An Analysis of Some of the Factors Affecting Dispersal in an Urban Fox (Vulpes vulpes) Population

Abstract

(1) Capture-mark-recapture data were obtained from 1387 foxes (710 males, 677 females) tagged in and around the city of Bristol. These results were combined with a variety of demographic data describing the fox population to examine the dispersal behaviour of urban foxes. (2) Dispersal was protracted, but occurred principally amongst sub-adults; by the end of their second year, 72.7% of male cubs and 32.3% of female cubs had dispersed. Of animals first caught as adults, only 35.3% of males and 29.2% of females dispersed. Mean recovery distances were small, although occasional movements up to 18 km were recorded. (3) For males, mean age of recovery dead was significantly higher for non-dispersed than for dispersed animals. For both males and females, dispersed animals born near the city centre lived significantly longer than those born closer to the periphery of the city. In the population as a whole, there was no evidence of animals dispersing in a particular direction, but littermates were more likely to disperse in the same general direction. The effects of population density at the capture and recapture points on dispersal are described. (4) A discriminant analysis was used to compare dispersing and non-dispersing foxes, using five predictor variables. For males, small cubs from large litters were more likely to disperse. For females, those that dispersed came from large litters. Using a discriminant analysis and six predicator variables to compare foxes that dispersed further than or less than the mean distance, males that moved further were significantly smaller and born in areas of lower fox density, usually closer to the periphery of the city. (5) These results are discussed in relation to the costs and benefits of dispersal for a subadult fox.