Bait Consumption by the European Rabbit in Southern England

Abstract

The consumption of nontoxic, sliced carrot baits by 10 free-living European rabbit (Oryctolagus cuniculus) populations was investigated using Rhodamine B dye and fluorescent acetate floss fibers as bait markers. Total bait consumption was highest after 5-8 days of exposure. Increases in consumption between the 3rd and 8th days resulted from bait consumption by greater numbers of rabbits rather than increases in the amounts eaten by individuals. The data suggest that the more widely ranging individuals began consuming bait earlier than others. The average daily bait consumption/individual after 8 days of exposure varied between 216 and 346 g/kg body weight. The proportion of individuals eating bait was inversely related to the distance of their burrows from bait. There were no significant differences (P > 0.05) between sexes or among age classes in the proportions of animals consuming bait. Males ate significantly more (P < 0.001) bait than females. Adults ate significantly less (P < 0.05) bait than animals <9 months of age. It is concluded that sliced carrot bait could be used effectively as a vehicle for toxicants to control rabbit populations in Britain, provided that its presence does not substantially reduce bait consumption. A toxicant concentration considerably lower than that employed in Australia and New Zealand could be used because of the large amounts eaten by individual rabbits, thereby substantially reducing the risk to nontarget wildlife. J. WILDL. MANAGE. 51(2):386-392 The European rabbit is a major pest of agriculture in Great Britain. This problem is likely to increase as the effects of myxomatosis on rabbit numbers wane and improved methods of rabbit management become necessary (Ross and Sanders 1984). Toxicants have been successfully used to control rabbits in both Australia and New Zealand (Oliver et al. 1982 a,b). However, distributing toxic baits for rabbits is currently illegal in Britain. The study reported here forms part of an investigation into a baiting method that would be acceptable in Britain if a suitable toxicant (humane, low risk to nontarget species, and efficaceous) was available. The rabbit is a grazing animal and consumes large quantities of food relative to its body size. This suggests that low concentrations of toxin could be used effectively (if its presence does not constrain bait acceptance), hence reducing the risk to many nontarget species that would be unable to consume sufficient bait to receive a lethal dose. In these circumstances an effective baiting technique must involve consumption of large amounts of bait by a high proportion of a given rabbit population. Changes in these parameters with increasing length of exposure to nontoxic, sliced carrot bait, equivalent to a period of prebaiting prior to the use of toxin, have been investigated using 2 bait markers, Rhodamine B dye and fluorescent acetate floss fibers (Cowan et al. 1984). In addition, variations in patterns of bait consumption have been considered in relation to age, sex, and the distance of rabbit warrens (interconnected burrow systems with multiple entrances) from bait points. We thank landowners, C. A. Swan, T. Steele, L. M. Lelliott, G. Lambourne; and other Minist. Agric., Fish., and Food staff for access to the study sites and assistance in the field and laboratory; J. Bell for valuable discussion on the use of bait markers; A. Hart for statistical advice; and W. A. Rees and J. Ross for constructive criticism of earlier drafts of this paper.