Landscape Heterogeneity and Woody Encroachment Decrease Mesocarnivore Scavenging in a Savanna Agroecosystem

Abstract

Increased agricultural intensification and extensive woody plant encroachment are having widespread effects on the functioning of grass-dominated systems at multiple spatial scales. Yet there is little understanding of how the provisioning of biodiversity-based ecosystem services might be altered by these ongoing changes. One fundamental ecosystem service that is decreasing globally, especially in human-altered landscapes, is scavenging that regulates disease processes, alters species distributions, and influences nutrient cycling. Accordingly, our goal was to understand how facultative scavenging, particularly that of mesocarnivores, was affected by landscape heterogeneity and woody encroachment in tropical-grassy savannas within an agricultural landscape mosaic. We baited (using chicken carcasses) plots across a gradient of land cover heterogeneity in areas with an open and closed canopy and subsequently measured scavenging rates. We found that scavenging efficiency of mesocarnivores and other small vertebrates was dependent on environmental variation at multiple spatial scales within our savanna agroecosystem. Mesocarnivores removed more bait when the overstory canopy at the plot (i.e., exact location of bait station) was more closed; in contrast, mesocarnivore scavenging was less efficient when patches (50 × 50 m area around the bait station) within the site had a higher density of shrubs. At the landscape scale, increased land cover fragmentation resulted in decreased amounts of scavenging by mesocarnivores. This study demonstrates that a relatively transformed agroecosystem can support the provision of important ecosystem services and offer an important buffer against loss of ecosystem services. Our results suggest that targeted woody encroachment control, protection of large trees, and management or mitigation of extreme levels of fragmentation can help maintain ecosystem service provision and biodiversity.