Evaluating Responses by Sympatric Ungulates to Fence Modifications Across the Northern Great Plains

Across North America, incentive programs have assisted landholders with the construction of fences, often considered “wildlife friendly,” to assist in grazing management, which has resulted in a proliferation of fencing on the landscape. Many suggested “wildlife-friendly” fence modifications have not been evaluated for their effectiveness on the targeted species or evaluated to assess consequences for nontarget species. We evaluated the effects of 2 modifications aimed to increase fence visibility (sage-grouse [SAGR] reflectors and white polyvinyl chloride [PVC]) on the fence-crossing behavior of 3 sympatric ungulates in the Northern Great Plains. We used trail cameras from 2016 to 2018 to capture images of pronghorn (Antilocapra americana), mule deer (Odocoileus hemionus), and white-tailed deer (O. virginianus) at sites before and after fence sections were modified and compared crossing success by the 3 ungulates with that achieved at unchanged control sites. We used generalized linear modeling and a time-to-event approach to test the effect of fence modifications on ungulate crossing behavior. Our results showed that both SAGR reflectors and white PVC pipe did not impede fence-crossing behaviors for either pronghorn or deer, nor was there a time lag in use of sites observed after modifications were deployed. Though we did not alter the height of the bottom wire, there was enough variability in bottom wire height between sites that our results indicate a greater probability of successful crossing by all 3 ungulates as bottom wire height increased. We recommend implementation of both SAGR reflectors and white PVC pipe because our results demonstrate no substantial unintended consequences on the crossing behavior of pronghorn and deer.