Uptake of Baits by Red Foxes (Vulpes vulpes): Implications for Rabies Contingency Planning in Australia

Abstract

Baits containing the bait marker iophenoxic acid were used to quantify bait uptake by red foxes in a rural environment in north-eastern New South Wales. Baits were distributed at a mean density of 4·4 baits km-2. Serum iodine levels were analysed from a sample of 29 foxes shot on two baited sites and a nil-treatment site. The mean percentage of foxes with elevated seral iodine, indicating the consumption of at least one bait, was 58·3%. This rate of bait uptake would not consistently deliver reductions in fox densities or immunisation levels considered necessary for the control of rabies enzootics in Europe and North America. The minimum number known to be alive (MNA) method overestimated population reduction and underestimated abundance. Indirect estimators of population abundance, such as bait-station indices, are of more use in rabies contingency planning and modelling. This is because they are more reliable, are likely to overestimate abundance, and are more precautionary. Shooting of foxes at night was an inefficient method of reducing fox populations.