Department of Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland.
Wild Nature Institute, Concord, NH, USA.
J Anim Ecol. 2021 Jan;90(1):212-221. doi: 10.1111/1365-2656.13247. Epub 2020 Jun 8.
Experimental laboratory evidence suggests that animals with disrupted social systems express weakened relationship strengths and have more exclusive social associations, and that these changes have functional consequences. A key question is whether anthropogenic pressures have a similar impact on the social structure of wild animal communities. We addressed this question by constructing a social network from 6 years of systematically collected photographic capture-recapture data spanning 1,139 individual adult female Masai giraffes inhabiting a large, unfenced, heterogeneous landscape in northern Tanzania. We then used the social network to identify distinct social communities, and tested whether social or anthropogenic and other environmental factors predicted differences in social structure among these communities. We reveal that giraffes have a multilevel social structure. Local preferences in associations among individuals scale up to a number of distinct, but spatially overlapping, social communities, that can be viewed as a large interconnected metapopulation. We then find that communities that are closer to traditional compounds of Indigenous Masai people express weaker relationship strengths and the giraffes in these communities are more exclusive in their associations. The patterns we characterize in response to proximity to humans reflect the predictions of disrupted social systems. Near bomas, fuelwood cutting can reduce food resources, and groups of giraffes are more likely to encounter livestock and humans on foot, thus disrupting the social associations among group members. Our results suggest that human presence could potentially be playing an important role in determining the conservation future of this megaherbivore.
实验室内的证据表明，社会系统被打乱的动物表现出较弱的关系强度，并且具有更多的排他性社会联系，这些变化具有功能后果。一个关键问题是人为压力是否对野生动物群落的社会结构产生类似的影响。我们通过从系统收集的照片捕捉-再捕获数据中构建了一个社交网络来解决这个问题，这些数据跨越了 1139 只成年雌性马赛长颈鹿，它们生活在坦桑尼亚北部一个大型、无围栏、异质的景观中。然后，我们使用社交网络来识别不同的社交群体，并测试社交或人为和其他环境因素是否预测了这些群体之间社会结构的差异。我们揭示了长颈鹿具有多层次的社会结构。个体之间关联的局部偏好会扩展到许多不同的、但空间上重叠的社会群体，这些群体可以被视为一个大型的相互连接的复合种群。然后，我们发现那些靠近传统的马赛人聚居地的社区表现出较弱的关系强度，并且这些社区中的长颈鹿在其联系中更加排他。我们在对人类接近程度的反应中所描述的模式反映了社会系统被打乱的预测。在 bomas 附近，砍伐燃料木材会减少食物资源，而且长颈鹿群更有可能在路上遇到牲畜和人类，从而破坏群体成员之间的社会联系。我们的研究结果表明，人类的存在可能在决定这种大型食草动物的保护未来方面发挥着重要作用。
