A comparative assessment of potential conditioned taste aversion agents for vertebrate management.

A conditioned taste aversion (CTA) is acquired through an association between the taste of a food and a feeling of illness experienced after ingestion. It can be induced deliberately by the addition of an undetectable illness-inducing chemical to food. Harnessing the CTA response could provide humane and effective means of controlling vertebrate pest problems. For field use, the ideal illness-inducing chemical should induce a robust CTA after a single oral dose, at which it must cause neither chronic illness nor persistent detrimental effects in the target or any non-target species at risk of exposure; it must also be undetectable and physically stable in the bait substrate. At present, no compound that satisfactorily meets all of these criteria has been identified. 17alpha ethinyl oestradiol meets most but, as a synthetic oestrogenic hormone, it can affect reproductive processes. The ability of two potentially safe compounds, cinnamamide (160 mg/kg) and thiabendazole (100 and 200 mg/kg) to generate a CTA in the laboratory rat Rattus norvegicus11 post-treatment tests (6 months). Thiabendazole at 200 mg/kg induced the next best CTA, persisting for five post-treatment tests. Cinnamamide and thiabendazole could provide safe alternative CTA agents to 17alpha ethinyl oestradiol for field use; the use of a second dose of these compounds to improve longevity of the CTA warrants further study.