Wat eet een zwerfkat op Neeltje Jans? Inzicht in de aanwezigheid van kustbroedvogels en andere beschermde soorten in het dieet via morfologische en genetische analyse van kattenkeutels

The Province of Zeeland asked Wageningen Environmental Research to study the composition of the diet offeral cats living on the island Neeltje Jans, located in the Oosterscheldekering, one of the largerst Deltaworks along the Dutch coast. This island harbours valuable breeding colonies of various sea birds. We studied the cat’s diet by collecting scats during the bird breeding season of 2021 and identifying the prey composition based on two complementary methods: morphological identification and genetic identification by means of eDNA metabarcoding. The results showed that the diet mainly consists of voles and rabbits,although evidence of a total of 8 bird species was observed in the scats. In only one scat we observed DNA from one of the sea birds breeding on the island (a European herring gull or a Lesser black-backed gull), suggesting that the impact of the feral cats on Neeltje Jans on the local breeding colonies of these species is likely to be limited. A study of the population dynamics of these birds, including the role of cats in the totalpredation mortality, would help to further assess the risks.