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There are at least twelve species of gibbons, which make up the family Hylobatidae. WARF works with the white-handed or lar gibbon (Hylobates lar) and Pileated Gibbon, two of four gibbon species found in Thailand. There are five sub-species of lar gibbon and we work with Hylobates lar entelloides, found in the western, central and southern areas of Thailand. Some people question placing gibbons with other apes in one family. Sometimes the lar gibbon is placed in a family of their own (Hylobatidae) or in a sub-family (Hylobatinae) within the family of the much heavier apes. The distribution areas of the different gibbon species do not overlap (allopatric), except for the Siamang that lives in the same area as the white-handed gibbon and the dark-handed gibbon (sympatric).
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Hylobates lar |
Behavior
Gibbons are small apes weighing approximately 6 kg, living as single, territorial, family groups with three to six individuals, a monogamous pair and up to four offspring. They live in the middle and upper canopy of the tropical rain forests in many parts of southern Asia, from northeastern India and southern China through to Sumatra, Borneo and Java (Indonesia.)
Gibbons live in small family-groups consisting of a mother and father and have babies every 3-4 years. Male and female appear to be on equal footing within the gibbon family. Like other apes they mature very slowly. In its first year the offspring is completely dependent on its mother. After three years it can move around independently and at that time the mother becomes receptive to the male again. They reach adulthood at six to eight years of age. When the young becomes an adolescent (at four to five years of age), it leaves the family because at this time the same-sex parent does not tolerate it in its territory anymore: mothers are hostile towards their daughters, fathers towards their sons. The parent harasses the young more and more and eventually drives it out of the family and the territory. The young gibbon tries to find a partner and develop a territory of its own. This expulsion is important as it prevents inbreeding and too much pressure on the food-resources in the territory. The life expectancy of gibbons is about 30 years.
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Hylobates pileatus (Female) |
The territory of a gibbon family measures 20 to 30 hectares. In the morning they claim their territory by singing. The gibbon's song is very loud and complex song with pure, melodious and sonorous tones. When the female is singing, the females of the neighbouring territory respond. This can be heard very clearly at the gibbon centre. This beautiful, somewhat melancholic sound characterizes the South East Asian rain forest. The females establish their territory by singing to each other. In between the males make simpler quivering sounds, but when the females sing, the males keep quiet, as they should. It takes a lot of years before a female is a proficient singer. It takes years of practice before a gibbon is a proficient singer. Every species of gibbon sings its own special song.
After the morning duet the family spends most of the day looking for food. Their long high-pitched calls can travel over a kilometre, and gibbons are often called 'the singing ape'. Once heard in great numbers throughout much of Thailand, many of their forests have now sadly become silent, this has given more meaning to the Karen people's saying. "When you kill a gibbon you leave seven lonely rivers."
Every now and then, while foraging for food, gibbons will come together to groom; dirt and parasites are removed from the fur and wounds are cleaned. Grooming is not only important from a hygienic point of view, but it also has a social group-bonding function. In the evening, the gibbons do not build a nest for the night like other apes, but sleep in an upright position. They fold their hind legs in front of their chest and put their hands on their knees, while their head nods on their chest.
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Foraging |
Drinking |
Gibbons have a hairless callosity on their bottom. They share some characteristics with humans which other apes do not. For instance, most apes walk on their knuckles and use their hands and feet while walking. Gibbons on the contrary, walk on their hind legs and can do so even when moving through trees. This 'human feature' and their big eyes, expressive and intelligent faces and cuddliness make gibbons very popular as pets and entertainment with people. The fact that they live in small family-groups, consisting of a mother and father and a few youngsters, makes them even more popular. Male and female appear to be on equal footing within the family structure.
Diet and locomotion
Unique to these apes is their way of moving through the trees: their arm-swinging locomotion is known as 'brachiation'. Gibbons can reach speeds of up to 30 kilometres an hour swinging through the trees, making them the fastest flightless animals in the forest. The thumbs of both the hands and the feet are opposable and very small so they don't interfere with their swinging. The gibbons only use their four fingers during swinging. A gibbon can hang quite easily on one hand.
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| Artocarpus-rigidus: Eating fruit of tree Artocarpus lanceifolius (MORACEAE ) |
Sandoricum-koetjape: Eating fruit of tree Sandoricum koetjape (MILIACEAE) |
Gnetum-sp A: Eating fruits of Gnetum sp . (GNETACEAE) |
Uvaria-leptopodaA : Eating fruit of Uvaria leptopoda .(ANNONACEAE ) |
Threats
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In Thailand huge tracts of forest are disappearing at an alarming rate, destroying the habitats of many species of flora and fauna. Gbbons and their habitat are one of the most vulnerable species. They are poached for meat, medicine and the illegal pet trade. This has left some of the remaining forest under-populated or extinct of gibbons. Gibbons are classified under Appendix One in the Convention for International Trade of Endangered Species (CITES) and it has been illegal to acquire a gibbon for a pet in Thailand since 1992, yet regretfully, this practice still continues today.
Gibbons used for pets are taken in their infancy, as they are easy to handle, very affectionate, intelligent, acrobatic and have that eerie human-like quality when young. To acquire a pet infant gibbon, a family of gibbons is hunted down and the mother gibbon carrying the baby is shot. Usually they are high up in the tops of the trees when this happens. Only one in every three infants manages to survive this ordeal. The killing of the mother gibbons also greatly reduces the overall reproduction rate of wild gibbons, which is steadily declining every year.
The baby gibbons that survive are reared as pets, commonly on a sub-standard diet without enough space to move and exercise and deprived of the company of other gibbons. On reaching sexual maturity at around 6-7 years the gibbons develop large canines and become aggressive and unpredictable. The once-loveable pet then becomes a dangerous wild animal and cannot be controlled, so is no longer wanted and is cruelly restricted with chains or small cages. Some are abandoned or given to the Thai authorities whose sanctuaries have limited housing. This glut of wild-born captive gibbons has created a problem for the Thai government who must house and manage these gibbons. As well as these unwanted pets other gibbons are confiscated from appalling conditions in bars and restaurants, where they are sometimes kept drugged or abused, and used as entertainment for the tourist trade. Fortunately some of these rescued gibbons are given to the GRP and through the rehabilitation process are sometimes finally put back into the rainforest where they belong, where the population can re-establish itself in the areas where they were once extinct.
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Species of gibbon
Gibbons have beautiful, thick fur. In some species the male and the female have different colours, but this is not the case with the white-handed lar. The colour of the White-handed gibbon varies from blond to black with brown and reddish colour-varieties as well. Their face, hands and feet are marked with white fur lining. The colour of the fur is no indication of the gender of the white-handed gibbon. In the southern parts of their habitat, dark-coloured gibbons are more common than light ones. In the wild, the dark animals have a preference for dark mates and the light animals prefer light mates. The reason for this is not known.
