[ Hylobates concolor leucogenys ]
Swingin’ In the Rain
||18 to 25 inches
||mainly fruit, but also leaves, buds, flowers, and occasionally insects, eggs, and birds
||monkey chow biscuits, canned moist food, and a wide variety of fruits, vegetables, and leafy greens
||Laos, Vietnam, and southeastern China
||tropical rain forests
Highway in the sky
White-cheeked gibbons are among the most agile of all mammals. These long-armed primates swing with an effortless grace through the rain forests of southeast Asia, using trees like a highway in the sky. They swing with one arm, then the other, moving along the undersides of branches and vines, with their legs flexed under their body. This form of locomotion is called brachiation.
How do they do that?
Gibbons are well-adapted for moving fast in trees. They have a small, lightly-built body, and their arms and hands are long, which helps them gain a secure grip as they grasp one branch and then another. They can cover more than ten feet in a single swing between branches, and leap 20 feet from a standstill. Even though they make it look easy and falls are rare, tree travel is still dangerous.
Of the two hundred fifty or so species of primate in the world, gibbons are among the best suited to a life in the trees. They rarely descend to the ground, but when they do, they walk on their hind legs while suspending their arms overhead to maintain balance—giving the appearance of walking an imaginary tightrope. There are eleven species of gibbon, and white-cheeked gibbons are more endangered than most. They are so dependent on life in the trees that if their forest homes are destroyed for logging or agriculture they can’t survive in any other kind of habitat.
Male and female white-cheeked gibbons are strikingly different in color. In fact, they look like different species. Females have buff or cream-colored fur, with a tiny patch of black on top of their head. Males are all black except for white patches on their cheeks. When baby gibbons are born, their fur is the same buff color as their mom’s (an effective form of camouflage), but they turn all black by one year of age. Then, as they become young adults, female infants turn back to the buff color, while males remain black.
Mated pairs of gibbons are very territorial. They mark their territory primarily through loud vocal displays, the sounds of which travel hundreds of yards through the forest. In advertising their ownership of a territory and to strengthen the bond between them, male and female gibbons perform a sort of duet. The females’ part is a long rising series of notes that end in a fast "twitter." The male’s song is not as complicated as the female’s. He grunts, squeals, and whistles. But their duet is strangely beautiful.
To a neighboring group of gibbons, the call means, "Keep out!" To people who live in the forest, the long and loud duet is a welcome sign of the forest’s health, because gibbons are considered good spirits.
White-cheeked gibbons at Brookfield Zoo
Tropic World: Asia is home to Brookfield Zoo’s family of white-cheeked gibbons. Benny is the adult male, and mate to Indah. They are easy to tell apart because Benny has black fur, while Indah’s is light brown. Their son Melouprey was born in December 1998. After fully maturing, he recently departed for another zoo where he will be matched up with a female.
Brookfield Zoo is a member of the Gibbon Species Survival Plan (SSP), which manages all species of gibbons in North American zoos. SSPs are cooperative programs among zoos that oversee the breeding of endangered animals. Brookfield Zoo participates in more than 30 SSPs.
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