Phayre's Leaf-monkey (Trachypithecus phayrei)

This species has a sacculated stomach to assist in the breakdown of cellulose. Phayre's leaf-monkey has enlarged salivary glands to assist it in breaking down food. The dental formula of Phayre's leaf-monkey is 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). Males have larger canines than females (Pan et al., 1993). The length of the head and body range from 44-61 centimeters and tail length for this species ranges from 65-86 centimeters (Choudhury, 1987). The average body mass of an adult male Phayre's leaf-monkey is around 7.3 kilograms, and for the female it is around 6.2 kilograms (Fleagle, 1988). The pelage color for Phayre's leaf-monkey is dark ashy-bluish brown on the dorsal side and whitish on the ventral side (Choudhury, 1987). The head and tail ends of this species are darker than the rest of the body (Choudhury, 1987). Srivastava (1999) describes the upper arms, legs, and tail as being silvery gray in coloration. The lips and the area around each of the eyes are whitish (Choudhury, 1987). Infants are straw colored (Roonwal and Mohnot, 1977). Srivastava (1999) describes the infants as being orange in color that begins to change after 3 months of age. This species has an extended cap of hair on the head that occurs in all individual except newborn infants (Srivastava, 1999).

This species has three subspecies each having differing pelage colorations:

Phayre's leaf-monkey is found in the countries of Bangladesh, Burma, China, India, Thailand, and Vietnam (Srivastava, 1999; Roonwal and Mohnot, 1977; Gupta and Kumar, 1994; Stanford, 1988; Ruggeri and Timmins, 1995/1996). In India, this species is found in Tripura, Mizoram, and Assam (Choudhury, 1987, 1994; Mukherjee, 1982; Srivastava, 1999). In Assam, Phayre's leaf-monkey is found in the districts of Cachar, Hailakandi, and Karimganj (Choudhury, 1996). This species is found in Huai Kha Khaeng Reserve, Thailand and in Pidaung and Pegu Yoma Reserves in Burma (MacKinnon and MacKinnon, 1987). This species lives in primary and secondary forests, and also on tea estates where bamboo thickets are found (Wolfheim, 1983; cited in Nisbett and Ciochon, 1993). In Assam Phayre's leaf-monkey was found to live in depleted evergreen forests containing bamboo, favoring habitats dominated by the shrub Macaranga denticulata and the herb Alpinia allughas (Choudhury, 1987, 1994, 1996). In Mizoram this species was found in secondary forests and a dense bamboo forest with a few scattered trees (Raman et al., 1995). In Bangladesh this species lives in semi- evergreen forests and semi-deciduous/evergreen forests (Feeroz et al., 1995; Gittins and Akonda, 1982). In Vietnam, this species is found in the localities of: Phu Quy, Muong Cha, Phu Yen, Lang Chanh, Quan Hoa, Nghia Dung, and Quy Chau (Nisbett and Ciochon, 1993; Wolfheim, 1983). Ratajszczak (1988) reports that this species is found in Cuc Phuong National Park in Vietnam. In Burma, this species lives in dense high forests and in bamboo forests along hillsides and along the banks of streams (Roonwal and Mohnot, 1977). In Thailand, Phayre's leaf-monkey lives in evergreen forests, 15-50 meters above the ground (Roonwal and Mohnot, 1977). Phayre's leaf- monkey is found in higher densities in mixed-species plantations than in monoculture plantations (Gupta, 1997).

This species has three subspecies each having a differing range:

Phayre's leaf-monkey is a folivorous species (Ahsan, 1994; Roonwal and Mohnot, 1977; Gupta and Kumar, 1994; Stanford, 1988; Choudhury, 1994; Gupta, 1996; Bose and Bhattacharjee, 2002). This species prefers to consume immature leaves to more mature ones (Bose and Bhattacharjee, 2002). In the Inner Line Reserve Forest of Assam, this species was found to mainly consume bamboo shoots (Srivastava, 1999). In southern Assam the three most preferred food items were Teinestachum dulloea, Dendrocalamus griffithii, and Mokania micrantha (Bose and Bhattacharjee, 2002). At Sipahijala, Tripura, young rubber shoots are an important part of the diet during the dry season (Srivastava, 1999). Gupta (1997) found that 38% of the total time feeding was spent on feeding on plantation species. An exotic plantation species, Akashmani (Acacia auriculiformis), accounted for 18.3% of the time feeding on plantation species (Gupta, 1997). There are two feeding peaks for this species, one in the early morning and one in the late afternoon (Srivastava, 1999). Phayre's leaf-monkey will sometimes break-up into subgroups when foraging (Srivastava, 1999; Choudhury, 1994). Groups will spread out far when foraging (Ahsan, 1994). More time is devoted to feeding during the winter months (36.9%) than in summer (33.6%) or the monsoon (31.1%) months (Gupta and Kumar, 1994).

Gupta and Kumar (1994) found that in Gumti Wildlife Sanctuary, Tripura, India, the diet consists of young and mature leaves, ripe and unripe fruits, seeds, petioles, flowers, and gums. Gupta and Kumar (1994) over an eight month study found that young leaves consisted of 48.5% of the diet, followed by the young pods and seeds of two leguminous species (Albizzia procera and Albizzia lebbek), unripe and partly ripe fruit of two Ficus species accounted for 5.2% of the diet, and the last 20.6% of the diet consisted of petioles, gums, and flowers. Young leaves were consumed most in June (81.7%) and least in March (22.0%) (Gupta and Kumar, 1994). Seeds were found to be more in the months of January, February, and March when eating young leaves was low (Gupta and Kumar, 1994). Feeding on mature leaves was low, only consisting of feeding on the leaves of the bamboo species Melocanna bambusoides (Gupta and Kumar, 1994). Gupta and Kumar (1994) found that the feeding on young leaves depended on their abundance and not their availability. The most important food sources at Gumti Wildlife Sanctuary were Albizzia procera, Melocanna bambusoides, Callicarpa arborea, and Albizzia stipulata, Albizzia lebbek (Gupta and Kumar, 1994). Albizzia procera was used the most with its young leaves, pods and seeds, and gum being utilized (Gupta and Kumar, 1994).

Group sizes range from 3 to 30 individuals. In Yunnan, China, group sizes for this species were found to range from 30-40 individuals (Zhen, 1991; cited in Pan et al., 1993). He and Yang (1982; cited in Pan et al., 1993) found that group sizes ranged from 4-8 individuals. In Bangladesh, the mean group size was found to be 11 individuals (Ahsan, 1994). In Rajkandi Reserve Forest, Bangladesh, group sizes were found to average 8.8 individuals (Stanford, 1988). This is an arboreal and a diurnal species, although it will move around the ground occasionally to move or to feed (Choudhury, 1994). Groups have a relatively small home range size due to a high percentage of folivory (Gupta, 2002). Daily activity consists of feeding (34.9%), resting (21.15), traveling (14.4%), and other (29.5%, playing, grooming, etc.) (Gupta and Kumar, 1994). More time is spent feeding and less time resting during the winter months (Gupta and Kumar, 1994). Gupta (1997) found that in another study (12 months), in Tripura, India, daily activity consisted of 41.7% feeding, 28.3% resting, 8.2% traveling, and 21.8% other activities (grooming, calling, playing, suckling, aunting, etc.). Bose and Bhattacharjee (2002) found that in southern Assam, group daily activity consisted of 39.4% feeding, 14.8% moving (traveling), 34.4% resting, 7.2% grooming, 1% playing, and 3.2% other activities. Groups will awake shortly before dawn, feed, then find a place to rest (Choudhury, 1994). In the late afternoon, groups will feed again (Choudhury, 1994). During the winter months, individuals will bask in the sun like capped langurs (Choudhury, 1994). Sleeping sites range in height from 8 to 29 meters (Gupta, 2002).

Phayre's leaf-monkey moves through the forest quadrupedally (Fleagle, 1988).

Phayre's leaf-monkey has either a unimale or a multimale-multifemale social system; in the multimale-multifemale usually there are two males (Gupta and Kumar, 1994; Choudhury, 1994). The number of females in a group will range from 3 to 6 (Gupta and Kumar, 1994). Solitary individuals have been reported for this species (Srivastava, 1999). This is a territorial species and will defend its territory against conspecific groups. When a group is alarmed, the females will grab their infants and run throughout the forest, leaping from tree to tree while a male stays behind to watch and bark at the intruder (Roonwal and Mohnot, 1977). Infants will be transferred between females (Srivastava, 1999). Gupta (2000) observed a group's reaction to a dead member of the group and found that they remained close to the body, touching and caressing it. Gupta (2000) also found that a neighboring group also came near the body, but there was no aggression between the groups, which is usually expected. Neighboring groups may be related and the second group may have protected the first group from predators because the dead body was on the ground and Phayre's leaf-monkey rarely descends to the ground (Gupta, 2000). Remaining close to the body may reduce the stress of the group members (Gupta, 2000).

In the West Bhanugach Reserve Forest of Sylhet, Bangladesh, Phayre's leaf-monkey is sympatric with the capped langur, Trachypithecus pileatus (Feeroz et al., 1995). This species is also sympatric with the capped langur in Rajkandi Reserve Forest where they will feed in the same or adjacent trees (Stanford, 1988).

Humans, Homo sapiens, predate upon Phayre's leaf-monkey (Roonwal and Mohnot, 1977). Leopards, Panthera pardus, is a potential predator of this species (Stanford, 1988).

loud call: This call is described as being a high pitched roar (Stanford, 1991).

whoo call: This is a soft warning call emitted by the adult male upon detection of a predator (Srivastava, 1999).

cheng-kong call: This is a two-phased honking call emitted by the adult male to bring the group together (Srivastava, 1999).



social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals.

Phayre's leaf-monkey gives birth to a single offspring. Females will experience 3.57 menstrual cycles to conception (Lu et al., 2010). Average gestation length for this species was found to be 205.3 days (Lu et al., 2010).

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Last Updated: January 11, 2011.
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