Tool use among orangutans was first documented by Carel van Schaik. In 1994, Carel observed orangutans developing tools to help themselves eat, while conducting field work in Gunung Leuser National Park, in the northwest Sumatra.

Specifically the orangutans were using sticks to pry open pulpy fruits that have “Plexiglas needles” capable of delivering a painful jab covering them. Using the tools, the orangutans were getting past handling the prickly husk and into the nutritious fruit. From an anthropological viewpoint, tool use represents an aspect of culture, since the entire group participates in a behavior that has developed over time. One unique thing to clarify is that only Sumatran orangutans have been observed to use tools, not orangutans from Borneo.