Intra-and interpopulational differences in orangutan (Pongo pygmaeus) activity and diet: implications for the invention of tool use.

Tool manufacture and use have been described for wild orangutans (Pongo pygmaeus), with appreciable interpopulational differences in tool complexes. The ecological factors that contribute to these differences require investigation. Significant interpopulational differences in diet suggest that ecological factors contribute to variation in tool-based insect foraging.