AZA - Gibbons Fact Sheet

Gibbons Fact Sheet (5/1/94)
Gibbons (Hylobates ssp.)
Description: Gibbons are perhaps the most conspicuous animals in
Southeast Asian rainforests. Their songs are described as some of the
finest music ever uttered by a wild land mammal and their remarkable
power and grace in swinging through their tall tree habitat is unparalleled.
To many naturalists, gibbons are the voice and soul of the forest, an
observation also held by indigenous peoples who have shared the same
forests for centuries.
Because of their small body size, gibbons are termed lesser apes. Their
arms are relatively longer than their legs, adapting them to suspensory
locomotion--or brachiation-- which allows rapid movement through the
forest canopy and access to preferred foods. Gibbons come in many
different combinations of color, including jet black, silvery, rufus or
cinnamon; some species' colors vary with gender while other species
change color as they mature.
Gibbons in North American institutions are primarily represented by three
species. The siamang (Hylobates syndactylus) is the largest and both
sexes are all black but the male can be distinguished by a conspicuous
inflatable throat sac used for loud vocalizations. The white-handed gibbon
(H. lar) varies widely in appearance from area to area and can be either
black or buff colored; it can be distinguished by its white hands and feet.
The white-cheeked gibbon (H. concolor), also called the black gibbon, has
black males sporting white or reddish cheek patches while females are
buff or golden with black patches. Young change color as they mature
(males once, females twice).
Range: Gibbons are found throughout Southeast Asia from Assam in
northeast India across Indochina, north into southern China and south
throughout most of Indonesia. Specifically, the siamang is found on the
Malaysian peninsula and Sumatra. The white-cheeked gibbon is found in
Laos, Vietnam and southern China and the white-handed gibbon is found
in Thailand, the Malaysian peninsula and the northern third of Sumatra.
Habitat: Gibbons spend their entire lives in the tall trees of tropical
rainforests.
Diet: Gibbons are frugivores, feeding on small, but scattered fruits, young
leaves and, with some species, a few invertebrates. Differences in diet

elate to differences in habitat and food availability. Otherwise, gibbon
show a similar preference for fleshy, sugary fruit and figs.
Social Organization: Gibbons are unique among apes, and even among
Old World monkeys, in keeping strictly defended stable territories which
they live within at all times. Gibbons also come close to the ideal of
"mating for life." Each gibbon pair regularly advertises its territory by loud
singing accompanied by spectacular gymnastics--a show of force. The
female's great call dominates the half-hour morning bout of singing, and it
is punctuated by the male's shorter phrases. These songs are consistent
throughout the range for each species, but subtle differences characterize
individuals. Territorial singing of the family broadcasts precise information
on the species and sex of individuals, the area occupied by the parents
and the presence of a sub-adult ready to form a new pair.
Conservation Status: The IUCN Red List of Threatened Animals curently
lists the Javan gibbon (H. moloch) and the Mentawai Islands gibbon (H.
klossii) as endangered; the white-cheeked gibbon, the hoolock gibbon (H.
hoolock) and the pileated gibbon (H. pileatus) are listed as vulnerable. The
U.S. Fish & Wildlife Service lists all nine gibbon species as endangered
and they are also under Appendix I protection of CITES. Most recently, the
IUCN/CBSG Primate Working Group recognized 23 (possibly 26) subspecies
among the nine species, placing the pileated, the Javan, the
Mentawai Islands and all five white-cheeked subspecies as critical.
Threats to Survival: Reduction of the tropical rainforest is the primary
threat to gibbons. Poaching for food or capturing young gibbons for the pet
trade is a secondary, but sometimes equally serious threat. The numbers
of all gibbons in Asia have decreased rapidly in the past fifteen years.
Zoo Programs - SSP: The Gibbons SSP is still under going planning and
organization. At the inaugural meeting in 1990 the propagation group
recommended the following plan based upon IUCN Priority Status and
IUCN/Primate Specialist Group and IUCN/CBSG recommendations. a.)
Because of their threatened or endangered status, the Javan, hoolock and
Mentawi Islands gibbon species should be placed in captive breeding
programs meeting necessary criteria, when sufficient numbers of
individuals of each become available. (Possibly in North America or other
regional programs.) b.) The agile (H. agilis) and the gray gibbon (H.
muelleri) have a low priority for conservation and are not to be placed in a
captive breeding program at this time. c.) Because the white-cheeked
gibbon is endangered and a reasonable number of individuals are already
held in North American facilities, expansion of its numbers through
breeding has been recommended. d.) The pileated gibbon should be
placed in a global breeding program, since it is endangered but only low
numbers are held in North America. e.) The siamang and white-handed

gibbon have low conservation priority and their numbers in institutions are
to be contained, allowing more space for other gibbon species. Also, there
is to be a complete cessation of breeding until a molecular genetic
analysis is performed.
As of April 1995, there are about 150 siamangs, 50 white-cheeked
gibbons and 230 white-handed gibbons in North American zoological
facilities.
Conservation: One on the Gibbon SSP's first tasks is to tackle some
long-standing questions about the biological relevance of existing subspecies.
To effectively design and implement appropriate management
plans, the SSP must be able to recognize and divide gibbons into
evolutionarily significant units. This will allow the SSP to take action to
prevent undesirable hybridization between populations of different genetic
make-up. A number of specific research questions have been identified,
along with potential researchers capable of resolving these questions
within one to two years.
In situ conservation programs are not meeting the urgent need for action.
Two species, the Javan and pileated gibbon, are listed as critical; yet, no
conservation program exists for them, either for the Mentawai Islands
gibbon on the southern most island of Pagai, west Sumatra, Indonesia;
there are also plans to improve an established reserve on the northern
island of Siberut. Another release back into forested areas depleted of
gibbons is under discussion in Thailand.
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©2000 American Zoo and Aquarium Association