Towards individual-based conservation strategies - the case of invasive raccoons in an agricultural pond-rich landscape.

Abstract

Raccoons have recently been declared alien species of special concern by the European Union. However, high densities in high-quality habitats such as wetlands make it almost impossible or at least extremely laborious to control raccoon populations with comprehensive and undifferentiated brute force approaches. Here, we asked if individual-based analysis may hint at more applicable conservation approaches that account for individual space use patterns. We used GPS collars to record the space use of 20 raccoons in their invasive range in northern Germany, a landscape dominated by intensive agriculture, including numerous small ponds. These ponds are biodiversity hotspots that act as source habitats and offer shelter and food for local wildlife, including vulnerable species like birds and amphibians. Half of the tracked raccoon individuals showed a weak preference for ponds as foraging grounds, yet the preference for larger waterbodies on the population scale masked this pattern. A detailed look at the intensity of pond use revealed that only a comparably small but highly mobile fraction of the local raccoon population used ponds intensively. These few individuals may thus have a disproportionate large negative effect on native wildlife, leading to a landscape-scale effect by disturbing the most vulnerable yet important habitat islands. Our results suggest that removing few specialized individuals might be an effective and economical strategy to reduce the impact of invasive species on local animal communities. Individual-based conservation and management strategies could be most effective in landscapes characterized by island-like biodiversity hotspots embedded in a low quality matrix.