Reducing predation through conditioned taste aversion.

Abstract

Negative consequences arising from eating a particular food can result in subsequent avoidance of that food (e.g. Schaeffer, 1911). In the 1930s this process was identified as a constraint on the effectiveness of fast-acting rodenticides (Hamilton, 1936). Animals that become ill after consuming a sub-lethal dose of rodenticide bait learn to avoid that bait and become 'bait-shy' (Chitty, I954). This phenomenon underlies the domination of rodent control by anticoagulant rodenticides, since the I950s, because the 3-5 day delay between anticoagulant consumption and the onset of symptoms reduces the likelihood of an association being made (but see Smith et aI., I994). The association of the taste of a food with illness leading to reduced food consumption was recognized as a distinctive form of conditioned aversion by Garcia et al. (1955). Subsequently this has most commonly been described as conditioned taste aversion (CTA) although a confusing variety of other terminology has been used, including taste conditioned aversion, conditioned food aversion, conditioned flavour aversion and learned food aversion. The common elements of these are the pairing of taste as the conditional stimulus with illness as the negative unconditional stimulus, leading to subsequent aversion to food with the same taste. Conditioned aversion of this general form is widespread across taxa from molluscs to humans (Gustavson, 1977), and is one of the most intensively studied learning processes, with the laboratory rat (Rattus norvegicus) as the predominant subject (Riley & Tuck, 1985). It is widely believed that the CTA response has evolved to reduce the risk of poisoning and plays a leading role in determining dietary preferences (Rozin & Kalat, I97I; Kalat, I977). Aversive behaviour in general might be exploited to modify the feeding behaviour of species to meet wildlife management objectives. For instance, some feeding deterrents and repellents can create conditioned aversions (Rogers, I978; Avery & Decker, I994; Watkins et al., I994). It is important to recognize that, in these cases, the conditional stimulus is the taste of the repellent rather than that of the food to which it is applied. There is thus no expectation of reducing consumption of untreated food unless through association with food cues other than taste. A more ambitious aim is to generate an aversion to the taste of the food itself, thus leading to the protection of untreated food. The context in which this was first proposed was reducing coyote (Canis latrans) predation on live prey (Gustavson et al., I974). In this chapter we explore the possibilities of using this approach to reduce predation in conservation contexts.