Carcasses of invasive species are predominantly utilized by invasive scavengers in an island ecosystem

Invasive species have significantly affected ecosystems, particularly islands, and species invasions continue with increasing globalization. Largely unstudied, the influence of invasive species on island ecosystem functions, especially scavenging and decomposition, could be substantive. Quantifying carcass utilization by different scavengers and shifts in community dynamics in the presence of invasive animals is of particular interest for understanding impacts on nutrient recycling. Invasive species could benefit greatly from carcass resources within highly invaded island ecosystems, through increased invasion success and population growth, subsequently exacerbating their impacts on native species. We quantified how experimentally placed invasive amphibian, reptile, small mammal, and bird carcasses were utilized by vertebrate and invertebrate scavengers on the Big Island of Hawai'i in three island habitats: a barren lava field, a vegetated lava field, and a rainforest. We used camera traps to record vertebrate scavengers removing carcasses and elapsed time until removal. We evaluated differences in scavenging between vertebrates and invertebrates and within the vertebrate community across different habitats and carcass types. Despite the small carcass sizes (<1 kg) used in this study, 55% of carcasses were removed by vertebrate scavengers, all invasive: mongoose, rodents, cats, pigs, and a common myna. Our data indicate that invasive vertebrate scavengers in this island ecosystem are highly efficient at assimilating a range of carrion resources across a variety of habitats. Carcasses of invasive animals could contribute substantially to energy budgets of other invasive vertebrate species. This may be a critical component contributing to successful invasions especially on islands and subsequent impacts on ecosystem function.