This study explores diet differences between two populations of wild Bornean orangutans (Pongo pygmaeus wurmbii) to assess whether a signal of social learning can be detected in the observed patterns. The populations live in close proximity and in similar habitats but are separated by a river barrier that is impassable to orangutans in the study region.
We found a 60% between-site difference in diet at the level of plant food items (plant species–organ combinations). We also found that individuals at the same site were more likely
to eat the same food items than expected by chance.