The dental formula of the Javan langur is 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). This species has a sacculated stomach to assist in the breakdown of cellulose. The Javan langur has enlarged salivary glands to assist it in breaking down food. The palm print for the majority of individuals is of the simple loop type (Maryanto, 2000). The circumfacial hair is erect and forward-curled (Brandon-Jones, 1995). Females differ from males in having a pale, usually yellowish white, pubic patch (Brandon-Jones, 1995). Infants are orange in coloration (Rowe, 1996). Average body mass for the Javan langur is 7.1 kilograms (Rowe, 1996).
Groves (2001) describes two subspecies for the Javan langur, each having differing pelage colorations:
Trachypithecus auratus auratus: The common morph of this subspecies is a glossy black color with a slight brownish tinge on the ventrum, sideburns, and legs (Brandon-Jones, 1995; Groves, 2001). The hairs are light tipped on the arms, legs, head, flanks, and sometimes the back (Brandon-Jones, 1995; Groves, 2001). There is a rarer morph to this subspecies that is a deep orange color that becomes more yellowish on the limbs, hair around ears, and the ventrum (Brandon-Jones, 1995; Groves, 2001). The dorsal side hairs have a black tinge in this rarer morph (Brandon-Jones, 1995; Groves, 2001). The skin of the face, palms, and soles are black in the common morph and depigmented or freckled in the deep orange morph (Brandon-Jones, 1995; Groves, 2001).
Trachypithecus auratus mauritius: The pelage coloration of this subspecies is glossy black with a very slight brownish tinge on the ventrum, sideburns, and legs (Brandon-Jones, 1995; Groves, 2001).
Brandon-Jones (1995) describes an additional subspecies:
Trachypithecus auratus ebenus: The overall pelage coloration of this subspecies is glossy black, where the hairs tend to be brownish at the base (Brandon-Jones, 1995). The hair around the nipples and the throat are blackish brown in color (Brandon-Jones, 1995). On the chin, along the upper lip, and between the nostrils the hairs are colored black or black with yellow terminal bands with sparse intermingled yellow hairs (Brandon-Jones, 1995). Between the nostrils and the upper lip there is a patch of short, very fine whitish hairs (Brandon-Jones, 1995). On the dorsal side of the hands and feet, sparse white and yellow hairs intermingle with black colored hairs (Brandon-Jones, 1995). The pubic patch that females of this species have differs in this subspecies in that it starts out as orange at the vulva and grades towards a whitish color (Brandon-Jones, 1995).
Maryanto (2000), based on the palm and sole prints, suggests that there are not any subspecies to this species because the prints to do not show any clinal variation amongst the east, west, and central populations.
The Javan langur is found on the island of Java and the smaller islands of Bali and Lombok, Indonesia (Weitzel and Groves, 1985). Brandon-Jones (1995) describes a possible new subspecies from Indochina. In Pangandaran Nature Reserve, this species lives in small, dense groups, on the east side of the park, avoiding the teak plantations (Watanabe et al., 1996). However, Kool (1986) found that in the same reserve a group lived in a mixed lowland forest of secondary growth/ Tectonia grandis, Swietenia macrophylla, and Acacia auriculiformis plantation. The Javan langur was found to be rather common on Mt. Prahu, Indonesia (Nijman and van Balen, 1998). This species has been found to occur in primary and secondary forests, both in the interior and on the edge (Nijman and van Balen, 1998; Gurmaya et al., 1994). In Ujung Kulon National Park, Java, this species was found in all forest strata levels except the ground (Gurmaya et al., 1994).
Trachypithecus auratus auratus: The red morph of this subspecies has a restricted distribution between Blitar, Ijen, and Pugeran, Java (Groves, 2001). The more common morph is found in eastern Java, west to Gunung Ujungtebu (Brnadon-Jones, 1995).
Trachypithecus auratus mauritius: This subspecies has a restricted distribution in west Java to the north coast from Jakarta, inland to Bogor, Cisalak, and Jasinga, southwest to Ujung Kulon, then along the south coast to Cikaso or Ciwangi (Groves, 2001).
Trachypithecus auratus ebenus: This subspecies may only be found near Lai Chau, Vietnam, or from the Fan Si Pan mountain chain (Brandon-Jones, 1995).
The diet of the Javan langur consists of leaves (immature and mature), fruit (ripe and unripe), flowers, flower buds, and insect larvae (Kool, 1993). Kool (1992, 1993) found that half of the dietary intake for the subspecies T. auratus sondaicus consisted of protein-rich leaves. Leaves selected for consumption had a lower fibre content, thus having a higher degree of digestibility (Kool, 1992). Young leaves of the teak tree, Tectona grandis, are an important food source for this species when favored foods are scarce (Kool, 1993, 1991). The midrib of the leaf of the teak tree is the preferred part consumed, where an individual will bend the leaf in half (from apical tip to base), holding it with one or two hands while stripping and chewing it (Kool, 1993). Kool (1993) found that 27 to 37% of the diet of the Javan langur at Pangandaran Nature Reserve was fruit, with 15 to 27% of the diet unripe fruit and 10 to 12% of the diet ripe fruit. Fruits consumed tend to have higher amounts of condensed tannins and total phenolics than leaves consumed (Kool, 1992). Tannins may be useful in the diet because they may reduce acidosis of the stomach by slowing down the rate of fermentation (Goltenboth 1976; Davies et al., 1988; Kool, 1992). A considerable part of the diet of the subpsecies T. auratus sondaicus was found to include fruits that were ripe, and ripe fruits can cause acidosis in colobines (Goltenboth, 1976; Kool, 1992). Fruits tend to be eaten for their seeds (Kool, 1993). Watanabe et al. (1996) studying the Javan langur in the Pangandaran Nature Reserve found that when tourists (Humans Homo sapiens) tried to give food to the langurs that they would not accept the food. At Pangandaran Nature Reserve Kool (1993) found that important food tree species were Ficus sinuata, Ficus sumatrana, and Vitex pinnata. Brotoisworo and Dirgayusa (1991) found that one group at Pangandaran Nature Reserve fed on soil. Kool (1993) found that at Pangandaran Nature Reserve monthly variation in diet of when specific food were eaten varied amongst differed groups, where one group consumed fruits more significantly in July, August, September, January, and February and another groups fruit was consumed more in November and December. Groups will feed simultaneously on the same food source (Kool, 1993). Individuals of the group will also eat when the rest of the group is resting or traveling (Kool, 1993). Brotoisworo and Dirgayusa (1991) found that adult males fed less frequently as compared to other group adults and subadults.
The Javan langur is a diurnal and an arboreal species. The average group size for this species is around seven individuals (V. Nijman, unpubl. data; cited in Nijman and van Balen, 1998). Kool (1991) found that groups ranged in size from 6-21 individuals with one or two adult males in the group. On Lombok Island, Indonesia, group sizes were found to be larger in secondary and monsoon forests than in tropical forests (Supriatna et al., 1986).
A major predator of the Javan langur is humans who hunt this species for commercial and food purposes (Djuwantoko, 1994).
The Javan langur moves through the forest quadrupedally (Rowe, 1996).
The Javan langur lives in social groups of one or two adult males (Kool, 1991). Groups on Lombok Island were found to only have one adult male (Supriatna et al., 1986). Males disperse from their natal group and will travel solitarily or in all-male groups (Kool, 1989; Bennett and Davies, 1994; Rowe, 1996). Mengantara and Dirgayusa (1994) found that males tend to maintain close proximity with other group males, females maintain close proximity with other females, the dominant group male with all group members. Adult females will engage in aggressive encounters with adult females from other groups (Mengantara and Dirgayusa, 1994). Females will care for infants from other females (allo-mothering) (Kool, 1989; Bennett and Davies, 1994; Rowe, 1996).
VOCAL COMMUNICATION: alarm call: This call sounds like "ghek-ghok-ghek-ghok-" (Gurmaya et al., 1994).
The Javan langur gives birth to one offspring at a time.
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