Diet of raccoon dogs (Nyctereutes procyonoides) in Danish wetlands with focus on ground-nesting birds and amphibians

In European countries, raccoon dogs (Nyctereutes procyonoides) are believed to impact ecosystems and potentially threaten native species. In this study, the stomachs of 525 raccoon dogs culled in Danish wetlands were analysed and compared to 53 stomachs of adult raccoon dogs killed by vehicles, from the countryside. The stomach content was analysed using traditional macroscopic technics supplemented by eDNA analysis. The diet of raccoon dogs in wetlands did not differ notably from that of raccoon dogs in other parts of Denmark except for the larger amount of bait, and less shrews and fruit. More than 80% of the diet of adult raccoon dogs in wetlands consisted of bait, birds (mainly ducks taken in autumn and songbirds), amphibians, carrion, berries, fruit, and grass. Also, insects (mainly larger beetles and aquatic insects) occurred in the diet of raccoon dogs in wetlands. Waterfowl eaten during the autumn and winter are likely to be migrating birds. A high number of carrion beetles and fly maggots indicates a high consumption of carrion of all kinds. Eggs of ground-nesting birds made up a negligible part of the raccoon dog's diet. eDNA-analysis found no trace of shorebirds and only common species of amphibians were recorded. This study provides no evidence that raccoon dogs are a threat to ground-nesting birds nor to endangered amphibians in Danish wetlands.