Data from: American black bears perceive the risks of crossing roads

Roadways may negatively impact wildlife species through vehicular-related mortality and spatial displacement or obstruction. Here we investigated physiological responses, which provide insights into the animal’s perception of its environment. We deployed GPS-collars in combination with cardiac biologgers on American black bears (Ursus americanus; 18 bear-years) in areas with differing road densities across Minnesota, USA. We tested whether bears exhibited acute stress responses, as defined by significant increases in heart rate (HR), associated with road crossings. Maximum HR between successive telemetry locations were, on average, 13 bpm higher when bears were known to cross a road. They crossed a road, on average, once per day. Different demographic groups (males, females with and without cubs) responded similarly. We found stronger HR responses when crossing high-traffic roads relative to low-traffic in half of the bear-year combinations we sampled. Bears crossed high-traffic roads mainly at night, but low traffic roads during daylight. Bear HRs first became elevated when 73−183 meters away from roadways. Our findings suggest that roadways act as an acute stressor, but the magnitude of the stress response appears to be mild. Elevated HRs may reflect an increased vigilance and recognition of threat when preparing to cross a road. Bears’ recognition and alertness to human-related threats is adaptive for living in human-altered landscapes.

道路可通过车辆碰撞致死、空间阻隔或位移限制，对野生动物种群造成负面影响。本研究旨在探究可反映动物对环境感知情况的生理响应。我们在美国明尼苏达州道路密度各异的区域，为美洲黑熊（Ursus americanus；共开展18个熊年的监测）佩戴了集成心脏生物记录仪（cardiac biologgers）的GPS项圈（GPS-collar）。我们测试了黑熊在穿越道路时，是否会出现以心率（heart rate, HR）显著升高为判定标准的急性应激响应。

连续遥测定位间的最大心率数据显示，当已知黑熊穿越道路时，其平均心率较基准高出13次/分钟（bpm）。黑熊平均每日会穿越道路一次。不同种群分组（雄性、带幼崽与不带幼崽的雌性黑熊）的应激响应模式并无显著差异。在我们采样的半数熊年监测组合中，相较于低流量道路，黑熊穿越高流量道路时的心率响应更为强烈。黑熊主要在夜间穿越高流量道路，而在日间穿越低流量道路。黑熊的心率会在距离道路73至183米时首次升高。

本研究结果表明，道路属于急性应激源，但应激响应的强度相对温和。心率升高可能反映了黑熊在准备穿越道路时，警惕性有所提升并识别到了潜在威胁。黑熊对人类相关威胁的识别与警觉性，是其在人类改造的景观中生存的适应性特征。