Human impact overrides bioclimatic drivers of red fox home range size globally

Diversity and Distributions published by John Wiley & Sons Ltd Aim: Identifying the variables that influence animal home range size is important for understanding the biological requirements of individuals and their social interactions. Given their often broad distributions, carnivores are model organisms for studying range-wide determinants of home range size. Here, we test predictions about environmental determinants of home range size for one of the world's most widely distributed carnivores, the red fox (Vulpes vulpes). Location: Global. Methods: We compiled a database of 70 mean home range estimates from 62 studies and four continents, which we analysed according to site-based temperature, precipitation, environmental productivity and human influence variables. Results: We found a very strong negative effect of the Human Footprint Index (HFI), with fox home range size decreasing as the level of human impact increased. When analysing the constituent components of the HFI separately, we found that human population density was the only well-supported variable (cf. built environments, croplands, pasture lands, nightlights, railways, roads and navigable waterways). Predicted home range size at the highest human population densities (0.75 km2) was 93% lower than at the lowest population densities (10.83 km2). We also found that home range size increased as mean annual temperature and temperature seasonality increased. The analyses did not support our prediction that home ranges would be smaller in areas of higher environmental productivity or precipitation. Main conclusions: Smaller home range sizes observed in highly disturbed areas can be attributed to increased food availability from anthropogenic sources. The lack of an effect of environmental productivity contrasts with previous studies that have shown a negative relationship with carnivore home range size. It may be that anthropogenic food sources have negated the impacts that low-productivity environments have on fox home ranges. Our results emphasize the strong potential for human activities to transform animal space use across the globe.