The lar gibbon (Hylobates lar), also known as the white-handed gibbon, is an endangered primate in the gibbon family, Hylobatidae. It is one of the better-known gibbons and is often kept in captivity. The fur coloring of the lar gibbon varies from black and dark-brown to light-brown, sandy colors. The hands and feet are white-colored, likewise a ring of white hair surrounds the black face. Both males and females can be all color variants, and the sexes also hardly differ in size. Gibbons are true brachiators, propelling themselves through the forest by swinging under the branches using their arms. 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. As with all apes, the number of caudal vertebrae has been reduced drastically, resulting in the loss of a functional tail. Gibbons have tough, bony padding on their buttocks, known as the ischial callosities, or sitting pads. Lar gibbons have the greatest north-south range of any of the gibbon species. They are found in Indonesia, Laos, Malaysia, Myanmar and Thailand. Their range historically extended from southwest China to Thailand and Burma south to the whole Malay Peninsula in primary and secondary tropical rain forests. It is also present in the northwest portion of the island of Sumatra. In recent decades, especially, the continental range has been reduced and fragmented. Lar gibbons are likely extinct in China, but if they still exist, they would only be found in southwest Yunnan, their former range. Lar gibbon are usually found in lowland dipterocarp forest, hill dipterocarp forest, and upper dipterocarp forest, including primary lowland and submontane rainforest, mixed deciduous bamboo forest, and seasonal evergreen forest. They are not usually found higher than 1200 meters above sea level. The gibbon genus is highly allopatric, usually separated by large rivers. As a result, their range extends through southern and eastern Myanmar, but only east of the Salween River. They are found through the Malay Peninsula. Lar gibbons also exist west of the Mekong River in northwestern Laos and northern Sumatra.