Hylobates is one of the four genera of small apes commonly called gibbons. Members of this genus are native to forests in Southeast Asia and are among the most widespread of the gibbons. The group is usually said to contain six or seven species, depending on how populations are classified, and many individuals show a distinctive pale ring of fur around the face.
Physical characteristics
Hylobates species are small, tailless apes with long arms and slender bodies adapted for life in the forest canopy. They move primarily by brachiation — swinging hand-over-hand through branches — and possess highly mobile shoulder joints and long curved fingers. Unlike some other primates they lack a tail and have vocal sacs that amplify loud, far-carrying calls. Chromosome studies identify members of this genus as having 44 chromosomes, a diagnostic cytogenetic trait used in primate taxonomy.
Species and distribution
Different taxonomic treatments recognize from six to seven species in Hylobates. Commonly named members include the white-handed gibbon (Hylobates lar), the agile gibbon (H. agilis), Müller's gibbon (H. muelleri), the silvery or Javan gibbon (H. moloch), the pileated gibbon (H. pileatus) and Kloss's gibbon (H. klossii). For an overview of recognized taxa and regional differences see a species list. These gibbons occur across mainland Southeast Asia and several nearby islands, where each species occupies forested habitats of varying elevation.
Behavior, diet and social life
Hylobates live in small family groups that typically include a mated pair and their offspring; pair bonds are often long-lasting and territorial behavior is maintained through loud singing. Vocal duets between mates are used to advertise territory and strengthen bonds. Their diet is primarily frugivorous, supplemented with leaves, flowers and insects, and they play important roles as seed dispersers in tropical forests.
Conservation and notable facts
Many Hylobates species face threats from habitat loss, fragmentation and hunting. Because these apes require large areas of continuous canopy for efficient locomotion and foraging, forest clearance has serious impacts. Several populations are listed as vulnerable, endangered or critically endangered by conservation assessments. Hylobates are also significant in studies of primate communication, locomotion and the evolution of social systems among lesser apes; for general background on gibbon diversity consult resources on Hylobates.