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Policing stabilizes construction of social niches in primates


All organisms interact with their environment, and in doing so shape it, modifying resource availability. Termed niche construction, this process has been studied primarily at the ecological level with an emphasis on the consequences of construction across generations1. We focus on the behavioural process of construction within a single generation, identifying the role a robustness mechanism2—conflict management—has in promoting interactions that build social resource networks or social niches. Using ‘knockout’ experiments on a large, captive group of pigtailed macaques (Macaca nemestrina), we show that a policing function, performed infrequently by a small subset of individuals3, significantly contributes to maintaining stable resource networks in the face of chronic perturbations that arise through conflict. When policing is absent, social niches destabilize, with group members building smaller, less diverse, and less integrated grooming, play, proximity and contact-sitting networks. Instability is quantified in terms of reduced mean degree, increased clustering, reduced reach, and increased assortativity. Policing not only controls conflict3,4,5, we find it significantly influences the structure of networks that constitute essential social resources in gregarious primate societies. The structure of such networks plays a critical role in infant survivorship6, emergence and spread of cooperative behaviour7, social learning and cultural traditions8.

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Figure 1: Schematic showing putative basins of attraction for pigtailed macaque social networks.
Figure 2: Empirically derived grooming and play networks in three conditions.
Figure 3: Reach and assortativity results.


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We thank E. Jen, E. Goldberg, J. Miller, E. Smith, D. Erwin, L. Marino, H. Gouzoules, C. Boehm, N. Ay, Y. Sato, M. Morris and J. Padgett for discussions, M. Seres for assistance with the data collection, and the animal care staff at YNPRC. YNPRC is fully accredited by the American Association for Accreditation of Laboratory Animal Care. This work was supported by the Packard Foundation (D.C.K.), the McDonnell Foundation (D.C.K., J.C.F., M.G.), the Wenner-Gren Foundation (J.C.F.), the Proteus Foundation (D.C.K.), the NSF (F.B.M.d.W.) and the NIH (F.B.M.d.W., J.C.F., D.C.K.).

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Correspondence to Jessica C. Flack.

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Supplementary Notes

This file contains Supplementary Figure 1 (illustration of social niche, overlapping networks), Supplementary Methods (removal procedure), Supplementary Data (detailed statistical results; analyses of potential nonpolicing functions performed by males; control analyses for removal of low-ranking female), Supplementary Table 1 (reach descriptive results) and Supplementary Notes (random graph generation procedure). (PDF 300 kb)

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Flack, J., Girvan, M., de Waal, F. et al. Policing stabilizes construction of social niches in primates. Nature 439, 426–429 (2006).

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