Markers for measuring bait consumption by the European wild rabbit.

Poison baiting has proved to be a successful method for the control of European rabbits (Oryctolagus cuniculus) in some parts of the world, particularly Australia and New Zealand, and the possibility of developing a method appropriate for use in Britain is now being investigated. Distributing poisoned baits for rabbits is currently illegal in Britain, thus the potential effectiveness of the control method can only be assessed indirectly by laying unpoisoned bait and measuring the amount eaten per individual and the proportion of the population consuming bait. An essential preliminary to such measurements is the development of a bait-marking technique. Bait markers should satisfy the following criteria: (1) detection should be simple so that large numbers of animals can be examined rapidly; methods involving chemical analyses were consequently rejected (e.g., Larson et al. 1981); (2) their presence should not severely reduce bait palatibility; (3) they should not influence the health of animals that consume them; (4) they should persist in the animal for up to 8 days, which is the time taken before maximum bait consumption occurs (Rowley 1957); ideally a range of markers should be available that will allow changes in the pattern of bait consumption to be monitored over this period; and (5) they should enable estimation of the amounts of bait consumed.