Effect of mammalian mesopredator exclusion on vertebrate scavenging communities

Abstract

Carrion is a valuable resource used by facultative scavengers across the globe. Due to conflicts with humans, many vertebrate scavengers have experienced population declines due to direct persecution or indirect effects of human activities. However, little is known about the implications of altered scavenger community composition on the fate and efficiency of carrion removal within ecosystems. In particular, mammalian mesopredators are efficient scavengers that are often subjected to control, thus, it is important to understand how the reduction of this scavenger guild influences the fate of carrion resources and efficiency of carrion removal within ecosystems. We evaluated the influence of the absence of mammalian mesopredators on vertebrate scavenging dynamics by comparing the efficiency of carrion removal and species composition at carrion between sites where we experimentally manipulated mesopredator abundance and paired control sites. Overall scavenging rates were high, even within our mesopredator exclusion sites (79% of carcasses). Despite the exclusion of an entire guild of dominant scavengers, we saw little effect on scavenging dynamics due to the extensive acquisition of carrion by avian scavengers. However, we observed a slight reduction in vertebrate scavenging efficiency in sites where mesopredators were excluded. Our results suggest vertebrate communities are highly efficient at carrion removal, as we saw a functional response by avian scavengers to increased carrion availability. These data provide insights into the impact of mesopredator control on food web dynamics, and build upon the growing body of knowledge investigating the role of vertebrate scavengers on ecosystem services provided through carrion removal.

Effects on carrion consumption in a mammalian scavenger community when dominant species are excluded

“…4 Mean proportion and 95% confidence intervals of rabbit carcass consumption by the Egyptian mongoose in the exclusion and control areas (Cunningham et al 2018;Hill et al 2018). The inability of vultures to effectively utilize carrion in wooded areas probably means that they were unable to offset the reduction in carrion taken by the larger mammalian scavengers (Turner et al 2020). Therefore, our prediction 1 (that a decrease in scavenging efficiency increases the persistence time and proportion of carcasses not consumed) was supported, but not prediction 2 (that a significant increase would occur in the scavenging activity of the non-excluded mammalian facultative scavenger species).…”

Monitoring the dead as an ecosystem indicator

“…to reduce scavenging efficiency compared to an intact scavenger community and increase resources going to other scavengers (Turner et al, 2020).…”

“…These are related to scavenger use of carcasses and the time it takes for scavengers to locate carcasses. A slow rate of biomass loss might indicate that an ecosystem has lost a functional scavenger guild (e.g., Turner et al, 2020) or that there are excessive carrion biomass loads and scavengers are overwhelmed.…”

“…Scavenging rates can be assessed via a number of approaches including time to removal which is typical for smaller sized carcasses (e.g., Huijbers et al, 2015;Inger et al, 2016), or via monitoring carcasses using remote cameras that allows both monitoring of the scavengers themselves and the carcass (e.g., Cunningham et al, 2019). The exact contribution of different scavenger guilds to carcass removal can be assessed by simultaneously monitoring carcasses that are exposed to different scavenger exclusion scenarios (e.g., Bellan et al, 2013;Hill et al, 2018;Turner et al, 2020). Exact decomposition rates can be assessed by mass loss rates, measured visually or by weighing carcasses over time or at the end of an experiment.…”

Population modelling insights of extinct environments: the case of the Kem Kem palaeocommunity

“…The analysed system is a fragment of the potential palaeocommunity modules of that ecosystem, consisting of two top predators, Spinosaurus (S) and other Theropods (T ); "Fishes" (F ) that represent the community of fish species that are consumed by Spinosaurus; "Sauropods and others" that are items consumed by other Theropods. Carrion dynamics have an important role in extant ecosystems [17,18,19], and could also be important in the Kem Kem palaeoenvironment. Given that, I assume that the two top predators compete by resource competition for the Carrion (C), and may influence each other through a density-mediated interaction (DMI, hereinafter) regarding this consumption.…”