The La r
Gibbon (Hylobates lar), also known as the White-handed Gibbon, is a
primate in the Hylobatidae or gibbon family. It is one of the more
well-known gibbons and is often seen in zoos.The range of the Lar
Gibbon historically extended from southwest China and eastern Myanmar to
Thailand and Burma down the whole Malay Peninsula in primary and
secondary tropical rain forests. It is also present in the northwest
portion of the island of Sumatra. In recent decades, especially the
continental range has been reduced and fragmented, and the animals are
thought to be extinct in China.The gibbon genus is highly allopatric,
usually separated by large rivers. The Lar Gibbon shares its range with
only the siamang, Symphalanges syndactylus, on the tip of the Malaysian
peninsula and Sumatra.
Appearance
The fur coloring of the Lar Gibbon varies from black and dark-brown
to light brown sandy colors. The hands and feet are white colored,
likewise a ring of white hair surrounds the black face. Both males and
females can be all color variants, and the sexes also hardly differ in
size. Gibbons are true brachiators, propelling themselves through the
forest by swinging under the branches by their arms. Reflecting this
mode of locomotion, the white-handed gibbon has curved fingers,
elongated hands, extremely long arms and relatively short legs, giving
it an intermembral index of 129.7, one of the highest of the primates.
As with all apes, the number of caudal vertebrae have been reduced
drastically, resulting in the loss of a functional tail.
Diet and Dentition
The Lar Gibbon is considered frugivorous with fruit constituting 50%
of its diet, but leaves (29%) are a substantial part, with insects (13%)
and flowers (9%) forming the remainder Its dental formula is
2.1.2.3/2.1.2.3, the generalized formula for Old World monkeys and apes.
The dental arcade is U-shaped, and the mandible is thin and light. The
incisors are broad and flat, while the molars have low, rounded cusps
with thick enamel. The most noticeable characteristic of the dentition
of Hylobates lar is the presence of large, dagger-like canines in both
the upper and lower jaw. These canines are not sexually dimorphic.
Behavior
Lar Gibbons are diurnal and arboreal, inhabiting rain forests. They
rarely come to the ground, instead using their long arms to brachiate
through the trees. With their hooked hands they can move swiftly with
great momentum, swinging from the branches. Its social organization is
dominated by monogamous family pairs, with one breeding male and one
female along with their offspring. When a juvenile reaches sexual
maturity, it is expelled from the family unit. However, this traditional
conception has come under scrutiny. Long-term studies conducted in Khao
Yai National Park in Thailand suggest that their mating system is
somewhat flexible, incorporating extra-pair copulations, partner changes
and polyandrous groupings.
Family groups inhabit a firm territory, which they protect by warding
off other gibbons with their calls. Each morning the family gathers on
the edge of its territory and begins a "great call," a duet between the
breeding pair. Each species has a typified call and each breeding pair
has unique variations on that theme. The great call of Hylobates lar is
characterized be its frequent use of short hoots with more complex
hoots, along with a "quavering" opening and closing. These calls are one
of the traits used determining species differences among the gibbons.
Reproduction
Sexually they are similar to other gibbons. Gestation is seven months
long and pregnancies are usually of a single young. Young are nursed for
approximately two years, and full maturity comes at about 8 years. The
life expectancy of the Lar Gibbons in the wild is about 25 years.
Status
Lar Gibbons are threatened in various ways: they are sometimes hunted
for their meat, sometimes a parent is killed in order to capture young
animals for pets. The largest danger, however, is the loss of habitat.
With breathtaking speed the forests of Southeast Asia are cut down in
order to establish plantations, fields and settlements. National parks
and protected areas exist, but are often poorly supervised.
Subspecies
There are five subspecies of Lar Gibbon:
* Malaysian Lar Gibbon, Hylobates lar lar
* Carpenter's Lar Gibbon, Hylobates lar carpenteri
* Central Lar Gibbon, Hylobates lar entelloides
* Sumatran Lar Gibbon, Hylobates lar vestitus
* Yunnan Lar Gibbon, Hylobates lar yunnanensis (possibly extinct |
