What are the gibbons?
- Gibbons are apes: The gibbons (family Hylobatidae)
- together with the great apes (family Hominidae) - make up the superfamily of the
apes (Hominoidea).
- The gibbons are also known as the small apes.
- With 12 species, the gibbons comprise the largest
group of the apes.
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Habitat adaptation
- The gibbons live in the evergreen tropical rainforests
of Southeast Asia.
- They are adapted to life in the treetops.
- Gibbons eat mainly fruit - in addition,
they eat leaves, flowers and insects.
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Behaviour
- Gibbons live in small family groups (monogamy).
The monogamous social structure is unusual - it occurs in only about 3% of mammals.
- Groups usually consist of an adult pair and their
immature offspring. The group size is 2-6 individuals.
- Each group has a territory of 20-45 hectares,
which is aggressively defended from other groups.
- Gibbon pair-bonds last for many years.
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Locomotion
- Gibbons move mainly by swinging by their arms (brachiation),
but they can also walk on two legs (bipedalism).
- The spectacular brachiation of the gibbons makes
them the most acrobatic of all apes. When in a hurry, gibbons seem to be virtually
flying through the treetops.
- On branches and the ground, gibbons walk on two
legs. Therefore, gibbons are possibly the best primate model for the evolution of
bipedalism in humans.
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Anatomy
- Gibbons exhibit numerous anatomical specialisations
which are linked to their unusual locomotion.
- For instance, their arms are particularly
elongated. Relative to body size, gibbons have the longest arms of all primates.
- Gibbons weigh only 5-12 kg (there is variation
between the species) and are therefore the smallest of the apes. Their light build
makes enables them to collect fruit from thin branches.
- Like the other apes, gibbons do not have a tail.
 Click here to see a short video
clip of wild gibbons moving around in the tree crowns (Hylobates muelleri)
(video: Yoichi Inoue).
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Systematics
There are four main groups of gibbons. These
are thought to represent different genera, which are as distant to each other as
humans and chimpanzees.
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Siamangs
Symphalangus
1 species
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Crested gibbons
Nomascus
4 species
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Hoolocks
Hoolock
1 species
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Lar or dwarf gibbons
Hylobates
6 species
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Distribution
- Gibbons have a large range that extends over almost
all of Southeast Asia.
- Gibbons are distributed over most of Indo-Burma
and Sundaland. These are two of earth's biologically richest and most endangered
terrestrial ecoregions.
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Gibbon songs
- Early in the morning, gibbons produce spectacular
songs, which can be heard as far as 1-2 km away.
- Singing is very rare in mammals. Gibbons produce
the most complex songs of all land mammals.
- Song-bouts usually last about 10-30 mins.
- Gibbon songs reveal the singer's species, sex and
individual identity.
- The songs probably serve to mark territorial boundaries
and find partners.
Click here to see a video excerpt
from a male song of the white-cheeked crested gibbon (Nomascus leucogenys)
(video: Thomas Geissmann).
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Duetting
- Mated gibbons usually sing together in well-coordinated
duets.
- Duetting probably serves to advertise or strengthen
the pair bond.
- Gibbon songs are probably the best model for the
evolution of human music, since both are derived from the same, genetically
determined call type.
Click here to see a video excerpt from a duet song of the siamang (Symphalangus
syndactylus) (video: Andrea About).
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Self recognition
- So far, the cognitive abilities of the gibbons
have hardly been studied.
- Gibbons can recognise themselves in the mirror,
which is generally taken to indicate self-consciousness. Gibbons share this
ability only with humans and other great apes.
Figure: This gibbon examines the inside of his mouth in the mirror (left) and
makes unusual body positions (right). He is clearly interested in observing this
in the reflection (photos: Maria Ujhelyi).
Reference: Ujhelyi, M.; Merker, B.; Buk, P. and Geissmann, T. (2000) Journal
of Comparative Psychology 114, pp. 253-262.
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Conservation
- Gibbons not only include the most endangered apes
but also the most endangered primate species of the world. Several gibbon species
are threatened by imminent extinction in the very near future.
- The plight of the small apes receives virtually
no media coverage. The gibbons are the true neglected apes and need our help.
Figure: Hunted pileated gibbon (Hylobates pileatus) in Cambodia (photo:
Ian Baird).
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Our knowledge
- Although the gibbons are the most species-rich
group of the apes, so far they have been hardly studied. Gibbons are the most
under-researched of the apes.
- We know nearly nothing about their social life
and their cognitive capacities.
- Several species have never been studied in the
wild, have never been filmed, and have never been bred in captivity.
- Gibbons are highly important in understanding the
evolution of humans and apes.
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Want to learn more?
There is more on the Internet.
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Acknowledgements
I thank Lucy Birkett for her help in translating
this text.
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