Mammal Rev . 2004, Volume 34, No. 4, 325–330. Printed in Great Britain. © 2004 Mammal Society, Mammal Review, 34, 325–330 Blackwell Science, LtdOxford, UKMAMMammal Review0305-1838Blackwell Publishing Ltd, 2004 ? 2004344325330Review ArticleReducing bait uptake in foxesM. Gentle, G. Massei and G. Saunders Correspondence: M. Gentle. E-mail: matthew.gentle@nrme.qld.gov.au Levamisole can reduce bait monopolization in wild red foxes Vulpes vulpes MATT GENTLE*†, GIOVANNA MASSEI‡ and GLEN SAUNDERS* *Vertebrate Pest Research Unit, NSW Department of Primary Industries, Forest Road Orange NSW 2800, Australia, †School of Biological Sciences, University of Sydney, Sydney NSW 2006, Australia, ‡Central Science Laboratory, Sand Hutton, York Y041 1LZ, UK ABSTRACT 1. Baits are used worldwide to deliver vaccines, contraceptives and poison to wild animal species. In carnivores, multiple bait uptake and bait monopolization by dominant individuals may reduce baiting effectiveness. This study investigated whether a conditioned-taste-aversion agent, levamisole, can be used to decrease bait consumption by individual wild foxes Vulpes vulpes. 2. The results indicated that after consuming levamisole-treated baits, foxes avoided eating treated baits but consumed untreated baits. We concluded that the reduction in bait con- sumption was achieved through learned aversion to levamisole rather than via conditioned- taste-aversion to baits. Adding levamisole to baits could potentially be used to reduce bait monopolization by individual wild foxes. Keywords: baiting, conditioned-taste-aversion, oral contraceptives, oral vaccines, repellency INTRODUCTION Following developments in research on orally administered vaccines and contraceptives as non-lethal wildlife management tools, baits are increasingly considered as useful delivery agents (e.g. Bradley et al., 1999; Masson et al., 1999). Foxes Vulpes vulpes in particular have been targeted using baits to deliver rabies vaccines, poisons and regulate fertility (e.g. Blancou et al., 1982; Marks, Nijk & Gigliotti, 1996; Farry et al., 1998; Bradley et al., 1999). Most of these studies have also stressed the need to improve the cost-effectiveness of baiting cam- paigns by targeting the maximum proportion of animals with the minimum number of baits. For foxes, multiple bait uptake, bait caching and monopolization by a few individuals have been quoted among those factors that may reduce the success of a baiting campaign (Trewhella et al., 1991; Saunders, Kay & McLeod, 1999). A method that could deter individ- ual foxes from eating more than one bait could therefore improve the cost-effectiveness of baiting campaigns. One approach that, in principle, is well suited to targeting individual animals and decreas- ing the likelihood of multiple bait uptake is the use of conditioned-taste-aversion (CTA). CTA occurs when an animal associates the taste of a food with illness and subsequently avoids consuming that food (Garcia, Hankins & Rusiniak, 1974). CTA can be experimentally induced by adding specific chemicals to food (Cowan, Reynolds & Gill, 2000). Recently, several compounds have been shown to induce CTA to a variety of foods in laboratory rats (Massei & Cowan, 2002; Massei, Lyon & Cowan, 2002). When tested on captive foxes, one of these compounds, levamisole hydrochloride, induced complete avoidance of the experi-