Effects of ungulate-proof fencing on space use by wild pigs

Abstract

Wild pigs (Sus scrofa) are a highly adaptable species that have invaded many regions and cause significant damage throughout the world. Ungulate-proof fencing is increasingly used in conjunction with other control techniques to manage wild pig populations. However, little is known about how fencing affects wild pig space use behaviors and whether any changes may be exploited to increase efficacy of control activities. Our goal was to understand how wild pigs altered their space use behaviors in response to newly constructed fencing. Specifically, we examined for changes in space use area (home range and core area), increases in overlap with conspecifics, and shifts in space use as ungulate exclusion fencing was constructed on northern Guam from February 2021 to March 2022. Wild pigs closer to the fence had decreased space use. For every 200 m nearer newly constructed fence, home ranges and core areas decreased approximately 15% and 16%, respectively. When individual wild pigs were enclosed by the fence, those animals increased their home range overlap with conspecifics by approximately 76% compared to wild pigs outside the fence. Wild pigs shifted their home ranges 3 to 9 times more during the first part of fence construction when 68% of the fence was completed compared to all other time periods, with male wild pigs shifting greater distances than females by 1.15 times. The construction of ungulate fencing led to smaller space use areas of wild pigs on both sides of the fence and intensified use of the area inside the fence by wild pigs contained within (i.e., more overlap). Management activities nearer the fence should account for decreases in home range and core area size to maximize population control efforts (i.e., more densely spaced trap sites). Enclosed wild pigs should be eradicated quickly to minimize damages to sensitive flora and fauna and decrease disease risk from intensified movement behaviors inside the fence.