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The lutungs are a group of Old World monkeys and make up the entirety of the genus Trachypithecus. Their range is split into two parts; one part is much of southeast Asia (northeast India, southern China, Borneo, Thailand, Java and Bali), the other part is extreme southern India and Sri Lanka. The greater part of India has lutungs. Most of the species in this genus can be referred to as lutungs, as langurs, or as leaf monkeys.
The recent phylogenetic relationships confirmed that Purple-faced Leaf Monkey should be classify within the genus Semnopithecus, not with Trachypithecus. Mitochondrial genome allows no resolution of the phylogenetic relationships among langur genera, but five retroposon integrations were detected which link Trachypithecus and Semnopithecus. According to Y chromosomal data and a 573 bp fragment of the mitochondrial cytochrome b gene, a common origin of the species groups T. cristatus, T. obscurus and T. francoisi and their reciprocal monophyly is supported, which is also underpinned by an orthologous retroposon insertion. T. vetulus clusters within Semnopithecus, which is confirmed by two retroposon integrations. Moreover, this species group is paraphyletic, with T. vetulus forming a clade with the Sri Lankan, and T. johnii with the South Indian form of S. entellus. Incongruence between gene trees was detected for T. pileatus, in that Y chromosomal data link it with T. cristatus, T. obscurus and T. francoisi, whereas mitochondrial data affiliates it with the Semnopithecus clade.
Although all of them are morphologically similar, T. vetulus was sometimes separated in its own genus Kasi , and recent mitochondrial sequence data indicate a closer affiliation of T. vetulus and T. pileatus to Semnopithecus than to Trachypithecus. Accordingly, the two T. vetulus members were recognized as species of Semnopithecus. In contrast to Trachypithecus, the genus Semnopithecusis restricted to the Indian subcontinent.
Lutungs have a rather slim build with a long tail. The fur coloring varies depending upon species from black and grey to orange yellow. Many species have skin designs and a brighter lower surface, the hair on the head is often compared to a hood. Their arms are very short in comparison to the feet and their thumbs are also somewhat shorter. The inner surfaces of the hands and feet are hairless so that their fur doesn't get caught when reaching into branches. These animals reach a length of 40 to 80 cm and a weight of 5 to 15 kg, with males generally larger than females. A bulge over the eyes and other details, primarily in the head, differentiate it from the surilis.
Habitat and behaviour
Lutungs live in the forests, often preferring rain forests although occasionally they are also found in secluded mountain forests. They spend the largest part of the day in the trees, where they crawl along the branches on all fours, although they can also jump well from tree to tree. They are diurnal, although more active in the early mornings and the afternoon.
They live in groups of 5 to 20 animals, mostly in harems, i.e. a single male with several females. Young males must leave their birth group when fully mature, often forming bachelor groups. If a new male takes over a harem, defeating and scaring off the harem leader, it often kills the children of the group. Lutungs are territorial, with loud shouting to defend their territory from other lutung interlopers, resorting to force if the outsiders aren't scared off. They have a common repertoire of sounds with which they warn group members. Also, mutual grooming plays an important role.
Lutungs are herbivores, primarily eating leaves, fruits and buds. In order to digest the hard leaves, they developed a multichambered stomach.
Rarely twins, a typical single birth comes after a seven month gestation period. Newborns usually have a golden-yellow fur. The mother shares responsibilities of rearing the young with the other females ("aunties") of the harem. They hand the young around, play with it, carry it and cuddle it, while the mother searches for food. If the mother dies, another female adopts the young animal. Lutungs are weaned in the latter half of their first year, and reach full maturity at 4 to 5 years. The life expectancy is estimated at 20 years.
- Genus Trachypithecus
- T. vetulus group
- T. cristatus group
- T. obscurus group
- T. pileatus group
- T. francoisi group
Genetic analysis indicates that the ancestors of the modern species of lutung first differentiated from one another a little over 3 million years ago, during the late Pliocene. The various species alive today then diverged during the Pleistocene, presumably driven by habitat changes during the Ice Ages. The oldest fossils clearly identified as belonging to the genus date from the middle Pleistocene of Vietnam and Laos; later fossils are also known from Thailand, Java, and Sumatra. The closest living relatives of the lutungs are probably either the gray langurs or the surili, although the exact relationships remain unclear, possibly due to hybridisation between these genera during the course of their recent evolutionary history.
- Harding, L.E. (2010). "Trachypithecus cristatus (Primates: Cercopithecidae)". Mammalian Species 42 (1): 149–165. doi:10.1644/862.1.
- Roos, C. et al. (2008). "Mitochondrial phylogeny, taxonomy and biogeography of the silvered langur species group (Trachypithecus cristatus)". Molecular Phylogenetics and Evolution 47 (2): 629–636. doi:10.1016/j.ympev.2008.03.006. PMID 18406631.