Scavenging Ecology

Carrion is a valuable nutrient resource in the environment that is used by a diversity of organisms encompassing all biological kingdoms. Due to the low cost of energy derived from carrion, most vertebrate species are facultative scavengers, and thus provide a critical ecosystem service for humans and other organisms by removing decaying animal matter from the environment. In fact, a surprising array of animals will forage on carrion, including eagles, white-tailed deer, and many species of snakes and lizards. However, despite the importance of scavenging for ecosystem health, many knowledge gaps still exist regarding the diversity and function of scavenger communities. In addition, while it is accepted that carcass size and location can influence the diversity and composition of scavenging communities, there is little research to support this assertion. In particular, scavenging research in human-disturbed landscapes is lacking as most studies have been conducted in relatively pristine environments with intact scavenger communities. Thus, there is a critical need to study scavengers in ecosystems that have been dramatically altered by anthropogenic land use.

Effects of urbanization on the efficiency and composition of vertebrate scavengers

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. To address this knowledge gap, we are using motion activated cameras to monitor experimentally placed fish carcasses in riparian zones of suburban and rural areas in northeast Georgia, USA. Our results thus far suggest fish carrion within riparian areas is readily consumed by terrestrial scavengers. However, carcasses are scavenged by vertebrates less often and persist longer in rural landscapes. These differences between landscapes appear to reflect the abundance of mesocarnivores (especially Virginia opossums), which are highly efficient scavengers, in suburban areas. Interestingly, our data also suggest nutrients from aquatic carcasses near water sources can readily move into terrestrial environments through scavenging, a finding we also reported in our research at the interface of aquatic and terrestrial ecosystems in Chernobyl.

Effects of carcass size, type (predator vs. herbivore), and habitat on scavenging dynamics

It is generally accepted that carcass size and location influence scavenging communities, yet there is little research supporting this notion. To date, most scavenging research has focused on a single carcass size or type and almost exclusively using lower trophic level carrion (i.e., herbivore), resulting in an oversimplified understanding of scavenging dynamics. Similarly, despite the fact that species composition often is greatly influenced by habitat and anthropogenic land use, few studies have taken a multi-habitat approach or incorporated human-impacted landscapes in scavenging studies. We are conducting a series of studies to fill these critical gaps by examining the influence of a large gradient in carcass size, carcass type (herbivore vs. carnivore), and a diversity of habitat types on the composition and efficiency of scavenging communities. Our findings thus far have revealed that all carrion is not created equal and that carcass size, type (herbivore vs. Carnivore), and habitat all interact to influence the species composition and efficiency of carrion use by vertebrates. This research continues to lead to new and interesting questions, and ultimately is helping to broaden our understanding of scavenging community dynamics and the flow of nutrients within food webs.

Effects of predator exclusion on the efficiency of scavenging communities

Intact scavenging communities provide numerous ecosystem services as they play a critical role in disease dynamics, nutrient cycling and redistribution, and carcass removal. However, the addition (e.g., invasive species) or removal (e.g., extirpation) of scavengers from ecosystems can disrupt the efficiency and composition of scavenging communities. This imbalance not only interrupts the flow of energy in an ecosystem, but also may lead to increased health risks for people, livestock, and other wildlife (e.g., disease). For instance, the recent dramatic decline of vultures in Asia has led to increases in feral dog and rat populations, resulting in a significant increase in human rabies cases from dog bites, as well as diminished efficiency of carcass removal by the scavenging community as a whole. We are conducting a series of studies to test the effects of the exclusion of entire guilds of predator communities on scavenging community dynamics, both through the experimental control of predators (via exclusion) and through investigation of scavenging dynamics in island ecosystems with highly disturbed vertebrate communities (Hawaii and Guam). These studies have revealed that scavenging communities are resilient to disruptions to the composition of species present within a system in terms of efficiency of carrion removal. However, invasive species are often highly efficient members of the scavenging community and thus in ecosystems where invasive species are present scavenging may provide important pathways for nutrient acquisition that further propagate the expansion of the numbers and distribution of these species.

Vulture spatial ecology and niche partitioning

Black and turkey vultures are scavengers commonly associated with areas of human development. Because vultures utilize anthropogenic resources frequently, they often face many hazards associated with human landscapes, such as collisions with airplanes, vehicles, wind turbines, and other structures (bird-strikes). The economic costs associated with bird-strikes are substantial and the problem is intensified with the fact populations of these species have been increasing in recent decades. However, the spatial ecology of many vulture species remains understudied. Further, despite high levels of dietary overlap and that black and turkey vultures often coexist in large numbers, the mechanisms that allow for the sympatric occurrence of these obligate scavengers are poorly understood. Using GPS/GSM transmitters, our lab studies the movement behavior and resource selection of black and turkey vultures, as well as the underlying habitat attributes that contribute to niche partitioning between these species.

Page updated

Report abuse