Barrier behaviour analysis (BaBA) reveals extensive effects of fencing on wide-ranging ungulates.
Abstract
As human activities expand globally, there is a growing need to identify and mitigate barriers to animal movements. Fencing is a pervasive human modification of the landscape that can impede the movements of wide-ranging animals. Previous research has largely focused on whether fences block movements altogether, but a more nuanced understanding of animals' behavioural responses to fences may be critical for examining the ecological consequences and prioritizing conservation interventions. We developed a spatial- and temporal-explicit approach, Barrier Behaviour Analysis (BaBA, available as an r package), to examine individual-level behaviours in response to linear barriers. BaBA classifies animal-barrier encounters into six behaviour categories: quick cross, average movement, bounce, back-and-forth, trace and trapped. We applied BaBA to wide-ranging female pronghorn Antilocapra americana and mule deer Odocoileus hemionus in an area of western Wyoming, USA, with >6,000 km of fencing. We found both species were extensively affected by fences, with nearly 40% of fence encounters altering their normal movements, though pronghorn were more strongly affected than mule deer. On average, an individual pronghorn encountered fences 250 times a year-twice the encounter rate of mule deer. Pronghorn were more likely to bounce away from fences, whereas deer engaged in more back-and-forth, trace and average movement near fences.We aggregated these behavioural responses to demonstrate how BaBA can be used to examine species-specific fencing permeability and to identify problematic fence segments in order to guide fence modification or removal.Synthesis and applications. Our work provides empirical evidence on how fences affect wildlife movement. Importantly, Barrier Behaviour Analysis (BaBA) can be applied to evaluate other linear features (such as roads, railways and pipelines) and habitat edges, enhancing our ability to understand and mitigate widespread barrier effects to animal movement.