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Hylobates agilisagile gibbon

By Jennifer Kuester

Geographic Range

Gibbons are found throughout the tropical rainforests of South and Southeast Asia. Agile gibbons, Hylobates agilis, are found in Thailand, Indonesia, and Malaysia.

Habitat

Hylobates agilis is found in the tropical rainforests of Thailand, Malaysia, and Indonesia. They live in the upper canopy of the forest, feeding on fruits, leaves, and insects. Members of Hylobates spend most of their lives in the trees, and rarely descend to the ground.

Physical Description

Lesser apes in the family Hylobatidae are generally small. The average weight of H. agilis is 5.4 kg for females and 5.8 kg for males. Agile gibbons come in a variety of different colors, including black, brown, light tan and reddish-brown. Both sexes have white eyebrows. Males and females can be easily distinguished by the white eyebrows and cheeks possessed by the males.

Gibbons lack tails. Hylobates agilis, like other gibbons, has extremely long arms and fingers. This adaptation aides in brachiation, the prnciple mean of locomotion for these animals. Brachiation consists of hanging from branches and swinging from tree to tree.

  • Sexual Dimorphism
  • male larger
  • Range mass
    4 to 6 kg
    8.81 to 13.22 lb

Reproduction

Hylobates agilis forms monogamous bonds. Mated pairs stay together until one of them dies.

Hylobates agilis becomes sexually mature around the age of 8 years. The gestation period is about seven months. These animals give birth to a single offspring per pregnancy, and a mated pair can produce five to six offspring during their reproductive lifetime. The interbirth interval for H. agilis is around forty months.

  • Breeding interval
    The interbirth period for H. agilis is around forty months.
  • Breeding season
    These animals do not have a strict breeding season.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Average gestation period
    7 months
  • Average age at sexual or reproductive maturity (female)
    8 years
  • Average age at sexual or reproductive maturity (male)
    8 years

Most female gibbons nurse and care for their offspring until the offspring are about two years old. Offspring remain with their parents until they reach sexual maturity, around eight years, they then disperse from their natal group.

Males also particpate in parental care in this monogamous species. Males groom offspring, and help to defend them.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

The reported lifespan in captivity for these lesser apes is 44 years. Wild animals probably do not live as long.

Behavior

The average group size for H. agilis is four individuals. The group usually consists of the male and female mated pair, an infant, and a juvenile.

Gibbons exhibit two unique forms of behavior: monogamy and "singing". When an individual H. agilis disperses from its natal group (when it has reached sexual maturity), it finds a mate that it will spend the rest of its life with. These monogamous bonds are important for raising young and for defending the pair's territory. Hylobates agilis defend a territory by "singing". In the early morning, great calls can be heard throughout the upper canopy. These singing bouts are often duets and are a way of claiming home territory. When singing is not enough to keep intruders away, both male and female gibbons will chase the intruder away.

Communication and Perception

As in all primates, communication in this species is complex and involved several different modalities.

As mentioned in the "Behavior" section, above, these animals are highly vocal, and use great call vocalizations to defend their territories from other mated pairs.

Tactile communication is also important, between mates, and between parents and their offspring. Tactile communication involves grooming, mating, play and sometimes aggression.

In addition to vocal and tactile forms of communication, these animals use facial expressions, gestures, and body postures to communicate with conspecifics.

  • Other Communication Modes
  • duets

Food Habits

Hylobates agilis consumes large amounts of fruits. Like other gibbons, these animals are primarily frugivorous. Agile gibbons have also been observed eating a variety of other foods, including leaves, flowers, and insects. Due to their active lifestyle, it is necessary for them to eat food rich in calories. Fruits have a high caloric content.

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • fruit
  • flowers

Predation

Details on predation in this species are not available. However, snakes and raptors are probably the greatest threats to these animals. Because of their highly arboreal lifestyle, many potential predators are not likely to have access to these animals.

Ecosystem Roles

As these animals are not likely to be an important source of food for other animals, their greatest role in the ecosystem is probably seed dispersal for the fruits they eat.

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Hylobates agilis is not an important economic resource for humans. These animals are sometimes hunted for food, and they are illegally captured for the pet trade. Poaching is a threat to H. agilis, for animals that are caught often die in transport from mishandling. Illegal poaching for meat and the pet trade are contributing factors in the declining numbers of H. agilis.

Economic Importance for Humans: Negative

There is no known negative economic effect of this species on humans.

Conservation Status

Hylobates agilis is listed by IUCN as an endangered species. Due to massive deforestation, their habitat is rapidly decreasing. This loss of habitat due to logging and agricultural demands is the main threat to gibbon species. Conservation measures have been taken, such as reserve game parks and breeding programs in zoos. Unfortunately, these measures are not enough, and more intense conservation efforts must be initiated in order to ensure the survival of these species.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Jennifer Kuester (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

"Agile Gibbon (Hylobates agilis)" (On-line). Accessed November 10, 1999 at http://members.tripod.com/uakari/hylobates_agilis.html.

Leighton, D. 1987. "Gibbons: Territoriality and Monogamy". Pp. 135-144 in B Smuts, D Cheney, R Seyfarth, R Wrangham, T Struhsaker, eds. Primate Societies. Chicago: University of Chicago Press.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Tuttle, R. 1986. Apes of the World. New Jersey: Noyes Publications.

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