Fox contact behaviour and rabies spread: a model for the estimation of contact probabilities between urban foxes at different population densities and its implications for rabies control in Britain.
A mathematical relationship between fox home range size and population density was derived from the literature and combined with behavioural data on movement patterns and encounters from urban Bristol, UK to formulate a predictive model of intergroup contact probabilities over a range of population densities. This contact probability-population density relationship was used to formulate a revised version of the rabies model which is used by the Ministry of Agriculture, Fisheries and Food as the basis of its rabies control policy for an outbreak of the disease in an urban area of Britain. The original and revised versions of the model were compared in terms of their predictions for the rate of rabies spread and their implications for rabies control in specific urban areas. It was concluded that an equivalent probability of successful rabies control is achieved by 5-15% lower fox control for the revised model compared with the original one. The greatest differences between the probability of successful rabies control for a given level of fox control under the 2 versions of the model occur in winter. The revised model predicted that the rate of rabies spread will be slower than predicted by the original model. This was attributed to the lower inter-group contact probabilities used in the revised model. Thus, there will be a greater chance of containment and elimination of the disease within a specified control area than was suggested by the original model. The heterogeneous nature of the urban landscape probably results in a lower frequency of contacts than would be observed between foxes living at the same densities in rural environments.