Saito Miho, Bercovitch Fred B, Idani Gen'ichi
Department of Ethology, Graduate School of Human Sciences, Osaka University, 1-2 Yamada-oka, Suita, 565-0871, Japan; Wildlife Research Center, Kyoto University, 2-24 Tanaka-Sekiden-cho, Sakyo, Kyoto, 606-8203, Japan.
Wildlife Research Center, Kyoto University, 2-24 Tanaka-Sekiden-cho, Sakyo, Kyoto, 606-8203, Japan.
Behav Processes. 2020 Nov;180:104227. doi: 10.1016/j.beproc.2020.104227. Epub 2020 Aug 24.
Fission-fusion social systems involve the splitting and merging of subgroups with frequent changes in membership occurring as a result of a number of ecological and social factors, such as demographic processes including birth, movement, or death. Giraffe reside in fission-fusion social systems, and we studied how reproductive status influence associations among females, as well as how associations differ between calves and juveniles. Data were collected in Katavi National Park, Tanzania, during five study periods. We used social network analysis to identify whether reproductive status and developmental stages predict differences in giraffe social association. We found that females with offspring maintain stronger associations than females without offspring. We also revealed that calves and juveniles had similar network association patterns. Our results suggest that the presence of dependent offspring influences the social associations of females and individuals less than 1.5 years of age are still maintaining strong social associations with nursery group members. We conclude that nursery groups among giraffe are co-operative rearing units that probably reduce the costs of rearing to mothers, and may provide a group structure for animals to begin to develop skills useful for their future life in a fission-fusion social system.
裂变融合社会系统涉及亚群体的分裂和合并，由于诸多生态和社会因素，如包括出生、迁移或死亡在内的人口过程，成员会频繁变动。长颈鹿生活在裂变融合社会系统中，我们研究了繁殖状态如何影响雌性之间的关联，以及幼崽和幼年个体之间的关联有何不同。在五个研究期间收集了坦桑尼亚卡塔维国家公园的数据。我们使用社会网络分析来确定繁殖状态和发育阶段是否能预测长颈鹿社会关联的差异。我们发现有后代的雌性比没有后代的雌性维持着更强的关联。我们还发现幼崽和幼年个体有相似的网络关联模式。我们的研究结果表明，依赖后代的存在对雌性社会关联的影响较小，且不到1.5岁的个体仍与育儿群体成员保持着紧密的社会关联。我们得出结论，长颈鹿的育儿群体是合作育幼单位，这可能降低了母亲的育幼成本，并且可能为动物提供一种群体结构，使其开始发展对其在裂变融合社会系统中的未来生活有用的技能。
