Feeding habits of house and feral cats (Felis catus) on small Adriatic islands (Croatia)

The domestic cat (Felis catus), a globally recognised invasive predator, was introduced to the Adriatic islands (Croatia), but its feeding ecology and impacts on biodiversity in this region is unknown. We studied the feeding habits of house cats living in villages and feral cats on the outskirts of villages on two small islands (Olib and Silba) by analysing faecal samples collected in the spring and autumn periods. Our hypothesis was that the feeding strategies of cats as top mammalian predators vary in different environments, due to significant dissimilarities in their food resources. We surveyed the abundance of cats and their primary food types, e.g. small mammals, birds, rabbits Oryctolagus cuniculus, and lizards. Our results suggest that house cats fed most often on birds and common household food, while feral cats ate mostly small mammals and lizards. Feral cats preferred the invasive mesopredator black rat (Rattus rattus) (Ivlev's index of preference, feral cats E-i = 0.72, house cats E-i = 0.14), suggesting that cats might have an effect on rat populations. Common rabbits had a low density and were preyed on only occasionally. In both cat groups, predation on birds was more frequent during autumn migration when bird abundance was higher than in the spring breeding period. Both groups were food generalists but in different ways, which is a fact that should be considered in planning predator pest control on the islands.