Data from: Refuge or predation risk? Alternate ways to perceive hiker disturbance based on maternal state of female caribou

Human presence in natural environments is often a source of stress that is perceived by large ungulates as an increased risk of predation. Alternatively, disturbance induced by hikers creates a relatively predator-free space that may serve as a refuge. We measured the behavioral responses of female caribou to disturbance associated with the presence of hikers during summer in the Gaspésie National Park. We used those data to determine whether caribou responded negatively to human activity (i.e., the predation risk hypothesis) or whether human activity resulted in a decrease in the magnitude of perceived risk (i.e., the refuge hypothesis). Female caribou with a calf spent nearly half of their time feeding, regardless of the presence of a trail or the number of hikers. They also decreased their vigilance near trails when the number of hikers increased. Conversely, lone females fed less frequently and almost doubled the time invested in vigilance under the same circumstances. However, both groups of females moved away from trails during the day, especially in the presence of hikers. We demonstrated that risk avoidance was specific to the maternal state of the individual. Lactating females accommodated the presence of hikers to increase time spent foraging and nutritional intake, providing support for the refuge hypothesis. Alternatively, lone females with lower energetic requirements and no maternal investment in a vulnerable calf appeared less tolerant to risk, consistent with the predation risk hypothesis. Synthesis and applications: Hikers influenced the vigilance–feeding trade-off in caribou, underlining the importance of appropriate management of linear structures and human activities, especially across the critical habitat of endangered species. Even if some individuals seemed to benefit from human presence, this behavioral adaptation was not sufficient to reduce annual calf mortality associated with predation.

自然环境中的人类活动常构成应激源，大型有蹄类动物（large ungulates）会将其感知为捕食风险升高的信号。与之相对，徒步旅行者引发的干扰则会形成相对无捕食者的空间，可作为避难所。本研究于夏季在加斯佩西国家公园（Gaspésie National Park）开展，测定了雌性北美驯鹿（caribou）对徒步旅行者相关干扰的行为响应。我们利用所得数据，旨在验证两种假说：一是北美驯鹿会对人类活动产生负面响应（捕食风险假说（predation risk hypothesis）），二是人类活动会降低其感知到的风险强度（避难所假说（refuge hypothesis））。
带幼崽的雌性北美驯鹿会花费近半数时间觅食，无论步道是否存在或徒步旅行者的数量多寡；当徒步旅行者数量增加时，它们在步道附近的警戒行为（vigilance）也会有所减少。与之相反，独居雌性的觅食频率更低，且在相同情境下投入警戒行为的时间几乎翻倍。不过两类雌性均会在日间远离步道，在有徒步旅行者出现时尤为显著。
本研究证实，避险行为具有个体母性状态（maternal state）特异性。泌乳雌性（lactating females）会适应徒步旅行者的存在，以增加觅食时长与营养摄入，这为避难所假说提供了实证支撑。与之相对，能量需求更低且无需为脆弱幼崽投入母性资源的独居雌性，则对风险的耐受性更弱，这与捕食风险假说的预测相符。
综合与应用：徒步旅行者会影响北美驯鹿的警戒-觅食权衡（trade-off），凸显了对线性设施与人类活动进行合理管控的重要性，尤其是在濒危物种的关键栖息地（critical habitat）范围内。即便部分个体似乎能从人类活动中获益，这种行为适应性仍不足以降低因捕食导致的年度幼崽死亡率。