Gibbons are apes in the family Hylobatidae, which is divided into four genera based on diploid chromosome number: Hylobates (44), Hoolock (38), Nomascus (52), and Symphalangus (50). Gibbons occur in tropical and subtropical rainforests from northeast India to Indonesia and north to southern China, including the islands of Sumatra, Borneo, and Java.
Their secret lies in a fluid, crouch-and-lunge technique. Their long, heavy arms, good for hanging from branches, act as pendulums to swing their weight forward as they uncoil from the crouch.
The researchers scanned an enclosure with lasers to build up a 3D model of the environment, then filmed a pair of gibbons in high definition as they jumped between branches.
By digitising the outline of each jumping gibbon frame by frame, they revealed how its centre of mass moved, and they calculated the forces needed to propel 6kg (a stone) of hairy ape through the air.
What they found was that, for their weight, gibbons manage to put more energy into their jumps than any known animal, five times as much as humans are able to muster.
If they jumped vertically with no run up, their centre of mass would clear 3.5m compared to humans' 60cm.
Rehabilitated gibbons cannot be returned alone into the wild, as they will be attacked by other pairs defending their territory.
So Brule attempts to pair up gibbons at the sanctuary, by match-making rescued apes.
"You can't put one male and one female in one cage and know for sure it will be a good pair," he says.
"You need to find the right character, the right gibbon with the right partner."
A gibbon dating agency is helping to reintroduce once captive apes into the forests of southeast Asia.
Unusually among apes, a male and female gibbon will mate and remain faithful to one another for life, reaffirming their bond with complex mating songs.
But across southeast Asia, gibbons are captured and illegally held as pets.
Now one conservationist is returning these apes to the wild, by first rescuing them, and then using his match-making skills to pair them up.
Gibbons have become the "forgotten apes" and many species will soon go extinct unless urgent action is taken.
So say primate experts who have made a call to action to save the crested gibbons of southeast Asia, which are the most vulnerable group of all apes.
For example, just 20 Hainan gibbons survive on one island in China, making it the world's rarest ape species.
The earliest-known primates date from about 70 million years ago (Macdonald, 1985). The greater apes (family Pongidae, gorillas, chimpanzees, bonobos, and orangutans) split off from the lesser apes (family Hylobatidae, gibbons and siamangs) 20 million years ago. Gibbon-like fossils have been found in Africa (from the Oligocene and Miocene), Europe (from the Miocene), and Asia (from the upper Pliocene and Pleistocene).
A gibbon family has a territory of about 30 to 50 acres of old-growth rain forest. Each morning upon awakening a family group of gibbons loudly announces its presence in the forest, using a territorial hooting call and menacing gestures. This call warns other gibbons to stay out of their territory (and especially away from the local fruit trees). This noisy display takes 1/2 hour or more every morning and is usually started by the adult female. The male and female have different calls.
The skulls of hylobatids resemble those of hominids, with very short rostra, enlarged braincases, and large orbits that face forward. Hylobatids are catarrhine primates; that is, their nostrils are close together and face forward and slightly downward. They lack cheek pouches and their stomach is not sacculated. Their teeth are similar to those of hominids.
Their dramatic form of locomotion, called brachiating, can move gibbons through the jungle at up to 35 miles (56 kilometers) an hour, bridging gaps as wide as 50 feet (15 meters) with a single swinging leap. Brachiating also gives gibbons the unique advantage of being able to swing out and grab fruits growing at the end of branches, which limits competition for their favorite foods.
Gibbons thrive on the abundant fruit trees in their tropical range, and are especially fond of figs. They will occasionally supplement their diet with leaves and insects.
While lar gibbons usually live in serial monogamous pairs, their reproductive system is complex and can be polyandrous, sometimes including flexible sexual relationships which often occur outside of the usual pair bond (Reichard 1995; Reichard & Barelli 2008). Polygamous mating has also been seen (Bartlett 2007). This is primarily due to the changing relationships among lar gibbons over their lifetimes, often including successive pairings with different mates and inclusion in different social group types (Reichard & Barelli 2008).
The 12 species of gibbons are classified, referring to their size, as lesser apes. They exhibit many of the general characteristics of primates: flat faces, stereoscopic vision, enlarged brain size, grasping hands and feet, and opposable digits; and many specific characteristics of apes: broad chest, full shoulder rotation, no tail, and arms longer than legs.
Gibbons are one of the few apes where the adult female is the dominant animal in the group. The hierarchy places her female offspring next followed by the male offspring and finally by the adult male.