Capped Langur (Trachypithecus pileatus)
This species has a sacculated stomach to assist in the breakdown of cellulose. The capped langur has enlarged salivary glands to assist it in breaking down food. The dental formula of the golden langur is 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). The tail of this species is longer than the head and body combined (Choudhury, 1989). The head and body length of adult males ranges from 68.4-70.0 centimeters and for adult females it ranges from 59.0-67.0 centimeters (Choudhury, 1989). The tail length for adult males ranges from 94.0-104.0 centimeters and for adult females it ranges from 78.0-90.0 centimeters (Choudhury, 1989). The capped langur has a pelage color of blackish or ashy gray on the dorsal side and dull-reddish to creamy-yellow and golden-yellow on the ventral side (Choudhury, 1989). The face is deep black with the crown blackish (Choudhury, 1989). The cheeks contrast with the rest of the face and the crown in being paler with a golden-reddish tinge (Choudhury, 1989). The ears, palms, and soles, are black in coloration (Choudhury, 1989). The hindquarters and the insides of the thighs are light cobalt blue, which is more prominent in males than females (Choudhury, 1989). The distal half of the tail is blackish (Choudhury, 1989). The pelage of infants is creamy-white with a golden tinge all over (Choudhury, 1989). The face, ears, palms, and soles of the infant are pinkish, with the face having a darker tinge (Choudhury, 1989). Juvenile capped langurs are a dull creamy-white all over with a light ash tinge on the back (Choudhury, 1989). The face, ears, palms, and soles are black in juveniles, but paler than in adults (Choudhury, 1989). Males can have a body mass ranging from 11.5-14.0, and the female body mass that ranges from 9.5-11.5 kilograms (Choudhury, 1989).
This species has four subspecies, each with distinct pelage features:
- Trachypithecus pileatus pileatus: The belly of this subspecies is colored yellowish gray-white and the chest and throat are whitish tinged with buff colored hairs (Groves, 2001). The dorsal color of this subspecies varies from iron gray to pale brown (Groves, 2001). The crown-cap is black and the tail is dark in coloration (Groves, 2001). The upper arms and legs are lighter than the hands and feet, which are colored like the dorsum (Groves, 2001). The whiskers are buffy-whitish (Groves, 2001).
- Trachypithecus pileatus durga: The dorsal side of this subspecies are a paler, slaty gray color, and the ventral side and the belly, whiskers, and throat are orange to gingery (Groves, 2001).
- Trachypithecus pileatus brahma: The dorsal side of this subspecies is dark gray that becomes a more fawn-gray on the lower flanks, rump, and legs (Groves, 2001). The belly is white, tinged with buff, and the chest and throat are white in coloration (Groves, 2001). The crown is not dark (Groves, 2001). The insides of the limbs are pale gray, and the hands, feet, and tail are black (Groves, 2001).
- Trachypithecus pileatus tenebricus: This subspecies is darker than the other subspecies, and is ashy black on the dorsal side (Groves, 2001). This subspecies has a black crown-cap defined behind a gray collar (Groves, 2001). The belly is whitish in the male and pale red in the female (Groves, 2001). The ventral side and the bases of the whiskers are yellowish orange in coloration (Groves, 2001). The rest of the whiskers are gray in color (Groves, 2001). The legs are gray (Groves, 2001).
The capped langur is found in eastern and central Bangladesh, Bhutan, northwestern Burma, and the northeastern Hill States of India. In Bangladesh this species is found most frequently in the Madhupur forest tract, Jamalpur and Mymensingh districts, and in the forest of Sylhet, Chittagong, Chittagong Hill Tracts and Cox's Bazar Divisions (Khan, 1981). In northeast India this species is found in the states of Assam, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, and Meghalaya (Choudhury, 1989). This species lives in evergreen, tropical wet deciduous, montane, and primary forests. In northeastern India, the capped langur is lives in tropical evergreen rainforests, semi-evergreen forests, tropical moist deciduous forests, subtropical broad-leaved hill forests, in stands of bamboo, and in plantations of teak (Tectona grandis), gamari (Gmelina arborea), and simul (Salmalia malabarica) (Choudhury, 1989, 1996; Raman et al., 1995). In Bangladesh this species lives in Sal, evergreen, and Sunderbans type forests (Khan and Ahsan, 1986).
This species has four subspecies each having differing ranges:
- Trachpithecus pileatus pileatus: This subspecies is found in Burma, India, and Bangladesh (Groves, 2001). In Burma it is found from the Chin Hills south to Mount Victoria (Groves, 2001). In India it occurs in the Khasi, Garo, Naga, and Jaintia Hills (Groves, 2001). This subspecies is also found in the Karbi and Plateau and Barail Range in Assam (Choudhury, 1997; cited in Groves, 2001). This subspecies occurs in altitudinal ranges from 600 to 3000 meters (Groves, 2001).
- Trachypithecus pileatus durga: This subspecies is found in India, in the northern ranges of Trachypithecus pileatus pileatus, but at lower altitudes (Groves, 2001). This subspecies occurs at Naga Hills, Lakhimpur, Golaghat, Cachar Hills, Samaguting, and Sibsagar (Groves, 2001).
- Trachypithecus pileatus brahma: This subspecies is only known from the Dafla Hills, north of the Brahmaputra River in Assam (Groves, 2001).
- Trachypithecus pileatus tenebricus: This subspecies is found in the countries of India and Bhutan in the Manas region (Groves, 2001). This subspecies occurs in altitudes from 100 up to 1000 meters (Groves, 2001).
The capped langur is a folivorous species, but fruit also is a major component of the diet. Choudhury (1989) found that in northeastern India, capped langurs mainly fed on young leaves of various trees, shrubs, and climbers, and on seeds and flowers. This species eats a large amount of mature leaves as well as immature leaves when they are available. Bark of tender twigs has been observed to be consumed by this species (Choudhury, 1989). Stanford (1987) found that in Madhupur National Park, Bangladesh, the fruits and leaves of two species, Albizzia procera and Spondias mangifera, accounted for 64% of the feeding time. Islam and Husain (1982) found that in Madhupur National Park mature and young leaves were consumed 61% of the time and flowers, fruit, and seeds were consumed 30% of the time. Gupta (1998, 1994) studying capped langurs at Sepahijala Wildlife Sanctuary, India, found that young leaves (59.1% of the time) were consumed the most, with Albizzia stipulata the most preferred plant. In Assam, Mukherjee (1978) found that in the month of January the diet of the capped langur focused on leaves of Lagerstroemia parviflora, fruits of Bridelia retusa, and the flowers of Salmalia malabarica. During the monsoon months, fruit is a major part of the diet. Groups will spend 36% of the time on feeding during winter months, but only 31-33% of the time on feeding during summer and monsoon months (Alfred et al., 1998). Capped langur groups will not defend food sources in their territory (Stanford, 1991a). Capped langurs have various methods of consuming food items: they can be picked, held in the hand, and then eaten or picked and placed straight into the mouth or eaten right off of the tree (Islam and Husain, 1982). When feeding, individuals will use the hands for manipulation, holding, and pulling, and the teeth will be used for gnawing (Islam and Husain, 1982). Capped langurs will drink from depressions in the forks of trees, such as Dillenia pentagyna or come down to the ground, although coming down to the ground is done rarely (Stanford, 1991d).
At Madhupur National Park, the diet of the capped langur was found to consist of leaves and leaf parts (66.8%), fruit (24.4%), seeds (9.3%), and flowers (7.0%) (Stanford, 1991b). Mature leaves and petioles accounted for 42.0% of the diet and young leaves accounted for 10.9% of the diet (Stanford, 1991b). Stanford (1991b) found that 35 species of trees, lianas, and vines comprised the diet of the capped langur, of which 22 species were sources of leaves, 11 species were sources of fruit, 7 species were sources of flowers, and 6 species were sources of seeds. Mature leaves were the staple food eaten most when young leaves and other food is unavailable, especially in the winter months, with a peak in November (65.1% of the diet) (Stanford, 1991b). Mature leaves are mostly eaten whole, but sometimes only the tender tip is consumed with the rest of the leaf being discarded (Stanford, 1991b). Young leaves were consumed most when available in March-April and in late September (Stanford, 1991b). The most important sources of leaves came from Wrightia tomentosa, Bauhinia variegata, and Adina cordifolia (Stanford, 1991b). Fruit is consumed most during the rainy season (May-September) where it can comprise almost 50% of the diet (Stanford, 1991b). Examples of fruit consumed include Ficus sp., Spondias mangifera, and Terminalia balerica, with Garruga pinnata and Miliusa vetulina being the two most important fruit species consumed during the rainy season (Stanford, 1991b). Capped langurs were found to consume fruits of Mallotus phillipensis and Litsaea polyantha only for their small seeds (Stanford, 1991b). Flowers were consumed during the flowering peaks of May and October, just before and after the monsoon season (Stanford, 1991b). During October the most important source of flowers came from the large yellow flowers of Malvesia spp. (Stanford, 1991b). Stanford (1991b) suggests that capped langurs prefer fruit over leaves when both are available.
Group sizes range from 2 to 15 individuals. In Madhupur National Park, Stanford (1987) found that the mean group size of the capped langur was 7.0 individuals with a range of 4-13. Islam and Husain (1982) found in Madhupur the average group size was 6.4 individuals. In the Tinsukia district of Assam, Choudhury (1995/1996) found group sizes ranged from 5-15 individuals. Mukherjee (1978) found in Assam that the average group size was 9.7 individuals. This is a diurnal and an arboreal species, although older individuals will move more on the ground and other individuals will come to the ground to forage for leaves of climbers (Stanford, 1989; Choudhury, 1989; Ahsan, 1994). In the winter groups studied at Sepahijala Wildlife Sanctuary devoted 36% of the time to feeding, 38% to resting, 17% to traveling, 2.92% to grooming, and 4.05% to playing (Alfred et al., 1998). In the summer and monsoon months, these same groups devoted 31-33% of the time to feeding, 43-44% to resting, 13-15% to traveling, 17.77% to grooming, and 14.73% to playing (Alfred et al., 1998). Stanford (1991d) found that males tend to devote more time to resting than females, and females tend to spend more time eating than males. Gupta (1994) also studying this species at Sepahijala Wildlife Sanctuary found the group activity consisted of 32.6% feeding, 27.2% resting, 22.8% traveling, and 17.4% other activities. The group wakes up before dawn, not moving until after sunrise (Mukherjee, 1978). In the morning, sometimes individuals will bask in the morning sun, preferring to do this in higher branches will little or no foliage (Choudhury, 1990). Individuals will orient their backs and/or sides towards the sun, sometimes changing sides while sunbasking (Choudhury, 1990). The timing and direction of group movements are initiated by females of the group (Stanford, 1991a, d). Males tend to lag behind the group and are slow to stop eating (Stanford, 1991d). When moving, the group moves from tree to tree as a compact unit in the upper level of the canopy, jumping between small gaps and descending to the ground to negotiate larger gaps (Mukherjee, 1978). Groups will spend more time moving in the summer due to the lengthened hours of light (Islam and Husain, 1982). Vocalizations are rare when moving, limited to the nouk vocalization (Mukherjee, 1978). Feeding bouts are interspersed with periods of resting and short naps (Mukherjee, 1978). Feeding occurs mostly in the early morning and late afternoon (Mukherjee, 1978; Islam and Husain, 1982). Groups will find sleeping trees at dusk when dim light is still visible, sleeping one individual per sleeping tree (Choudhury, 1990). Juveniles and infants sleep with their mothers (Choudhury, 1990). Sleeping sites are in the top canopy levels, 20-30 meters above ground, on trees with little or no foliage, like Salmalia malabarica and Cassiasp. (Choudhury, 1990). Sleeping trees will differ from night to night (Choudhury, 1990). Islam and Husain (1982) found that group activity as a whole is highly synchronous.
The jackal, Canis aureus, is a potential predator of the capped langur (Stanford, 1989). Adult males will emit alarm bark upon sighting a jackal (Stanford, 1991a). Humans, Homo sapiens, will hunt capped langurs for food (Choudhury, 1990, 1989).
The capped langur moves through the forest quadrupedally (Fleagle, 1988). Moving between trees is done sometimes by leaping from one limb to another (Green, 1981). When leaping, propulsion is provided by the hindlimbs and the forelimbs first come into contact with the substrate when landing (Green, 1981). For the capped langur leaps have an average horizontal distance ranging from 2-4 meters, with leaps of up to 10 meters possible (Green, 1981). Most bouts of travel occur in the first half of the morning and in the latter half of the afternoon (Islam and Husain, 1982).
The social structure of the capped langur is mostly unimale, but multimale-multifemale groups are known to occur (Stanford, 1991a, 1987, 1988; Mukherjee, 1978; Green, 1981; Mukherjee et al., 1995). The basic group of this species is composed of one adult male, two to five adult females plus immatures (Stanford, 1991a). All-male groups and solitaries are found in this species (Stanford, 1991a, 1988; Green, 1981; Choudhury, 1988). Mukherjee (1978) studying the capped langur in Assam found in a group with two adult males, there would be threats and chases between the adult males. Both males and females will leave their natal group, and males will travel solitarily for a while until they find a group of their own. Females will allow other females of the group to carry and care for their infants (alloparental care) (Stanford, 1991c). Stanford (1991c) found that allomothers are usually parous adult females, and alloparenting allows lactating females to increase their feeding time.
Stanford (1991a) found that group home ranges will overlap, with an average of 84% overlap in groups found in Madhupur National Park. Alfred et al. (1998), studying capped langurs in Sepahijala Wildlife Sanctuary, also found that the home ranges of groups overlapped. Encounters between unimale group males tend to be higher in winter and during the rainy season and lower during spring and autumn (Stanford, 1991a). Males tend to exhibit aggressive displays against unimale group males that are unfamiliar (Stanford, 1991a, 1990). These displays consist of running through the crown of a tree in a circular path coupled with breaking branches and alarm vocalizations (Stanford, 1991a). The offending male will either not respond or respond causally or respond with aggression and reciprocate the display, sometimes chasing the other group's male (Stanford, 1991a). When an adult male of a unimale group encounters a group that they are familiar with, they will exhibit the vigilance-sit posture (Stanford, 1991a; Green, 1981). Stanford (1991a) found that when any animals would approach a unimale group, the group male would position himself between the intruder and the rest of the group adopting the penile display. Adult male in a unimale group will respond more aggressively towards solitary males or males from an all-male group than to adult males from other unimale groups (Stanford, 1991a). The males are more aggressive because solitary and males part of an all-male group will attempt to capture adult females to create groups of their own (Stanford, 1991a, 1990). Group males will also act aggressively to their females if they believe that the females are trying to go with another adult male (Stanford, 1991a). If a female would move towards a unfamiliar male, then the group male will rush over to the female and bite the back or the nape area of the female or chase the female (Stanford, 1991a). Group males will sometimes herd females together when a familiar or unfamiliar group approaches, like that found in the hamadryas baboon, Papio hamadryas (Stanford, 1991a; Kummer, 1968). So aggression towards other groups is not because of territoriality, but to protect group females and maintain the integrity of the group (Stanford, 1991a, 1990; Islam and Husain, 1982).
At Sepahijala Wildlife Sanctuary, the capped langur is sympatric with Phayre's langur, Trachypithecus phayrei, and golden langurs, Trachypithecus geei (Gupta, 1998). Gupta (1998) found that this species shared 35 food plant species with Phayre's langur and 26 food plant species with golden langurs. In the Sylhet and part of the Karerhat Range of Chittagong, Bangladesh, this species is sympatric with Phayre's langur (Khan and Ahsan, 1986). At Madhupur National Park, the capped langur is sympatric with the rhesus macaque, Macaca mulatta, and the slow loris, Nycticebus coucang (Stanford, 1988). At Rajkandi Reserve Forest this species is sympatric with Phayre's langur, rhesus macaques, pig-tailed macaques, Macaca nemestrina, and Hoolock gibbons, Hylobates hoolock (Stanford, 1988).
Play in the capped langur mostly occurs between juveniles and infants (Alfred et al., 1998). Alfred et al. (1998) found that at Sepahijala Wildlife Sanctuary, 4.05-14.37% of the time was devoted to play. Social play in this species consists of chasing, grappling, and grabbing and pulling the hair on top of the head (Green, 1981). Stanford (1991d) found that social play tends to disappear during the months of November to February. Infants will sometimes fall during social play, but that only appears to be dangerous because jackals can easily prey on infants when they are on the ground (Stanford, 1991d).
growl: This is a low intensity call that has a duration of 1-1.5 seconds (Green, 1981). This call is emitted by adult males when feeding (Green, 1981).
nouk: This call is emitted by adult group members when the group is moving through the trees (Mukherjee, 1978). This call may serve to coordinate group movements in the thick foliage (Mukherjee, 1978).
chortle: This call is similar to the growl and has a duration of 1-2.5 seconds (Green, 1981). This is given by adult males during encounters with other adult males (Green, 1981). This call may be the "agitation grunt" as described by Stanford (1991d), where this call is also given by adult females and has a sound like "uh-uh-uh-uh-uh."
alarm bark: This vocalization is given when an adult male sights a jackal, sees another one-male group, a solitary male or an all-male group (Stanford, 1989, 1991d; Green, 1981). This call is emitted by both adult males and females (Green, 1981). This call consists of 1-3 notes that are sharp and loud with an open mouth where the canines are showing (Green, 1981). The duration of this call is 0.3 seconds (Green, 1981). Stanford (1991d) describes this call as consisting of two notes that sound like an aspirated "ah-AH", having a moderately nasal tone.
distress call: This call is high-pitched and sounds like "eeeeh" (Stanford, 1991d). This call is emitted by adult females and juveniles when they are distressed as during a food squabble (Stanford, 1991d). After such an event of agonistic physical contact, reconciliation behavior is sometimes seen to occur proceeding this call (Stanford, 1991d).
ehh: This call is a low intensity call of 1 note (Green, 1981). This call was found to be emitted by subadult males and juveniles during play (Green, 1981).
whistle-trill: This call is emitted by infants when they are carried by their mothers and during independent explorations (Green, 1981). The mouth is open during this call, and it is a high frequency call, almost sounding like a screech (Green, 1981).
infant scream: This is heard when an infant is left alone (Choudhury, 1990).
penile display: This display is performed by the adult male of the group. The male to sit with his legs open and his penis erect. This serves to warn other males that an adult male is in the group.
face threat: This is when an individual shows an open-mouth face with the teeth exposed to another individual (Stanford, 1991d).
run display: This is when an adult male will run and leap throughout the tree crown, in a circular motion around the tree crown, while breaking foliage (Stanford, 1991d). Alarm bark is sometimes given during this display (Stanford, 1991d).
display stance: This is when an adult male will stand facing the group, with the hindquarters rigid and the tail looped over the back (Stanford, 1991d). This display is seen after or during encounters with extra group or other males (Stanford, 1991d).
invite groom: This is when one individual will present a part of the body to another for a long period of time with the desire to receive grooming (Stanford, 1991d).
hand threat: This is when one individual will lunge at another and slaps or grabs with one or both hands (Stanford, 1991d).
bite: This is when one individual will bite another with the desire to injure the other individual (Stanford, 1991d).
social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals. Females will groom males, but males will not reciprocate (Islam and Husain, 1982). Juveniles will groom males when at rest, but males will not reciprocate (Islam and Husain, 1982). Females will groom their infants, juveniles, and other females (Islam and Husain, 1982). Grooming is done with one or both hands, and mothers will sometimes hold their infants under on foot while grooming with two hands (Stanford, 1991d).
embrace: This is when two individuals will sit facing each other and wrap their arms around each other (Stanford, 1991d). For brief moments, sometimes, they will maintain face-to-face contact (Stanford, 1991d).
The capped langur gives birth to a single offspring about every two years (Stanford, 1991d). The birth for this species is from April to May at the start of the monsoon season (Stanford, 1987).
Stanford (1991d) found that copulations did not occur during the rainy season, the mating season is from October-April. Before copulation, females will sometimes present to males (Islam and Husain, 1982). The female will turn the head and look back at the male repeatedly (Stanford, 1991d). Females will sometimes head-shake when presenting to a male (Stanford, 1991d). As the male approaches, the female will wave the left arm towards the male (Stanford, 1991d). The male mounts the female from behind with the feet staying on the substrate (Stanford, 1991d). Copulation may also begin with the male following the female (Stanford, 1991d). The female may present to the male after this behavior begins (Stanford, 1991d). The male will mount and copulate once, then the female departs with the male following (Stanford, 1991d). Mounts of the capped langur can be either single or multi mounts before ejaculation (Stanford, 1991d). During multi-mounts, the male will watch the actions of the female partner between mounts (Stanford, 1991d).
head-shaking: This is where the female shakes her head back and forth before she presents to the male.
presenting: This behavior is performed by the female to elicit a copulation from the male; this pattern tells the male that she is ready for copulation (Estes, 1991). Head-shaking: precedes this display.
Infants spend most of their time during the first two months of life either with their mother or with an allomother (Stanford, 1991d). The one year old infant will still return to the mother during the daytime rest period and in the evening and will still be nursed by the mother (Stanford, 1991d). Infant capped langurs will start foraging with the rest of the group at around the age of 10-11 months (Stanford, 1991d).
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