A new paper (co-)authored by NPO members was published in Primates.

Tsutaya T, Ogawa NO, Nomura T, Shimizu M, Ohkouchi N, Kuze N. 2021. Carbon and nitrogen stable isotopic offsets between diet and hair/feces in captive orangutans. Primates 62: 945‒954.
https://doi.org/10.1007/s10329-021-00940-8

We have estimated stable isotopic offset values for orangutans, which are important for studies of feeding ecology. This will be useful for estimating the diet of wild orangutans in the future.