Ecological factors driving the higher hedgehog (Erinaceus europeaus) density in an urban area compared to the adjacent rural area

Our objective was to explore the effect of natural food (earthworms and arthropods) and anthropogenic food (pet food) availability and the risk of predation by badgers on the density and recruitment of the European hedgehog in an urban area and the adjacent rural area located in northeastern France. Hedgehog density was estimated from distance sampling surveys applied to 43 line-transects visited monthly in 2006 and 2007. Hedgehogs were detected by using infrared binoculars. They were captured to be sexed, age-classified and marked. Earthworm, arthropod and pet food availability as well as distance to the nearest badger sett were assessed per transect through field sampling. Hedgehog population density, estimated from the detection of 127 hedgehogs, was 4.4 ± 1.3 individuals km−2 in the rural area and 36.5 ± 15.2 individuals km−2 in the urban area, where transects had lower arthropod biomass, higher pet food availability, and a greater distance from badger setts than in rural area. Adult hedgehog abundance was predicted by earthworm biomass and pet food availability. The number of young per adult female was predicted by arthropod biomass and distance to the nearest badger sett. The high urban hedgehog density did not seem to be mainly induced by an increase in reproductive rate and cannot be fully explained by food resource availability. The effect of variations in road kills and winter mortality factors between urban and rural area are discussed. We concluded that the combination of anthropogenic food and sheltered climatic conditions may provide good situations for hedgehogs and other hibernator species in urbanised environment.

► Hedgehog population density was 9-fold higher in the urban area than in the adjacent rural area of the North-eastern France field study.
► Adult hedgehog abundance per transect was predicted by both the main natural food (earthworms) and the main anthropogenic food (pet food) availability.
► Differences in earthworms and pet food availability between the urban and the rural area are not sufficient to fully explain the large difference in hedgehog density observed.
► Thus, the study does not fully support the general assumption that differences in food resource availability are responsible for the high density of urban adapter species.
► The effect of other potential factors driving this high density such as lower traffic kills and lower winter mortality due to sheltered climatic condition in cities is discussed.