‘Reserve effect’: An opportunity to mitigate human-wild boar conflicts

Wild boar growth in numbers and range is associated with increasing economic and environmental impact. Hunting has been traditionally used to reduce wild boar numbers. Areas where hunting is not allowed may attract wild boar from neighbouring hunting grounds. This phenomenon is called 'reserve effect' and could cause temporarily localised, high densities of wild boar in areas where hunting is banned. To investigate the occurrence of 'reserve effect', this study was conducted in two natural reserves of 400 and 250 ha inside the Montseny Natural Park, Catalonia, Spain where regular hunting of wild boar is not permitted, and only sporadic driven hunts/year are authorised for population control. The aims of the study were to evaluate if wild boar use these reserves as a refuge when hunting is carried out in the surrounding areas and to assess the effects that occasional drive hunts inside these reserves may have on wild boar numbers and social organization. From 2012 to 2015 camera traps were placed in the two reserves without using any bait. Cameras operated for 1.759 days, including hunting and non-hunting seasons, and 37.574 wild boar images were obtained. A 'reserve effect' was detected, as following hunting in the surroundings grounds, the number of wild boar increases inside reserves. Occasional driven hunts conducted in the reserves are effective in reducing the number of individuals and the effects persist for at least 45 days. Hunting disrupts wild boar social organization, as group size was significantly reduced. These results suggested that targeting refuge areas, once hunting in the surroundings causes wild boar to concentrate in these areas, is effective for population control. These findings could also be used to design trategies to optimise population control and offer opportunities for disease management such as vaccination, or to facilitate eradication in areas affected by disease outbreaks.