Effects of urbanization on the efficiency and composition of vertebrate scavengers

Abstract

As human populations continue to expand, urbanization will increase and impact ecosystem processes, contribute to habitat fragmentation, and alter community composition of species. While some species can adapt to the rapidly changing environment, urbanization can favor generalist species and reshape food webs, which may result in ecological instability. Determining how wildlife respond to urbanization is necessary for management and city planning purposes in order to create suburban areas where humans and wildlife can coexist. One area that needs more focus is the effects of suburbanization on scavenging species, and how land development can alter scavenging dynamics and the redistribution of carrion-derived nutrients within food webs. We used motion activated cameras to monitor experimentally placed fish carcasses in riparian zones of suburban and rural areas in northeast Georgia, USA. We conducted 300 trials across both landscapes that were scavenged by 7 mammalian, 2 avian, and 2 reptilian species. Our results revealed fish carrion within riparian areas was readily consumed by terrestrial scavengers. However, carcass fate (whether the carcass was scavenged or not) and carcass persistence differed between suburban and rural landscapes. Carcasses were scavenged by vertebrates less often and persisted longer in rural landscapes. Species richness was similar and mesocarnivores were the predominant scavengers in both landscapes. However, scavenging by the Virginia opossum (Didelphis virginiana) was more prevalent in the suburban landscape relative to the rural landscape (61% and 36% of scavenging events, respectively). While raccoons (Procyon lotor) scavenged carcasses fairly equally across both landscapes, the American black bear (Ursus americanus) and red-shouldered hawk (Buteo lineatus) scavenged more frequently in rural areas. Our data suggest that suburban species, especially opossums, may be highly adapted to foraging in an anthropogenic environment. Additionally, nutrients from aquatic carcasses near water sources can readily move into terrestrial environments through scavenging. These results contribute to the growing body of scavenging ecology and the effects of urbanization on wildlife.