The three subspecies of Phayre's leaf monkeys, T. p. phayrei, T. p. crepusculus and T. p. shanicus are slightly different in coloration. In genral, Phayre’s leaf monkeys are dark grey-blue in color with some brown on the dorsal side and have mostly brownish-white pelage on the ventral side. The upper arms, legs, and tail are silvery-grey in color, and, in general, the head and tail are darker than the rest of the torso. The area around the lips and eyes are white. Young Phayre’s leaf monkeys exhibit yellowish colored fur until about 3 months of age when the pelage begins to change. Adult Phayre's leaf monkeys also have slightly longer hair on the top of their head. ("Phayre's Leaf-monkey", 2011)
Female Phayre's leaf monkeys are slightly larger than males. Whereas males range from 1.07 to 1.1 m in length, females range from 1.15 to 1.3 m. The tail of Phayre's leaf monkeys constitutes 68 % of the overall length, ranging from 65 to 86 cm. Males weigh an average of 7.4 kg and females an average of 6.2 kg. Male Phayre's leaf monkeys can be distinguished from females in the field is by observing differences between ocular markings. In males, the white ocular rings around the eyes are parallel to the side of the nose, resulting in a black strip uniform in width. In females, the white ocular rings around the eyes bend inwards toward the nose causing more of black triangular shape. (Bhattacharya and Chakraborty, 1990)
The mating system of Phayre’s leaf monkeys is similar to that of spectacled langurs Trachypithecus obscurus. Troops of Phayre’s leaf monkeys have one dominant male that breeds with multiple females. Because adolescent males leave the troop before reaching sexual maturity, males do not challenge the dominant male of or mate with females within their natal group. Outcast males may join other solitary males, becoming nomadic in search of breeding females or the opportunity to challenge a dominant male in order to establish his own troop. Dominant males protect their territory from troopless males. If an intruding male wins an encounter, the dominant male is then outcast, and the newcomer gains breeding rights. The new dominant male may kill young from the previous male, effectively permitting earlier copulation with females. ("Langurs and Leaf Monkeys", 2009; Yeager and Kirkpatrick, 1998)
Breeding of Phayre's leaf monkeys can be intermittent, and births generally occur in March and April. The gestation period from conception to birth is approximately 205 days. Females give birth to one offspring at a time, which nurse for almost a year. Males reach sexual maturity at 3 to 4 years of age. ("Phayre's Leaf-monkey", 2011; Larney, et al., 2007)
Phayre's leaf monkeys invest considerable energy in raising their young. Newborns nurse for almost a year, which greatly increases chance of survival. Mothers are the main caregivers as they feed, protect and groom newborns. It is not uncommon for older female siblings of a newborn to provide minimal care in the absence of the mother. Adolescent Phayre's leaf monkeys tend to keep some contact with their mothers, even after she gives birth to additional offspring. When young Phayre's leaf monkeys fall to the ground, they call out in distress to their mother. In most instances, the mother or an older sibling descend to retrieve it. In the case that an infant is lost from the troop the mother will give a "lost call" in hopes of locating the lost newborn. ("Langurs and Leaf Monkeys", 2009; Larney, et al., 2007)
Phayre's leaf monkeys are very shy and typically flee when threatened. They spend over 75% of their time feeding within tree tops. This speices rarely leaves the safety of the trees, leaving only if their requirements are not met or to negotiate gaps in the canopy. Phayre's leaf monkeys are strongly territorial against other groups of the same species, although sympatric groups of other species may share the same territory. ("Langurs and Leaf Monkeys", 2009; "Phayre's Leaf-monkey", 2011)
Group of Phayre's leaf monkeys vary in size from 8 to 22 members. One dominant male rules the group, composed of 3 to 6 adult females, and a mixture of sub-adults, juveniles, and infants. Females tend to be closely related to each other and rarely leave the troop. Their roles and level of dominance amongst females are not clearly defined. Adolescent males leave the troop at about 3 years of age before they reach sexual maturity, preventing males from challenging the dominant male of or mating with females e within their natal group. Outcast males may join other solitary males, becoming nomadic in search of breeding females or the opportunity to challenge a dominant male in order to establish his own troop. Dominant males protect their territory from troopless males. If an intruding male wins an encounter, the dominant male is then outcast, and the newcomer gains breeding rights. ("Langurs and Leaf Monkeys", 2009; "Phayre's Leaf-monkey", 2011; Yeager and Kirkpatrick, 1998)
Phayre's leaf monkeys have home ranges from 10 to 100 ha, with very little overlap among groups. The size of the range depends heavily on the distribution and abundance of food. If food resources are limited, larger groups will increase the size of their home range in search of food. Although range is mainly determined by group size, group size is heavily limited by social stress. Stress limits population size and thus home range in three ways: stress reduces a female’s ability to conceive and carry an infant to term; stress can lead to immunosuppression making individuals more susceptible to disease and therefore death; and stressed Phayre’s leaf monkeys may disperse, leaving their group, which puts them at a greater risk of death. ("Langurs and Leaf Monkeys", 2009; Yeager and Kirkpatrick, 1998)
Both male and female Phayre's leaf monkeys use vocal calls for a variety of reasons. Adult males use a loud "kah kah kah" call when alarmed. A softer "whoo" call is used when adult males detect a predator within the area. The "cheng-kong" call is emitted by the dominant male to bring the group together. When a dominant male must defend its territory, a "loud call" is used, which is a high pitched roar against intruders. Young Phayre's leaf monkeys will emit a distress call when they fall from the treetops. Femals also use a “lost call” in an attempt to locate lost newborns. This call has also been heard from Phayre's leaf monkeys in the presence of deceased newborns. ("Phayre's Leaf-monkey", 2011)
Phayre’s leaf monkeys are folivores, eating primarily leaves. They have been know to eat leaves from approximately 80 different species of plants. Due to the considerable about of leaves in their diet, Phayre's leaf monkeys have highly adapted stomachs, necessary to digest cellulose and denature the toxins found in leafy materials. Phayre's leaf monkeys also eat bamboo shoots when tree foliage is not as abundant. ("Langurs and Leaf Monkeys", 2009; "Phayre's Leaf-monkey", 2011)
The main predators of Phayre’s leaf monkeys are humans. Native tribes within their ranges, hunt this species for meat. Because the gall stones of Phayre’s leaf monkeys are used for medicinal reasons, poaching by humans is also a threat, particularly around salt springs. Newborns may also be vulnerable to large tree snakes and raptors which are a threat to similar species, though no data on actual predation rates are readily available for . ("Langurs and Leaf Monkeys", 2009; "Phayre's Leaf-monkey", 2011)
Conservation efforts have limited slash and burn cultivation and have led to increased protected land, which some would consider as adverse effects toward humans. Local bush hunting is also decreasing as conservation efforts increase. ("Langurs and Leaf Monkeys", 2009; Bose, 2003)
Habitat loss and fragmentation are the biggest threats to the continued survival for Phayre’s leaf monkeys. With isolated populations scattered throughout their range, the viability of these populations is currently unknown. It is estimated that 1,300 individuals currently exist in the wild. (Bose, 2003; Larney, et al., 2007)
wayne cantwell (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Gail McCormick (editor), Animal Diversity Web Staff.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
An animal that eats mainly plants or parts of plants.
parental care is carried out by males
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
having more than one female as a mate at one time
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
2009. "Langurs and Leaf Monkeys" (On-line). JRank Science Encyclopedia. Accessed March 12, 2009 at http://science.jrank.org/pages/3821/Langurs-Leaf-Monkeys.html.
2011. "Phayre's Leaf-monkey" (On-line). The Primata. Accessed January 25, 2011 at http://www.theprimata.com/trachypithecus_phayrei.html.
Bhattacharya, T., D. Chakraborty. 1990. Sex Identification of the Phayre's Leaf Monkey, with the Help of Facial Marks. Primates, 31(4): 617-620.
Bose, J. 2003. Conservation Survey of Phayre's leaf Monkey. Wildlife Trust of India, 1: 1-36.
Johnson, D. 2008. "The Lifespans of Nonhuman Primates" (On-line). Primate Info Net. Accessed March 13, 2009 at http://pin.primate.wisc.edu/aboutp/phys/lifespan.html.
Larney, E., A. Yamee, L. Gibson, D. Pesek, T. Whitty, B. Whitman, A. Bprasapmu, W. Nueorngshiyos. 2007. Return of Wild Phayre's leaf Monkey Infants to their Social Group in Phu Khieo Wildlife Sanctuary, Thailand. Natural History Bullitin Siam Society, 55(1): 193-196.
Snaith, T., C. Chapman. 2007. Primate Group size and Interpreting Socioecological Models: Do Folivores Really play by Different Rules?. Evolutionary Anthropology, 16: 94-106.
Yeager, C., C. Kirkpatrick. 1998. Asian Colobine Social Structure: Ecological and Evolutionary Constraints.. Primates, 39(2): 147-155.