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.

道路可通过车辆致死、空间位移或栖息地阻隔对野生动物种群造成负面影响。本研究聚焦于生理响应，这类响应可揭示动物对所处环境的感知状态。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；18熊年）佩戴了集成心脏生物记录仪（cardiac biologgers）的GPS项圈（GPS-collars）。我们检验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反应。在连续遥测定位点间测得的最大心率，在已知黑熊完成道路穿越的情况下，平均升高13次/分钟。黑熊平均每日穿越道路一次。不同种群分组（雄性、带幼崽雌性与无幼崽雌性）的应激响应模式相似。在我们采样的半数熊年组合中，相较于低流量道路，黑熊穿越高流量道路时的心率升高幅度更为显著。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。黑熊的心率在距离道路73−183米时即开始升高。本研究结果表明，道路可作为急性应激源，但应激反应的强度相对温和。心率升高或反映了黑熊在准备穿越道路时，警惕性提升与威胁识别能力增强。黑熊对人类相关威胁的识别与警觉能力，是其在人类改造景观中生存的适应性特征。