The dental formula of the golden 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 golden langur has enlarged salivary glands to assist it in breaking down food. The average body mass for adult males is 10.8 kilograms and for adult females it is 9.5 kilograms (Fleagle, 1999). The length of the head and body ranges from 50-75 centimeters, and the length of the tail ranges from 70-100 centimeters (Gurung and Singh, 1996). The pelage color ranges from golden to creamy white and changes to a red color with the former applying to the summer and the latter applying to the winter and breeding season (Khajuria, 1977). On the crown there is an ill-defined whorl of hair that may protect the eyes and face from glare (Khajuria, 1977). Around the ears long whiskers may be found which may protect the ears from rainwater during the monsoon season (Khajuria, 1977). The newborn pelage is an apricot color.
The golden langur is found in the countries of Bhutan and India. There has been one published report of a golden langur sighting in central Nepal at 7800 feet across the Modi Khola valley, but it may have a stray or isolated case (Varley, 1985; Choudhury, 1992). In western Assam, India the golden langur has been observed at Jamduar, Raimona, Chakrasila forest, Bismurei, Ultapani, Karigaon, Haltugaon, Nayakgaon, Kachugaon, Chaprakata, and Khokarpara (Mukherjee, 1995). Two groups were translocated in Assam, India one to Sepahijala and the other to a small island in the Brahmaputra river opposite Guwahati (Mukherjee and Southwick, 1996/1997; Mukherjee, 2000/2001). This species lives in evergreen and deciduous tropical forests. At Jamduar and Raimona, India, the golden langur lives in tropical, mixed deciduous or semi-deciduous, semi-moist, and Sal forest (Khajuria, 1977).
Gupta (2002, 1998) found in Tripura, India, the golden langur had a diet that consisted of young and mature leaves, ripe and unripe fruits, and seeds, with most of the feeding spend on young leaves (41.4%). Seeds and mature leaves were the next most popular food in the diet (Gupta, 2002). Subba (1989), however, found that in Manas National Park, Bhutan, this species prefers fruits and buds to leaves. Mukherjee (2000/2001) also found that leaves are the most important food item for this species in areas of western Assam. Gee (1961; cited in Subba, 1989) found that the diet of the golden langur consisted mostly of flush, tender leaves, buds, and fruits. Khajuria (1977) found that the diet of this species consisted mostly of leaves and buds of Bombax ceilia, Bauhina, Ficus, Acacia, and Terminalia species. A group introduced to Umananda Island in the river Brahmaputra was found to have a diet consisting of 74% leaves, 9% fruits, and 5% flowers (Biswas et al., 1996). At Manas National Park the fruits of the species Bombax simul, Duagbanga indica, mulberry, and the leaves of Bauhenia sp. were found to be foraged on, and these species are not found in any other part of the golden langur's range (Subba, 1989; Subba and Santiapillai, 1989). Wayre (1968; cited in Khajuria, 1977) observed a favorite food item was the cherry-like bud of the Balu tree, Dilleria pentagyna. Khajuria (1977) found that during the hot season the golden langur would take water from water holes and during the other seasons enough water is found on foliage for the golden langur to drink. Gee (1961; cited in Khajuria, 1977) found that this species drank and licked salty earth in February.
Gupta (2002) found that the golden langur preferred to eat plantation species, most of which came from the Leguminosae and Moraceae families. However Khajuria (1977) and Mukherjee and Saha (1974) noted that this species has an inability to raid crops. In Tripura feeding was found to account for 45.5% of the activity time (Gupta, 2002). Subba (1989) found that in Manas National Park, feeding for the golden langur starts early in the day, going on until mid-day with being interrupted by rest periods.
In Manas National Park group sizes ranges from 2 to 12 individuals (Santiapillai, 1988; cited in Subba, 1989). Mohnot (1980; cited in Subba and Santiapillai, 1989) found that in Manas National Park the groups ranged in size from 4-40 individuals. At Jamduar and Raimona, India, Khajuria (1977) found that group sizes ranged from 7-15 individuals. A census in western Assam of 130 groups found that the average group size was 8.2 individuals (Srivastava et al., 2001). Srivastava et al. (1998) found that groups living in degraded habitats lived in larger groups and have a higher population density, but have lower birth rates.
This is a diurnal and an arboreal species (Khajuria, 1977). In the Chakrashila Wildlife Sanctuary, Assam, India, the activity budget of the golden langur was found to consist of 54.75% resting, 29.26% feeding, 8.59% traveling, 3.93% monitoring, 2.03% playing, and 1.45% grooming (198 hours of observation) (Chetry et al., 2002). A group introduced on to Umananda Island in the river Brahmaputra had a daily activity budget of spending 30% of the time feeding, 41% of the time resting, 19% of the time moving, and 6% of the time grooming (Biswas et al., 1996). This species will sleep in high trees, 21 to 24 meters from ground level (Mukherjee and Saha, 1974).
Daily activity consists first of waking before the sun rises above the horizon and remaining in the tree slept in for a period of time feeding, playing, resting, and moving from branch to another (Mukherjee and Saha, 1974). During the winter, individuals will orient themselves towards the sun to sunbath before moving to feeding trees (Mukherjee, 2000/2001). When the group starts to move out of the sleeping tree, they move slowly and silently, often moving in a single file (Mukherjee and Saha, 1974; Mukherjee, 2000/2001). Movement is controlled by the dominant male who will lead the group (Mukherjee and Saha, 1974). When crossing roads, the group will find trees that are close together that form a continuous canopy, never descending to the ground to cross (Mukherjee and Saha, 1974). Adult males will allow the rest of group to flee first when presented with a potential predator (Mukherjee and Saha, 1974). This species, like other primates, tends to feed in the morning and in the evening, resting during the mid-day heat (Mukherjee and Saha, 1974). The mid-day rests tend to occur on large trees with thick foliage during the summer, and on the open parts of the trees exposed to the most sunlight during the winter (Mukherjee, 2000/2001). Resting occurs for a shorter period of time in winter than in summer (Mukherjee, 2000/2001). During the mid-day rests activities such as social grooming and social play will occur (Mukherjee, 2000/2001). Mukherjee and Saha (1974) found that the golden langur feeds at an average height of 15 to 21 meters, occasionally coming down to lower branches. When feeding the group will stay in close contact, either remaining in the same tree or a neighboring tree (Mukherjee and Saha, 1974). Females with infants and juveniles will feed for a longer period of time as compared to other group members (Mukherjee and Saha, 1974). Groups will move to their sleeping trees around evening, and the sleeping trees are generally different from night to night (Mukherjee and Saha, 1974). Group members will sleep in the same tree, but huddling in adults has not been observed (Mukherjee and Saha, 1974).
Potential predators of the golden langur include tigers (Panthera tigris), leopards (Panthera pardus), clouded leopards (Neofelis nebulosa), and humans (Homo sapiens) (Khajuria, 1977).
The golden langur moves through the forest quadrupedally (Fleagle, 1988). This species will leap from tree to tree when moving quickly, as when alarmed (Mukherjee and Saha, 1974). When leaping, this species will take off with the hindlimbs and land on the fore and hindlimbs (Gurung and Singh, 1996).
The golden langur can have groups that are comprised of either one or two adult males (Biswas, 2002; Subba, 1989; Mukherjee and Saha, 1974). There was one group found with 4 adult males (Mukherjee and Saha, 1974). An all-male group consisting of three adult males and two subadult males has been observed (Mukherjee and Saha, 1974). Males will disperse from their natal groups (Mukherjee, 1978). Mukherjee and Saha (1974) found that in Jamduar and Raimona, India, out of 125 individuals counted, 16% were adult males, 39.2% adult females, 20.8% juveniles, and 24.0% infants. Of the adult individuals at Jamduar and Raimona, 28.99% were males and 71.01% were females (Mukherjee and Saha, 1974). Some groups have home ranges that overlap, and aggression was found to occur during the birth season and the peak breeding season contrasting with a more peaceful coexistence at the end of the birth season and the start of the copulatory phase (Biswas, 2002). Some groups will shift their home range, avoiding conflict with other groups, so as to forage for food more easily and be able to better care for infants (Biswas, 2002).
At Tripura the golden langur is sympatric with the capped langur, Trachypithecus pileatus, and resource-use partitioning exists where the two species will forage on different food species for different plant parts (Gupta, 2002). The capped langur has also recently penetrated into the Royal Manas National Park by way of a bridge (Wangchuk et al., 2001). A mixed group of golden langurs and capped langurs has been observed there, with some of the individuals having coat colors intermediate between the two species (Wangchuk et al., 2001). This species is also sympatric with hanuman langurs in Bhutan, where the hanuman langurs, Semnopithecus entellus, were able to cross the Sankosh river because of the construction of a bridge (Wangchuk, 1995/1996). Wangchuk (1995/1996) believes the two species are interbreeding in the Tsirang area. At Sepahijala, India, the golden langur is sympatric with capped langurs, Phayre's langurs, Trachypithecus phayrei, rhesus macaques, Macaca mulatta, pigtail macaques, Macaca nemestrina, and the slow loris, Nycticebus coucang (Mukherjee, 2000/2001). The three langur species are described as being peaceful towards one another, only issuing mild threats when coming close in contact during foraging or moving (Mukherjee, 2000/2001). Assamese, Macaca assamensis, and rhesus macaques will displace the golden langur from feeding sites (Mukherjee, 1978).
Social play is mainly restricted to juveniles, with infants occasionally joining in (Mukherjee and Saha, 1974). Social play includes the activities of: chasing, wrestling, climbing, running, and jumping on the thick branches of trees (Mukherjee and Saha, 1974). Mukherjee and Saha (1974) found that play in golden langur is only found to occur in trees.
VOCAL COMMUNICATION: alarm call: This is a short, low pitched vocalization that sounds like "nauk-nauk..." (Mukherjee and Saha, 1974). This call is emitted by males with mouths closed (Mukherjee and Saha, 1974). Usually the adult male will emit this until other group members can get to safety during a disturbance (Mukherjee and Saha, 1974).
barking alarm call: This is a high pitched vocalization that sounds like "aeke-ke-aeke-ke..." (Mukherjee and Saha, 1974). This call is emitted in quick succession by adult males by opening the mouth widely (Mukherjee and Saha, 1974). This call is emitted when males are frightened (Mukherjee and Saha, 1974).
infant screech: This is given when infants are afraid, and this call sounds like similar notes given by rhesus macaques (Mukherjee and Saha, 1974).
TACTILE COMMUNICATION: social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals. This behavior is rare in the golden langur, and it tends to occur during the mid-day rest period (Mukherjee, 2000/2001).
The golden langur gives birth to a single offspring. The gestation period for this species is 6 months (Subba, 1989; Subba and Santiapillai, 1989). At Manas National Park, Bhutan, the breeding season in from January-February (Subba, 1989; Subba and Santiapillai, 1989).
During the first month of life, a newborn golden langur will devote 55.05% of its time to sleeping and sitting, 21.61% to pulling and pushing, and 13.76% to suckling (Medhi and Bhattacharjee, 2002). The newborn is also completely dependent on its mother, and the mother and allomother will support the newborn during rest and transport (Medhi and Bhattacharjee, 2002; Mukherjee and Saha, 1974).
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