A follow-up assessment of wildlife-permeable fences used in the reintroduction of bison

Fences are an important tool for anchoring reintroduced species to a target area, and there is a need to understand their effect on other wildlife species. However, little is understood about the response of wildlife to newly constructed fences over time. We evaluated fences used in the reintroduction of plains bison Bison bison to Banff National Park, Canada. These fences were designed to contain reintroduced bison while allowing for the free passage of other wildlife. In 2020, we provided an assessment of the permeability of several fence designs. Here, we investigated longer-term fence effects and addressed the emerging question of whether wildlife adapt their behaviours to navigate fences more effectively over time. We used an expanded array of remote cameras and a before-after-control-impact design to evaluate changes in detection probability for 12 species. Next, we tested for changes in crossing rates and travel speeds of migratory elk Cervus canadensis using 22 years of GPS collar data. Finally, we examined whether species detections or elk movements changed over time after fences were constructed. Changes in detection probability near fences were inconsistent between species. Elk fence crossing rates decreased after fence construction, and travel speeds slowed by a negligible amount. However, these effects were temporary - wildlife learned to cross fences more efficiently over time. Elk movement metrics followed a non-linear pattern after the appearance of fences and began returning to pre-fence states after approximately two years. Our study provides new information on the implementation of fences for conservation objectives while minimizing impacts on sympatric wildlife.