Effects of temporary captivity on ranging behaviour in urban red foxes (Vulpes vulpes)

Abstract

Temporary removal of wild animals from a resident territory has the potential to markedly impact subsequent ranging behaviour, and may negatively affect post-release welfare and survival. Admission of sick or injured wildlife into temporary captivity (termed ‘rehabilitation’) is a common practice in the UK. However, post-release monitoring of rehabilitated animals is unusual or restricted to recording survival rates over limited time periods. As part of a wider study of urban fox behaviour, we employed an experimental approach to compare the ranging behaviour of seven rehabilitated and 13 wild-caught ‘control’ urban red foxes using GPS tracking. Foxes were tracked over a two-year period for an average of 48 nights, and seasonal and sex-related effects were controlled for via inclusion in statistical models. Three of the five movement parameters we investigated were irregular for the rehabilitated animals, relative to controls. These were: reduced likelihood of establishing a stable home range (42.9/57.1% of rehabilitated foxes versus 84.6% of controls); larger home ranges (Kruskal Wallis test, χ2=7.517, df=1, p<0.01); and further distance travelled from release point, as measured by overlap between initial and final home ranges (Linear regression, F1,12=4.755, df=1, P<0.05). Females moved greater distances than males overall, and foxes from both groups travelled further in spring, and delayed home range establishment in summer. However, these results were skewed by the movements of two apparently cooperatively breeding wild-caught vixens. Our data provide evidence of territorial displacement of rehabilitated foxes on release. We discuss the welfare implications of this finding.