This project will aim to identify and evaluate novel conditioned taste aversion (CTA) agents for use in reducing mammalian pest problems; such CTA agents should be environmentally safe and not detrimental to the target species in the long-term. The study will be composed of 4 specific objectives outlined as follows, together with ways in which they might be achieved: 1. Quantification of the ability of a minimum of 8 potential CTA compounds (fluvoxamine, paroxetine, tryptophan, ipecacuanha, monosodium glutamate, aspartic acid, prostaglandins, naloxone) to induce CTA. CTA activity of these compounds will be tested in Wistar rats and optimal doses (in terms of both safety and efficacy) will be determined for each compound. Additional safe, novel putative agents will be investigated, by examination of possible pathways and compounds (including hypoglycaemic agents, lipopolysaccharides, role of L-dopamine in nausea and appetite, and pharmaceutical compounds which have either failed clinical trials or have been withdrawn due to unacceptable nauseous side-effects); 2. Establishment of whether a short-term, weak CTA response can be transformed into a long-term, robust CTA response by reinforcement with a second exposure to the CTA agent. Longevity of the CTA responses in rats to cinnamamide and thiabendazole, which induce short-lived CTA following a single exposure, will be assessed following a second exposure; 3. Confirmation of the efficacy in CTA generation of compounds that induce a robust CTA response following delivery by oral intubation, when formulated for voluntary uptake in oral baits by a target species. Candidate compounds will be formulated to reduce detectability on ingestion (e.g. by encapsulation). CTA response will be tested in captive foxes and ferrets (Mustela putoria, used as a model for other mammals), using a no-choice protocol; and 4. Determination of efficacy of optimal compounds to reduce consumption of a familiar food by a free-living target species. A field location will be identified in which individuals of a potential target species are resident. Uptake of untreated bait (e.g. eggs, dog meat) will be monitored by remote video, before and after consumption of bait treated with the candidate compound. The possibility of replicate and control trials at other field sites will also be explored.