Diets of native and introduced apex predators in Hawai'i

Abstract

We report here on the diets of four apex predators in Hawai‘i: the native pueo or Hawaiian short-eared owl (Asio flammeus sandwichensis) and three introduced species, the barn owl (Tyto alba pratincola), the feral cat (Felis catus) and the small Indian mongoose (Herpestes javanicus). To better understand dietary relationships between these predators, we studied diet, focusing on areas where they occur together. We collected disgorged owl pellets, and cat and mongoose faecal scats from eight areas located on five of the main Hawaiian Islands and identified prey items to the lowest possible taxonomic level. All species consumed rodents, birds, and arthropods, and the mammal species also included plants in their diets. The two owl species and the cat preyed primarily on rodents, whereas small cockroaches predominated in the diet of the mongoose. Diets of the owl species and the cat, but not the mongoose, varied significantly between areas. Dietary overlap was highest between the pueo and the barn owl and lowest between the owl species and the mongoose. Although barn owls took more rats than pueo, there was no evidence that the two owl species partitioned house mouse prey by size. On islands where there are no mongoose, both owls took a greater proportion of large arthropods in their diet, suggesting that mongoose reduced the abundance of the arthropod species that owls commonly took. There was no significant difference in pueo diets before and after introduction of the barn owl.