Canopy cover and forest management shape vertebrate scavenger assembly but not carrion removal rates

Abstract

Carrion decomposition is a key process in nutrient cycling and ecosystem functioning, driven by microorganisms, necrophagous insects, and vertebrate scavengers. The rate of decomposition is influenced by various factors, including environmental conditions, carcass characteristics, and scavenger assembly. In forests, canopy cover and structure shape microclimatic conditions and habitat features, yet little is known about how these characteristics affect carrion decomposition by vertebrate scavengers. As forest disturbances increasingly open up canopies, understanding the impact of canopy cover on carrion decomposition becomes essential. We investigated removal rates of small carrion at paired gap and closed-forest plots along a gradient of forest-management intensity in three regions in Germany, using camera traps to monitor vertebrate scavengers. Of 89 rat carcasses, 67 were removed by vertebrates. Initial removal rates were higher in gaps than in closed forests and at plots with higher forest-management intensity. However, over the full exposure time, removal rates were similar across all treatments. Differences in temporal patterns of carrion removal were linked to shifts in scavenger dominance, with red kite (Milvus milvus) prevalent in gaps and red fox (Vulpes vulpes) in closed forest. Our findings indicate that forest management and changes in canopy cover, such as those caused by disturbances, have little impact on carrion removal rates. Vertebrate scavenger assembly however differed between open and closed forests, which suggests functional redundancy among scavengers but that it is important that carrion resources are available for scavengers both in gaps and closed forests to promote overall biodiversity and maintain their ecosystem functions.