Kloss’s gibbon (Hylobates klossii)

Also known as: dwarf gibbon, Mentawai gibbon
French: Siamang De Kloss
Spanish: Siamang Enano
GenusHylobates (1)
Weight6 kg (2)

Kloss's gibbon is classified as Endangered (EN) on the IUCN Red List (1). Listed in Appendix I of CITES (3).

Both male and female Kloss’s gibbons (Hylobates klossii) have short, black hair throughout their lives. The chest is broad and the limbs are long (4), which aids in swinging from branch-to-branch, a form of locomotion known as ‘brachiation’ (5). The thumbs and big toes are also very long, and there is webbing between the digits of the hands and feet (4). There is a sac below the throat which is used to produce calls (5). The muzzle is relatively short, and the hair on the crown lies flat; in infants, however, this hair is erect (4).

Kloss's gibbon is found on North and South Pagi, Sipora and Siberut, islands in the Mentawai group, West Sumatra in Indonesia (2).

Kloss's gibbon inhabits tropical rainforest (2) and monsoon forest (5).

Kloss’s gibbon is an arboreal species, spending most of its time in the canopy. They are active in the day (2) and get around by swinging from branch-to-branch, their long hands forming perfect hooks for grasping the branches (5). They live in groups, consisting of a breeding pair and their offspring, with social grooming helping to maintain bonds (5). These groups defend a territory, with loud bouts of singing serving to proclaim ownership (2). Neighboroughing males chorus before dawn and females after dawn with a 50 second great call (6). As young males and females reach sexual maturity they will leave the family group, with the aim of finding a mate and establishing a new group (5). These gibbons feed mainly on fruit, but will also take flowers and some invertebrates to supplement the diet (5).

Males and females form monogamous pairs. A single young is produced after a gestation period of seven to eight months. There is typically a gap of two to three years between each birth (2).

The main threat facing these gibbons is habitat destruction and degradation caused by human activities in the area (1). Hunting is also a problem, which worsens as habitat destruction continues, as it allows greater access into the forest (2).

Kloss’s gibbon is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which prohibits international trade in this species (3).

For further information on gibbons:

Authenticated by Dr David J. Chivers, University of Cambridge.

  1. IUCN Red List (April, 2011)
  2. Animal Info (March, 2004)
  3. CITES (March, 2004)
  4. Gibbon Conservation Centre (March, 2004)
  5. Primate Behaviour (March, 2004)
  6. Chivers, D.J. (2005) Pers. comm.