How do Sumatran orangutans use tools to open hard-shelled fruit?

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An illustration of a female Bornean orangutan (Pongo pygmaeus) with long reddish-brown fur, hanging from tree branches with one arm extended upward and one leg hooked over a branch. A scale bar at the bottom shows lengths of 30 centimeters and 12 inches for size reference. — orangutan Female orangutans (*Pongo*) have the longest breeding interval of any mammal, giving birth on average once every eight years.

In the wild, Sumatran orangutans demonstrate sophisticated tool use to assist with foraging. Specifically, they have been observed defoliating sticks of an appropriate size to pry seeds from hard-shelled fruit.1

This behavior is part of a broader range of cognitive abilities, including causal reasoning and tool production, which these primates utilize to access food sources such as insects or honey from tree holes.1