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How do flexible hip joints help orangutans move in 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 possess flexible hip joints that serve as a key arboreal adaptation, allowing them to achieve similar ranges of movement in their legs and arms. This flexibility is essential for their life in the canopy, where they frequently scramble through the trees using all four limbs. By enabling this high degree of mobility, these joints allow orangutans to navigate complex forest environments effectively, facilitating their ability to reach, climb, and move through the trees with the agility required of the largest arboreal animals.1