Ecological Factors Driving Uptake of Anticoagulant Rodenticides in Predators

Abstract

In recent years anticoagulant rodenticides have emerged as an important factor reducing the survival of many birds of prey and some predatory mammals. Understanding the ecological factors driving the exposure of predators is a key component in assessing the risk posed by anticoagulant rodenticides. We have reviewed the literature to better understand and synthesize the ecological factors driving AR exposure in predators, focusing on landscape and environmental management, traits of the exposed predators and the most common exposure pathways. On a global scale, the large input of ARs into urban and agricultural settings, and the relatively large footprint of these landscapes, has led to widespread AR exposure of many species, ranging from insects to large carnivores. General inferences can be made with regards to the traits of the most affected species. We determined that at-risk predators tend to be nocturnal opportunistic species for which rodents are a key dietary component, seasonally or year-round. They also tend to be non-migratory and occupy habitats within, or in close proximity to landscapes that are heavily influenced by human activities such as intensive agriculture or urban areas. Predators that consume rats in urban environments are disproportionately affected by ARs. As our understanding of how ARs are transferred up the food-chain is still limited, there is a need to further comprehend the extent to which non-target prey are being exposed to ARs in different landscapes, as we are frequently documenting AR residues in predators that do not typically prey on rodents. We recommend a focus on urban landscapes, where to date no exposure data has been collected on non-target prey. We also have a very limited understanding of non-target prey exposure in the urban-wildland/agricultural interface where opportunistic predators are known to hunt both habitat types interchangeably. Finally, we need to decipher whether the mounting evidence of exposure in predators translates into any population level effects.