BEHAVIORAL-RESPONSES TO FOOD ADDITION BY HEDGEHOGS

We conducted a field experiment at a 4-ha sports ground in Oxford between May and August 1992 to analyse the role of learning and social organization in the short-term responses of hedgehogs Erinaceus europaeus to manipulations of food availability. On six nights we uniformly distributed 36 'prey' (cat food chunks) twice a night in an 70 x 70 m area (the 'patch'). Prey were placed at sites marked with small flags. In a subsequent experiment lasting five nights, non-marked and randomly distributed prey were provided. We regularly mapped the position of individuals, before, during and after both food supplementation treatments. Hedgehogs showed a stable pattern of spatial utilisation of the habitat during the non-hibernation months prior to experimental perturbation. Addition of food to parts of the habitat significantly and rapidly changed these patterns. a) Hedgehog density increased in food supplemented parts of the habitat. b) Hedgehogs learned to associate visual cues with the presence of food. c) Hedgehogs learned the spatial location of patches. d) Hedgehogs probably engaged in 'area restricted' searching. Hedgehogs had overlapping home ranges but showed a uniform distribution within patches and avoided conspecifics at distance <30 m. The number of different individuals visiting the area decreased throughout the experiment. Food addition did not significantly change the mean density of hedgehogs, perhaps because social interactions placed an upper limit on density in the areas with supplementary food.