Investigating medicinal resource combinations in the Bornean orangutan diet.

Self-medication occurs across diverse taxa, but identifying novel behaviours and medicinal resources remains challenging due to the need for long-term observation, intensive health monitoring, and costly pharmacological analyses. Recent advances in analytical methods have enabled the development of the self-medicative resource combination hypothesis (SMRCH), which proposes that non-human animals may deliberately combine therapeutic resources when ill. This framework has previously been applied to identify non-random dietary combinations in wild chimpanzees. Here, we extend this approach to another great ape by examining dietary combinations in wild Bornean orangutans (Pongo pygmaeus), a species with emerging evidence of medicative feeding behaviour, thereby enabling broader comparative insight into medicative feeding across great apes. Using long-term feeding data from a Sebangau peat-swamp forest Central Kalimantan, we analysed patterns of plant use and evaluated their potential medicinal relevance. Our analyses revealed non-random dietary combinations involving plant species with documented ethnomedicinal and pharmacological properties. These findings are consistent with the SMRCH, supporting its utility as a framework for identifying non-random dietary associations that may represent candidate self-medicative behaviours in orangutans and other great apes. This research highlights the importance of preserving Indigenous knowledge for biodiversity conservation and global health research.