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New paper on stable isotopic investigation of wild orangutans' diet
A new paper (co-)authored by NPO members was published in American Journal of Biological Anthropology.
Tsutaya T, Wong A, Malim PT, Bernard H, Ogawa NO, Ohkouchi N, Hongo S, Tajima T, Kanamori T, Kuze N. 2022. Stable isotopic investigation of the feeding ecology of wild Bornean orangutans. American Journal of Biological Anthropology 179: 276‒290.
https://doi.org/10.1002/ajpa.24598
Orangutans are critically endangered primate species in Southeast Asia. For effective conservation, it is essential to investigate the feeding ecology of wild orangutans. Detailed dietary data can be obtained by behavioral observation, but this is time-consuming and labor-intensive. Furthermore, it is difficult to observe individuals that are not habituated to humans. In this study, we applied stable isotope analysis (a method used in geoscience and other fields to estimate the origin of chemical compounds) to wild orangutans to evaluate this method's usefulness in studying the dietary ecology of wild orangutans. Carbon and nitrogen stable isotope ratios were measured for fecal and food samples collected from Danum Valley Conservation Area over an 18-month period. Carbon and nitrogen stable isotope ratios are recorded in body tissues and feces, so they can be used to estimate the content and amount of food an individual has consumed. However, our analysis revealed that, unlike African rainforests, the stable isotope ratios of plant foods from Dunam Valley are homogeneous and are not so effective in estimating the feeding ecology of the primary forest. However, it is also suggested that dietary contributions from agricultural landscapes and logged forests under anthropogenic influence can easily be estimated in orangutans using stable isotope analysis. Stable isotope analysis of feces is a potential new conservation tool that can easily and quickly estimate anthropogenic changes in the diet of wild orangutans.
https://doi.org/10.1002/ajpa.24598
Orangutans are critically endangered primate species in Southeast Asia. For effective conservation, it is essential to investigate the feeding ecology of wild orangutans. Detailed dietary data can be obtained by behavioral observation, but this is time-consuming and labor-intensive. Furthermore, it is difficult to observe individuals that are not habituated to humans. In this study, we applied stable isotope analysis (a method used in geoscience and other fields to estimate the origin of chemical compounds) to wild orangutans to evaluate this method's usefulness in studying the dietary ecology of wild orangutans. Carbon and nitrogen stable isotope ratios were measured for fecal and food samples collected from Danum Valley Conservation Area over an 18-month period. Carbon and nitrogen stable isotope ratios are recorded in body tissues and feces, so they can be used to estimate the content and amount of food an individual has consumed. However, our analysis revealed that, unlike African rainforests, the stable isotope ratios of plant foods from Dunam Valley are homogeneous and are not so effective in estimating the feeding ecology of the primary forest. However, it is also suggested that dietary contributions from agricultural landscapes and logged forests under anthropogenic influence can easily be estimated in orangutans using stable isotope analysis. Stable isotope analysis of feces is a potential new conservation tool that can easily and quickly estimate anthropogenic changes in the diet of wild orangutans.
