White-handed or Lar gibbon (Hylobates lar)White-handed or Lar gibbon (Hylobates lar)

Gibbons spend about 99% of their time high up in the treetops and can go for years without coming down to the ground. Everything they need can be found in the forest canopy, including water trapped in tree crevices or in the stunning bowl-like bromeliad flowers.

Physical description: Gibbons have much longer arms than legs, which makes them perfectly adapted for travelling through treetops at high speeds. White-handed gibbons have white hands and feet, and also a white ring around the face. Their fur can be beige, red, brown or black. This colouration is not dependent on age or gender, and does not necessarily reflect their parents' fur colour either. When standing upright, gibbons are roughly 80cm tall and they weigh around 5-6kg, males being about 1kg heavier than females. Both have equally large canines.

Habitat: White-handed gibbons occur in highly fragmented areas of evergreen rainforest in Thailand, Laos, Myanmar, Peninsular Malaysia, the Indonesian island of Sumatra and the Chinese Yunnan province. Some live in dryer, more seasonal environments or in secondary forests, but gibbon population density is highest in areas of greater plant diversity. They spend most of their time high up in the forest canopy, above 25m. Other species of gibbon occur between southern China, eastern India and the central islands of the Indonesian archipelago.

Diet: Much of a gibbon's diet consists of fruit, particularly figs, but they really like leaves and insects too. Gibbons also eat flowers, seeds, tree bark, small birds, new stems, buds, shoots and eggs. The gibbons at Monkeyland particularly like sweet fruit such as banana or guava.

Life history: Females have their first offspring at the age of about 9 years, after a gestation period of around 7 months. For the first two years of its life, an infant gibbon is carried everywhere by its mother as it clings on to her belly. Thereafter, the little gibbon is weaned and can move around independently, but will closely follow its mother for at least another 3 years. Gibbons reach sexual maturity at around 7 years, but may continue to live within/on the borders of their parent's territory for several more years until settling into their own area with a mate. Gibbons live to an average of 44 years.

Associations: In the wild, lar gibbons associate with siamangs, pileated gibbons and dark-handed gibbons. There is evidence of hybrid offspring between lar gibbons and the two types of gibbons they interact with in the wild. At Monkeyland the gibbons have been seen to groom capuchin monkeys, spider monkeys, squirrel monkeys and even a staff member's dog! In fact, our resident male Atlas seems to think that he is a capuchin and usually travels with their troop, showing little or no interest in humans or other gibbons.

Social structure: Typically, gibbon groups include 3-5 individuals, although anything up to 11 gibbons living together has been recorded in the wild and sometimes they even lead solitary lifestyles. Gibbons were once thought to be the most monogamous primate, always living in a nuclear family unit including the mother, father and sexually immature offspring. It was said that once the young reach adulthood at around 7 years of age, they are chased out of the territory just like any other adult stranger. However, recent evidence suggests that this may not be the case. Contrary to popular belief, gibbons do often live in groups containing more than two adults and flings or divorces are not unheard of.

Territorial marking: It seems that gibbons rely on vocalisations for territorial marking, although their language is not well understood by humans and many different interpretations can be found to explain their beautiful songs.

White-handed or Lar gibbon (Hylobates lar) Communication: Gibbon vocalisations include short sounds referred to as "calls" and longer vocalisations called "songs". The pleasant songs of our three Monkeyland gibbons can be heard up to 5km away if the wind is right! Male gibbons may sing solo and pairs can be heard rehearsing astounding duets together, which may have the function of strengthening their bond. Vocalisations are used to mark the singer's territory and may also serve to keep the group spaced out correctly or to encourage cooperation with each other. Typically, gibbons sing an early morning song just after sunrise, but they may also sing during the day.

Mating: Mating typically occurs between a bonded pair, but around 15% of matings are extra-pair copulations. Females have an oestrus cycle of around 27 days and a birth interval of 2.5 years.

Other behaviour: To travel through the forest, gibbons use a process known as "brachiation". This means that they suspend themselves below branches using their arms and thereby swing beneath branches rather than walking on top. When they are in a hurry, gibbons may let go and literally fly short distances through the air before setting their next hand down on a branch. Gibbons can travel at speeds of up to 30km per hour. It seems that they are able to do this by having a mental map of their forest territories and planning each grip several steps in advance. Unlike most other apes, gibbons do not build nests. They sleep on open branches, usually leaving the safer spots high up in the canopy for females with infants or juveniles. Adults never share a sleeping spot and they rarely sleep in the same place twice. Gibbons are quite good at walking on two feet along the ground. Although this behaviour is almost absent in wild gibbons, it is commonly observed in captive gibbons. Our resident gibbon Atlas is particularly good at bipedal walking, and even keeps his long arms neatly hanging down the sides of his body rather than waving them comically above his head, as many other gibbons do.

Conservation: Most subspecies of Hylobates lar are classed as lower risk/near threatened by the IUCN. The Yunnan Lar from Southern China, however, has been classed as critically endangered. More data regarding differences between subspecies needs to be collected in order to assess the number of species and subspecies and their numbers in the wild. . The greatest threat to gibbons is the fragmentation of their habitats due to logging, mining and agriculture. This results in isolated populations and genetic stagnation. Sanctuaries all over South East Asia are also filled with ex-pet gibbons, who are not easily kept in captivity. In fact, they are extremely strong and can be harmful to humans, whom they often turn on after becoming sexually mature.

Did you know? Gibbons are not monkeys. Like us, they are in the primate suborder of the apes. You can easily distinguish apes from monkeys since apes do not have tails.

References:

Eudey, A. & Members of the Primate Specialist Group 2000. Hylobates lar ssp. lar. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 16 July 2006.

Fuentes, A. (2000) Hylobatid communities: changing views on pair bonding and social organization in hominoids. Yearbook of Physical Anthropology 43, 33-60.

Reichard, U. (1998) Sleeping sites, sleeping places, and presleep behaviour of gibbons (Hylobates lar). American Journal of Primatology, 46, 35-62.

www.birdsofeden.co.za Information supplied by:
Lara Mostert

www.monkeyland.co.za
www.birdsofeden.co.za

South Africa WILD ANIMAL CLUBS, ORGANISATIONS AND ASSOCIATIONS