Department of Biology, Regis University, Denver, CO 80221, USA.
Am J Phys Anthropol. 2012 Aug;148(4):580-8. doi: 10.1002/ajpa.22076. Epub 2012 May 3.
The multilevel society of hamadryas baboons, consisting of troops, bands, clans, and one-male units (OMUs), is commonly perceived to be an effective means of adapting to variable food availability while allowing spatial cohesion in response to predator pressure. The relationship between these variables, however, has never been tested quantitatively. The Filoha site in Awash National Park, Ethiopia is ideally suited to such an investigation as it contains nutrient-dense palm forests in addition to the Acacia scrublands typical of hamadryas distribution elsewhere, allowing comparisons of spatial cohesion across habitat types. Here, we use observations over a 1-year period to examine the relationship between resource availability, perceived predator pressure, and spatial cohesion in a band of wild hamadryas baboons at Filoha. Our results demonstrate that the band was more likely to break into OMUs when foraging in habitats with lower food availability, and that the band fissioned into independent clans more often when preferred resources were not available. Furthermore, the baboons remained in larger aggregations for longer periods of time (i.e., prior to embarking on their daily foraging route) on mornings after predators were heard in the vicinity, and increased cohesion in response to encounters with people who may have been perceived as predators. These results support the notion that hamadryas baboons change their social groupings in response to both food availability and predation risk and that the ability of hamadryas bands to cleave and coalesce in response to changes in these factors underlies the evolution of the hamadryas modular social structure.
多等级的阿拉伯狒狒社会由部队、乐队、氏族和单雄单位（OMU）组成，通常被认为是适应可变食物可获得性的有效手段，同时允许在响应捕食者压力时保持空间凝聚力。然而，这些变量之间的关系从未被定量测试过。埃塞俄比亚 Awash 国家公园的 Filoha 地点非常适合进行这样的调查，因为它除了含有狒狒分布在其他地方的典型金合欢灌丛外，还含有营养丰富的棕榈林，允许在不同的栖息地类型之间比较空间凝聚力。在这里，我们使用一年的观察结果来研究在 Filoha 的一个野生阿拉伯狒狒乐队中，资源可用性、感知捕食者压力和空间凝聚力之间的关系。我们的结果表明，当在食物供应较低的栖息地觅食时，乐队更有可能分裂成 OMU，并且当没有可用的首选资源时，乐队更频繁地分裂成独立的氏族。此外，当听到附近有捕食者时，狒狒在更大的群体中停留更长的时间（即在开始每天的觅食路线之前），并且在遇到可能被视为捕食者的人时，凝聚力会增加。这些结果支持了阿拉伯狒狒会根据食物可用性和捕食风险改变其社会群体的观点，并且阿拉伯狒狒乐队能够根据这些因素的变化分裂和合并是阿拉伯狒狒模块化社会结构进化的基础。
