A Changing Landscape of Fear within Gorongosa National Park: Differential Restfulness of Bushbuck (Tragelaphus sylvaticus) Before and After Carnivore Reintroduction

Abstract

Top carnivores impact prey species through extensive risk effects, beyond lethal predation, that reduce prey fitness even without direct interaction. Costs such as reduced foraging to compensate for increased vigilance, or exclusion from otherwise high-quality habitat due to risk, demonstrate the wide-reaching effects relatively low numbers of carnivores can have on large prey populations. As conservationists weigh possible methods of restoring degraded landscapes, including “rewilding” or reintroducing apex predators, it is important to know what kinds of responses that may elicit in existing prey populations. By taking advantage of the unique absence of large carnivores within Gorongosa National Park (GNP) in Mozambique—and the recent reintroduction of predatory African wild dogs (Lycaon pictus)—we were able to conduct research into the plasticity of antipredator behavior and concept of a “landscape of fearlessness.” In 2015, some of the park’s bushbuck (Tragelaphus sylvaticus) were found to have expanded beyond their natural woodland habitat into the more exposed floodplain area, which is at odds with the species’ typical secretive behavior. It was hypothesized, and supported by experimental research in 2016, that some bushbuck likely moved to the floodplain in response to reduced predation risk following several decades of carnivore absence. If and how those bushbuck would react to the reintroduction of predators, and whether that would result in a reinstatement of a landscape of fear, remained largely unexplored. This study aims to expand upon previous research by examining the effect of predator reintroduction on bushbuck restfulness, which serves as a more easily identifiable inverse measure of vigilance. By analyzing several years’ worth of camera trap footage, we were able to compare prey restfulness and other behavior before and after the reintroduction of wild dogs. We also looked at behavioral differences between bushbuck residing in the floodplain versus woodland areas to examine the effect of habitat on antipredator responses. We found that both carnivore reintroduction status and habitat are, among other included variables, factors which significantly influence bushbuck behavior. As might be expected, the renewed presence of wild dogs, in particular, seems to be highly associated with decreased bushbuck restfulness.