Reflecting this mode of locomotion, the white-handed gibbon has curved fingers, elongated hands, extremely long arms and relatively short legs, giving it an intermembral index of 129.7, one of the highest of the primates.

[7] As with all apes, the number of caudal vertebrae has been reduced drastically, resulting in the loss of a functional tail.

[9] Their range historically extended from southwest China to Thailand and Burma south to the whole Malay Peninsula in primary and secondary tropical rain forests.

), Thomas's langur (Presbytis thomasi), slow loris (Nycticebus coucang), and several macaques (Macaca spp.

[13] The lar gibbon is considered frugivorous with fruit constituting 50% of its diet, but leaves (29%) are a substantial part, with insects (13%) and flowers (9%) forming the remainder.

[14] During the summer months, when figs and leaves are less available, insect consumption increases twenty-fold relative to the winter.

The most noticeable characteristic of the dentition of Hylobates lar is the presence of large, dagger-like canines in both the upper and lower jaw.

Their social organization is dominated by monogamous family pairs, with one breeding male and one female along with their offspring.

Long-term studies conducted in Khao Yai National Park in Thailand suggest their mating system is somewhat flexible, incorporating extra-pair copulations, partner changes and polyandrous groupings.

Each morning, the family gathers on the edge of its territory and begins a "great call", a duet between the breeding pair.

In the presence of tiger, clouded leopard, crested serpent eagle and reticulated python songs were more likely to contain sharp wow elements than normal duets.

[23] Lar gibbons are threatened in various ways: they are sometimes hunted for their meat, sometimes a parent is killed to capture young animals for pets, but perhaps the most pervasive is the loss of habitat.