White-Tailed Deer Baiting Altered Black Bear Site Use but Not Movements or Range Size

Intentional anthropogenic food subsidies (i.e., baiting and supplemental feeding) can have profound individual-level effects on wildlife. We assessed the influence of bait sites targeting white-tailed deer (Odocoileus virginianus) on nontarget American black bears (Ursus americanus) in Michigan's Upper Peninsula, USA. We used black bear GPS collar data collected during July-August 2013-2019 to assess differences in recursive site use metrics (i.e., number, duration, and time between visits) and movement metrics (i.e., range size, step length, and turning angle) using a before-after control-impact design. We compared site use at 116 baited and 81 unbaited control sites before (pretreatment) and after (treatment) bait applications. We compared movements between 32 GPS-monitored bear-years (i.e., individual bears monitored during July-August of each calendar year) where bait was within the bear's home range and eight bear-years where bait applications occurred outside individuals' home ranges. Bears exhibited 3 times more visits and 11 times longer durations of use at active bait sites during the treatment period than unbaited and pretreatment controls. Active bait site visits were also more nocturnal during the treatment period than visits to unbaited and pretreatment control sites. Movement metrics did not, however, differ between bears with and without bait in their home ranges regardless of treatment period. Our results support the known adaptability of black bears to anthropogenic food subsidies but indicate use of this resource did not influence larger-scale movement patterns. Our work furthers understanding of black bear behavior by explicitly identifying greater use of baited versus unbaited sites without alteration of movement metrics.