Haub School of Environment and Natural Resources, University of Wyoming, Laramie, Wyoming, USA.
Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Laramie, Wyoming, USA.
J Anim Ecol. 2024 Apr;93(4):447-459. doi: 10.1111/1365-2656.14056. Epub 2024 Feb 13.
Predation risk is a function of spatiotemporal overlap between predator and prey, as well as behavioural responses during encounters. Dynamic factors (e.g. group size, prey availability and animal movement or state) affect risk, but rarely are integrated in risk assessments. Our work targets a system where predation risk is fundamentally linked to temporal patterns in prey abundance and behaviour. For neonatal ungulate prey, risk is defined within a short temporal window during which the pulse in parturition, increasing movement capacity with age and antipredation tactics have the potential to mediate risk. In our coyote-mule deer (Canis latrans-Odocoileus hemionus) system, leveraging GPS data collected from both predator and prey, we tested expectations of shared enemy and reproductive risk hypotheses. We asked two questions regarding risk: (A) How does primary and alternative prey habitat, predator and prey activity, and reproductive tactics (e.g. birth synchrony and maternal defence) influence the vulnerability of a neonate encountering a predator? (B) How do the same factors affect behaviour by predators relative to the time before and after an encounter? Despite increased selection for mule deer and intensified search behaviour by coyotes during the peak in mule deer parturition, mule deer were afforded protection from predation via predator swamping, experiencing reduced per-capita encounter risk when most neonates were born. Mule deer occupying rabbit habitat (Sylvilagus spp.; coyote's primary prey) experienced the greatest risk of encounter but the availability of rabbit habitat did not affect predator behaviour during encounters. Encounter risk increased in areas with greater availability of mule deer habitat: coyotes shifted their behaviour relative to deer habitat, and the pulse in mule deer parturition and movement of neonatal deer during encounters elicited increased speed and tortuosity by coyotes. In addition to the spatial distribution of prey, temporal patterns in prey availability and animal behavioural state were fundamental in defining risk. Our work reveals the nuanced consequences of pulsed availability on predation risk for alternative prey, whereby responses by predators to sudden resource availability, the lasting effects of diversionary prey and inherent antipredation tactics ultimately dictate risk.
捕食风险是捕食者和猎物在时空上重叠的函数，以及相遇时的行为反应。动态因素（例如群体大小、猎物可利用性以及动物的运动或状态）会影响风险，但很少将其纳入风险评估中。我们的工作针对的是一个系统，其中捕食风险与猎物丰度和行为的时间模式密切相关。对于新生有蹄类猎物，风险是在分娩脉冲期间的一个短暂时间窗口内定义的，随着年龄的增长，动物的运动能力增加，以及防御捕食的策略都有可能影响风险。在我们的郊狼-骡鹿（Canis latrans-Odocoileus hemionus）系统中，利用从捕食者和猎物收集的 GPS 数据，我们检验了共同天敌和生殖风险假说的预期。我们提出了两个关于风险的问题：（A）主要和替代猎物栖息地、捕食者和猎物活动以及生殖策略（例如分娩同步和母体防御）如何影响遇到捕食者的幼仔的脆弱性？（B）同样的因素如何影响捕食者在遭遇前后的行为？尽管在骡鹿分娩高峰期，骡鹿的选择增加，郊狼的搜索行为加剧，但通过捕食者淹没，当大多数幼仔出生时，幼鹿的个体遭遇风险降低，从而使它们免受捕食。在兔子栖息地（Sylvilagus spp.；郊狼的主要猎物）中生存的骡鹿面临最大的遭遇风险，但兔子栖息地的可利用性并没有影响捕食者在遭遇期间的行为。在有更多骡鹿栖息地的地区，遭遇风险增加：郊狼相对于鹿栖息地改变了它们的行为，而在遭遇期间，骡鹿的分娩脉冲和幼鹿的运动引起了郊狼速度的增加和运动轨迹的扭曲。除了猎物的空间分布外，猎物可利用性和动物行为状态的时间模式也是定义风险的基础。我们的工作揭示了脉冲可用性对替代猎物捕食风险的细微影响，捕食者对突然出现的资源可用性的反应、分散猎物的持久影响以及固有的防御捕食策略最终决定了风险。
