Foraging behaviour in ecotoxicology: tool or endpoint? (BERISP)

Biology, Universiteit Antwerpen, Antwerpen, Belgium; N. Van den brink, H. Baveco, Alterra, Wageningen, Netherlands. The health of residential wildlife is increasingly threatened by the accumulation of heavy metals through terrestrial food chains. An important determinant of contaminant uptake is the foraging behaviour. Nevertheless, it is rarely included in ecotoxicological risk assessments and often subject to unrealistic assumptions. In our study bioaccumulation of heavy metals was monitored in a three-step terrestrial food chain, and foraging behaviour of the predator was assessed using highly quantitative GPS mapping. As a model system we chose the soil – earthworm/ beetle – hedgehog food chain in two residential park areas in the region of Antwerp (Belgium). These parks are situated along a metal pollution gradient. Metal concentrations of prey items and soil were assessed in different habitat types. Cadmium and lead concentrations were significantly habitat dependent. For cadmium the difference between habitat types were consistent throughout the food chain. In contrast, lead concentrations in soil were higher in forest than in grassland, whereas the opposite was observed for hedgehogs. This was due the spatial heterogeneity in the abundance of earthworms which were about 300 times more contaminated with lead compared to beetles. Our observations clearly demonstrate that knowledge of foraging behaviour and prey identity and prey availability is indispensable for an accurate appraisal of the risk of soil pollution for resident wildlife. It remains to be explored to which extent the foraging behaviour is determined by the microspatial variation in pollutant concentrations, and as such it might be rather an endpoint in stead of a tool in ecotoxicology.