Stable isotope analysis of hair from bonobos shows that the diet of these great apes may vary with social rank and reproductive status, according a study published Sept. 14, 2016 in the open-access journal PLOS ONE by Vicky Oelze from Max Planck Institute for Evolutionary Anthropology, Germany, and colleagues.
Great ape diets vary with environmental conditions as well as with sociodemographic factors, and the former can obscure the impact of the latter. Bonobos, however, are ideal for assessing social and physiological influences on diet because they live in the Congo Basin's ecologically steady evergreen rainforest, which has relatively little seasonal variation. Oelze and colleagues analyzed stable nitrogen and carbon isotopes in local plant foods and 101 hair samples collected from 23 adult bonobos between 2008 and 2010.
The researchers found that social rank may have affected diet only in male bonobos: nitrogen was low in hairs from adolescent males, which are low-ranking and commonly excluded when meat is shared. In addition, nitrogen and carbon in hairs from females varied with reproductive status, presumably reflecting varying dietary needs and physiological conditions. Notably, nitrogen isotope values were high during pregnancy, which may reflect the mobilization and metabolism of body-own proteins. Likewise, during pregnancy, carbon isotope values were particularly low --suggesting a high protein diet based on terrestrial herbaceous vegetation. In contrast, carbon isotope values were high during lactation-- suggesting an energy rich diet based on high calorie fruits when energy demands increase to nurse and carry dependent offspring. The researchers recommend testing their findings in other primate species.
"The study non-invasively investigates the dietary pattern of a community of wild bonobos over two years by using stable isotope analysis in hair and integrating long-term sociodemographic data," says Vicky Oelze. "Beside dietary differences in male bonobos related to dominance rank, the authors found that female bonobo isotope values differed between different stages of reproduction, which can be related to changes in dietary needs and preference during pregnancy (high protein diet) and lactation (high energy diet)."
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Citation: Oelze VM, Douglas PH, Stephens CR, Surbeck M, Behringer V, Richards MP, et al. (2016) The Steady State Great Ape? Long Term Isotopic Records Reveal the Effects of Season, Social Rank and Reproductive Status on Bonobo Feeding Behavior. PLoS ONE 11(9): e0162091. doi:10.1371/journal.pone.0162091
Funding: This project was generously funded by the Wenner-Gren-Foundation (Grant 8573 "Isotope Ecology of the Salonga Bonobo - Tracing Dietary Variation and Seasonality by Stable isotope Analyses of Hair", October 2011).
Competing Interests: The authors have declared that no competing interests exist.