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How do flexible hip joints help orangutans climb and move through trees?

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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 the largest arboreal animals, and their ability to navigate the forest canopy is supported by specialized anatomical adaptations, including flexible hip joints.1

These flexible hip joints are essential because they allow orangutans to achieve a similar range of movement in their legs as they do in their arms. This mobility enables them to scramble through the trees using all four limbs, providing the versatility needed to grasp branches and move effectively through the complex environment of the forest canopy.1

While great apes possess long ischia—the lower part of the hip bone—that provide them with powerful hip extension for climbing trees, the flexibility of the hip joint itself is a key arboreal adaptation that distinguishes their movement from the more rigid, specialized bipedal structure found in humans. By allowing for this wide range of motion, the hip joints help orangutans maintain stability and maneuverability while climbing, feeding, and constructing sleeping platforms in the trees.12