CEFE, CNRS, Univ. Montpellier, Univ. Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France.
Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, Recanati-Kaplan Centre, Oxford, UK.
J Anim Ecol. 2019 Jan;88(1):92-101. doi: 10.1111/1365-2656.12910. Epub 2018 Oct 22.
Diel migrations (DM; back and forth diel movements along an ecological gradient) undertaken by prey to avoid predators during the day have been demonstrated in many taxa in aquatic ecosystems. In terrestrial ecosystems, prey often shift between various vegetation types whose cover determine their vulnerability (i.e., likelihood of being killed when attacked). We conceptualized that in terrestrial ecosystems, DM could also occur and that the contribution of DM and shifts in vegetation cover use in reducing predation risk should depend upon the predator behaviour and the correlation between encounter risk and vulnerability across vegetation types. We further hypothesized that when the predator distribution is predictable, terrestrial prey could have evolved DM strategies taking them away from the predator when it is active or efficient. We investigated whether plains zebras Equus quagga perform DM in Hwange National Park (Zimbabwe). There, zebras can forage in large patches of open grasslands located near waterholes where they can also easily detect predators. However, they are there at high risk of encountering their main predator, lions Panthera leo, especially at night. We found out that zebras employ a DM anti-predator strategy. Zebras forage near waterholes during the day but move away from them at sunset, when lions become active. We demonstrated that this DM, occurring over a few kilometres, dramatically reduces their night-time risk of encountering lions, which generally remain close to waterholes. Zebra changes in night-time selection for vegetation cover types reduced their risk of encountering lions much less. This may arise from a trade-off between encounter risk and vulnerability across vegetation types, with zebras favouring low vulnerability once DM has reduced encounter risk. In summary, here we (a) quantify, in a terrestrial system, the effect of a predator-induced DM on the likelihood of encountering a predator and (b) distinguish the effects of the DM on encounter risk from those related to day/night changes in selection for vegetation types. We discuss how prey partition their risk between encounter risk and habitat-driven vulnerability and why it is likely critical to understand the emergence of anti-predator behavioural strategies.
昼夜迁移（DM；沿着生态梯度来回昼夜移动）是猎物为了避免白天被捕食者捕食而进行的，在水生生态系统的许多类群中都有证明。在陆地生态系统中，猎物经常在各种植被类型之间转移，这些植被类型的覆盖决定了它们的脆弱性（即受到攻击时被杀死的可能性）。我们认为，在陆地生态系统中，DM 也可能发生，DM 和植被覆盖使用的变化在降低捕食风险方面的贡献应该取决于捕食者的行为以及不同植被类型之间的遭遇风险和脆弱性的相关性。我们进一步假设，当捕食者的分布是可预测的时候，陆地猎物可能已经进化出了 DM 策略，当捕食者活跃或高效时，它们会远离捕食者。我们调查了平原斑马 Equus quagga 是否在津巴布韦的万基国家公园（Hwange National Park）表现出 DM。在那里，斑马可以在靠近水坑的大片开阔草原上觅食，在那里它们也可以很容易地发现捕食者。然而，它们在那里处于遭遇主要捕食者狮子 Panthera leo 的高风险中，尤其是在夜间。我们发现斑马采用了 DM 来抵御捕食者的策略。斑马在白天靠近水坑觅食，但在日落时，也就是狮子活跃的时候，它们会离开水坑。我们证明，这种跨越几公里的 DM 显著降低了它们夜间遭遇狮子的风险，狮子通常会靠近水坑。斑马在夜间对植被覆盖类型的选择变化，大大降低了它们遭遇狮子的风险。这可能是由于不同植被类型之间的遭遇风险和脆弱性之间的权衡，一旦 DM 降低了遭遇风险，斑马就会优先选择低脆弱性的植被类型。总之，在这里，我们（a）在陆地系统中量化了捕食者诱导的 DM 对遭遇捕食者的可能性的影响，（b）区分了 DM 对遭遇风险的影响与与白天/夜间选择植被类型变化有关的影响。我们讨论了猎物如何在遭遇风险和栖息地驱动的脆弱性之间分配风险，以及为什么了解抗捕食者行为策略的出现很可能是至关重要的。
