wildlife related applications of CTA has been controversial, owing much to scientific and political fashions, and in several cases to poor experimental design. The best of the literature demonstrates unambiguously that the exploitation of artificial food sources by free-living wild predators can be manipulated through CTA. Unresolved questions include whether CTA towards dead specimens of a referent species will prevent a predator from killing that species.
The CTA approach addresses individual predators whereas other methods of predation management (culling, exclosure, fertility control) clearly address much larger populations. Since many predator species are territorial and actively repel intruders, targeting the behaviour of individual territory-holding predators promises economy of effort.
Although a large number of chemicals have been identified as having aversive properties, selection of suitable ones for potential wildlife management applications is problematical. To produce CTA there are only 2 fundamental requirements: (1) an adequate margin between aversive and acutely toxic doses, and (2) undetectability in referent food at the necessary concentration. For practical use, consideration of side-effects on target wildlife, aversive and side-effects on non-target wildlife, human safety and environmental contamination considerably restrict selection. At the most optimistic assessment, CTA applications would be a small market for chemical manufacturers, therefore wildlife applications are unlikely to be a high research priority.
Field methodology to exploit CTA must overcome a large number of practical difficulties requiring detailed study to resolve; these are not techniques that can be developed through practice. The likely interaction between CTA applications and existing, mainly lethal, predation management strategies is discussed.