Body Size, Defensive Behaviour, and Season Influence Mortality Probability in Wildlife Interactions with Electrified Fences

Abstract

Like many anthropogenic linear structures, fences are ubiquitous across South Africa and increasingly in the rest of Africa. Fences play a key role in conservation and livelihoods, including inter alia demarcating protected areas, safeguarding vulnerable populations of threatened species, and facilitating food security through the management of livestock and mitigating livestock predation from native predators. However, fences also have several deleterious effects, including curtailing historical animal migration routes, denying animals access to seasonally important resources, and providing a physical barrier on which animals can become entangled or electrocuted. Despite these negative effects being commonly known, few African studies have quantified the threat specifically posed by electrified fences, although several studies have highlighted the risks posed by unelectrified fences. This study investigated vertebrate interactions along 108 km of electrified fencing on a private game farm over nearly five years and analysed the effect of several predictive variables on the outcome of interactions with fencing. Overall, 43 vertebrate species were recorded interacting with the fencing on 782 occasions, resulting in 213 fatal interactions. Medium-sized mammals, specifically steenbok (Raphicerus campestris ) and Temminck's pangolin (Smutsia temminckii ), and large reptiles including rock monitor (Varanus albigularis ) and serrated tent tortoise (Psammobates oculifer ) were particularly prone to fatal interactions. Body size, season and defensive behaviour were the best predictors of a species' tendency for fatal interactions with electrified fencing. This study records several additional species that have not previously been recorded interacting with electrified fencing, and for the first time highlights the potentially large, albeit possibly local, negative effect that electrified fencing has on the rock monitor.