Flexible spatial organization of urban foxes, Vulpes vulpes, before and during an outbreak of sarcoptic mange

The social and spatial organization of urban fox groups prior to and during an outbreak of sarcoptic mange was compared with predictions derived from the resource dispersion hypothesis (RDH). We investigated the availability of three key resources. Neither daytime rest sites nor breeding sites appea red to be limited in availability. The availability of food deliberately su pplied by local householders was examined by questionnaire surveys. The dai ly and weekly amount of food supplied was greatly in excess of the minimum requirements of a pair of foxes, but was consistent between territories. Th e availability of this food source increased markedly as a result of more p eople feeding the foxes. In agreement with the RDH, group size prior to the outbreak of mange increased from 2.25 animals (N=4) to 6.57 animals (N=7). Before the outbreak of mange, two territories were divided. Increased scav enge availability on smaller territories may have promoted these changes. E xcluding these spatial changes, territories were very stable between years. After the outbreak of mange, group size declined as a direct result of man ge-induced mortality. Surviving animals increased their ranges only after n eighbouring groups had died out. Ranges did not increase in size in respons e to a decline in food availability. Nor were the increases in range size a ssociated with the relinquishment of parts of the existing territory. These postmange changes are contrary to the RDH. Three factors may have promoted these changes: the elimination of interstitial space, the forced dispersal of young or future division of the territory. (C) 2000 The Association for the Study of Animal Behaviour.