Department of Anthropology, One Shields Ave., University of California, Davis, CA 95616, USA; Animal Behavior Graduate Group, One Shields Ave., University of California, Davis, CA 95616, USA; Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.
Department of Anthropology, One Shields Ave., University of California, Davis, CA 95616, USA; Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.
J Hum Evol. 2018 May;118:1-13. doi: 10.1016/j.jhevol.2018.02.003. Epub 2018 Mar 3.
Predation is thought to have been a key selection pressure in primate evolution, especially in the savannah-woodland habitats where several early hominin species lived. However, predator-primate prey relationships are still poorly understood because human presence often deters predators, limiting our ability to quantify the impact of predation. Synchronized high-resolution tracking of leopards (Panthera pardus), vervets (Chlorocebus pygerythrus), and olive baboons (Papio anubis) during a 14-month study in Kenya revealed that increased vulnerability to leopard predation was not associated with higher encounter rates, smaller body size, smaller group size, or greater distance from refuges, contrary to long-standing inferences. Instead, the initiation, rate, timing, and duration of encounters, outcome of approaches, and predation events showed only a diel pattern of differential vulnerability. In the absence of human observers, vervets were more vulnerable during the day, whereas baboons were more vulnerable at night, but overall neither species was more vulnerable than the other. As our results show that leopards avoided baboons during the day and hunted them at night, we suggest that the same pattern would have applied to hominins-because they were even larger than baboons and bipedal, resulting in similarly offensive capability on the ground during the day but poorer agility in the trees at night, especially as they became committed bipeds. Drawing from hominid behavior and archaeopaleontological and ethnographic evidence, we hypothesize that ground-sleeping hominins initially dealt with this formidable threat by using stone tools to modify Acacia branches into 'bomas', thorny enclosures that provided nighttime shelter. The ability of hominins to create their own nightly refuges on the ground wherever Acacia spp. were available would have allowed them to range more widely, a crucial step in furthering the spread of hominins across Africa and beyond.
捕食被认为是灵长类动物进化的关键选择压力，尤其是在早期人类物种生活的稀树草原栖息地。然而，捕食者-灵长类动物猎物关系仍然知之甚少，因为人类的存在常常会吓走捕食者，限制了我们量化捕食影响的能力。在肯尼亚进行的为期 14 个月的研究中，对豹子（Panthera pardus）、长尾黑颚猴（Chlorocebus pygerythrus）和橄榄狒狒（Papio anubis）进行同步的高分辨率跟踪，结果表明，增加对豹子捕食的脆弱性与更高的遭遇率、更小的体型、更小的群体大小或离避难所更远无关，这与长期以来的推断相反。相反，遭遇的开始、频率、时间和持续时间、接近的结果以及捕食事件仅表现出昼夜差异的脆弱性模式。在没有人类观察者的情况下，长尾黑颚猴在白天更脆弱，而狒狒在晚上更脆弱，但总的来说，没有一种物种比另一种更脆弱。由于我们的结果表明豹子在白天避开狒狒，而在晚上捕猎它们，我们建议同样的模式也适用于人类——因为它们比狒狒更大，并且是两足动物，因此在白天的地面上具有类似的攻击性能力，但在晚上的树上敏捷性较差，尤其是当它们成为坚定的两足动物时。根据人类行为以及古人类学和民族志证据，我们假设，最初地面睡眠的人类使用石器将金合欢树枝改造成“bomas”（荆棘围栏）来应对这种可怕的威胁，这些荆棘围栏在夜间提供庇护。只要金合欢属植物可用，人类就有能力在地面上创建自己的夜间避难所，这使他们能够更广泛地活动，这是人类在非洲及其他地区进一步扩散的关键一步。
