Optimum group size for defending heterogenous distributions of resources: A model applied to red foxes, Vulpes vulpes, in Oxford city

Under some circumstances, group territoriality is thought to be explained by patterns of resource availability, if the smallest economically defensible territory for a minimum social unit (breeding pair) can also sustain additional animals. Red foxes (Vulpes vulpes) are typically solitary carnivores, breeding in pairs, but in urban and suburban areas of Oxford city they live in groups of three to five adults while foraging largely independently. Previous attempts to explain their social behaviour have considered variations in resource availability with time; consideration of spatial heterogeneity alone, however, suggests a simpler explanation in terms of defence costs. We show how group-living can result from competing neighbours maximizing resource acquisition and minimizing defence costs within an environment of fine-scale resource heterogeneity. © 1992 Academic Press Limited.