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为大型有蹄类动物带来应激，使其感知到捕食风险升高。而徒步旅行者引发的干扰则可能创造出相对安全的无捕食者空间，成为庇护所。
本研究于夏季在加斯佩西国家公园（Gaspésie National Park）开展，记录了雌性驯鹿对徒步旅行者干扰的行为响应，并通过分析相关数据，验证两种假说：一是人类活动会引发驯鹿的负面响应（即捕食风险假说（predation risk hypothesis）），二是人类活动会降低驯鹿所感知的风险水平（即庇护所假说（refuge hypothesis））。
带幼崽的雌性驯鹿无论步道是否存在、徒步旅行者数量多少，均会将近一半的时间用于觅食；且当徒步旅行者数量增加时，它们在步道附近的警戒行为会有所减少。与之相反，单独活动的雌性驯鹿觅食频率更低，且在相同环境下投入警戒的时间几乎翻倍。不过，两类雌性驯鹿在日间均会远离步道，在有徒步旅行者时这一行为尤为明显。
本研究证实，规避风险的行为与个体的母性状态密切相关。泌乳雌性驯鹿会适应人类徒步者的存在，增加觅食时间与营养摄入，这为庇护所假说提供了支持。而单独活动的雌性驯鹿能量需求更低，且无需为脆弱幼崽投入母性资源，因此对风险的耐受度更低，这与捕食风险假说相符。
总结与应用启示：徒步旅行者的活动会影响驯鹿的警戒-觅食权衡（vigilance–feeding trade-off）关系，这凸显了对线性设施与人类活动进行合理管理的重要性，尤其是在濒危物种的关键栖息地范围内。即便部分个体似乎能从人类活动中获益，但这种行为适应性并不足以降低由捕食引发的幼崽年死亡率。