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Why is ripe fruit an important food for orangutans?

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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.

Orangutans are predominantly ripe-fruit eaters, and fruit serves as a vital component of their diet because it avoids the specific constraints associated with other food sources.12

Unlike insects, which are small and difficult for large animals to catch in sufficient quantities to sustain their energy needs, or leaves, which contain cellulose and hemicellulose that require complex and time-consuming digestive processes, fruit does not present these limitations. As the largest arboreal animals, orangutans rely on this efficient food source to support their nutritional requirements while spending the majority of their time in the trees.12