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.
Communication Channels: visual ; acoustic
Perception Channels: tactile ; chemical
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.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: endangered
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.
Phayre’s leaf monkeys are hunted for food by local tribes of humans. They are also poached for their gall stones, which are used for medicinal purposes.
Positive Impacts: food ; source of medicine or drug
As consumers of fruits, Phayre's leaf monkies, Trachypithecus phayrei, may play a role in seed dispersal. The considerable consumption of foliage by this species may also influence plant composition in local ecosystems.
Ecosystem Impact: disperses seeds
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.
Plant Foods: leaves; flowers
Primary Diet: herbivore (Folivore )
Phayre's leaf monkeys, Trachypithecus phayrei, range from Eastern India to Southern China, including portions of Thailand and Vietnam.
Biogeographic Regions: oriental (Native )
Phayre’s leaf monkeys, Trachypithecus phayrei, are found in a variety of habitats due to human disturbance within its range. They often reside in mixed evergreen/deciduous primary and secondary forests. In thick evergreen forests, Phayre’s leaf monkeys can be found 15 to 50 m above the ground. In areas lacking these primary and secondary forests,this species depend on bamboo and small shrubs. Phayre's leaf monkeys may also be found along stream banks containing thick bamboo forests.
Habitat Regions: tropical
Terrestrial Biomes: rainforest
Little information is known regarding the lifespan of the Phayre’s leaf monkeys. Other species within the family Cercopithecidae have life spans of 20 to 30 years in the wild.
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.
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.
Average mass: male 7.4 kg; female 6.2 kg.
Range length: 1.07 to 1.3 m.
Sexual Dimorphism: sexes alike; female larger
Other Physical Features: endothermic ; bilateral symmetry
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 T. phayrei.
Known Predators:
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.
Mating System: polygynous
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.
Breeding season: Phayre's leaf monkeys breed intermittently throughout the year.
Average number of offspring: 1.
Average gestation period: 205.3 days.
Range weaning age: 12 (high) months.
Average time to independence: 1 years.
Range age at sexual or reproductive maturity (male): 3 to 4 years.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
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.
Parental Investment: male parental care ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents
Phayre's leaf monkey (Trachypithecus phayrei), also known as Phayre's langur, is a species of lutung native to South Asia and Southeast Asia, namely India, Bangladesh, and Myanmar. Populations from further east are now thought to belong to other species. It is listed as Endangered on the IUCN Red List and is threatened by hunting and loss of habitat.[1] The species epithet commemorates Arthur Purves Phayre.
The scientific name Presbytis phayrei was used by Edward Blyth in 1847 for two young individuals captured alive in the Arakan Mountains in Myanmar.[3] Phayre's langur is one of the most widespread members of the genus, but its actual distribution and intraspecific taxonomy remain controversial. Previously, three subspecies were recognized, namely T. p. crepusculus, T. p. phayrei and T. p. shanicus.[2]
Three separate species T. phayrei, T. melamera (formerly T. p. shanicus), and T. popa sp. nov. have been proposed based on mitochondrial genomes. Currently, the name Phayre’s leaf monkey refers to T. phayrei, residing in forests of East Bengal, Northeast India and western Myanmar, specifically, areas to the west of the Chindwin and Irrawaddy Rivers.[4]
Phayre’s langur is characterized by white coloration around the ventral, mouth, and eye area. The broad ring-shaped patches around the eyes resemble spectacles, contributing to the local name of “Chasma bandor” in Bengali, or spectacled monkey. The white fur is especially contrasting with the overall deep bluish-brown fur all over its body with darker shades at the head, below the elbows, and at the end of the tail.[5] There is a presence of a sagittal crest on the heads of both adult males and females, giving it a triangular shape. The infants have a straw-colored natal coat, making it easily distinguishable in a group.[6] The average head-body length ranges from 530–580 mm (21–23 in) in males and 495–580 mm (19.5–22.8 in) in females. The tail is usually longer than its body, with an average of 700 mm (28 in) for males and 750 mm (30 in), for females. In comparison to T. melamera and T. popa, it has a shorter tail length.[4] The average mass of Phayre’s langur is observed to be around 7.9 kg (17 lb) for males and 6.9 kg (15 lb) for females.[7]
In field studies males and females are differentiated through the shape of the patches around the eyes. Female have cone-shaped white patches bending in towards the nose while males have a rounder shape. This shape difference causes a slightly wider gap in males than in females.[8]
Like most Old World monkeys, it has the dental formula of 2.1.2.32.1.2.3[9] Distinctive to other colobines Phayre’s langur show craniodental adaptations such as medially positioned rows of teeth and stronger masseter pterygoid muscles for seed-eating.[10]
Pharye’s langur is found in tropical, deciduous, and evergreen forests of North-East India, Eastern Bangladesh, and Western Myanmar. It can also be seen residing in secondary forests such as bamboo clusters and rubber plantations. Tree species with large canopies like Artocarpus chama, Artocarpus lacucha, Ficus racemosa, Trophis aspera, Mangifera indica, and Grewia nervosa, in Bangladesh, are used for resting in their shade.[11] In India, the most common roosting trees range from heights of 6–15 m (20–49 ft) and have an extensive canopy, e.g., Ficus hispida and Triadica sebifera in Mizoram.[7] Currently, a total of 1200 individual langurs have been recorded in India and 376 individuals in Bangladesh,[1] 288 of which resided in the northeastern forests of Bangladesh.[12]
The Phayre’s langur usually forms multi-male and multi-female with a presence of a dominant male alpha in the group. All-male groups, one-male groups, and one-female groups have also been observed though, less common. A high level of territoriality is seen within the species and between groups.[7][13] The groups tend to maintain occupancy in their home range, showing philopatry.[7] Foraging is done by maintaining groups throughout different ranges. While foraging, groups tend to avoid ranging areas of neighboring groups suggesting the formation of borders between them, agonistic interactions are observed in places of overlapping borders.[7][14]
Female dispersal is also observed between the groups, females that leave the group tend to obtain alpha rank in the new group. Linear dominance is seen in females, where rank has a linear relationship with age.[15][16] Males on reaching maturation show some dispersal, they either form new multi-male groups or return to their natal group. For males, age and rank dominance also show a linear relationship though, the ranks can change depending on the resource-holding potential, which is shown to decrease in aging monkeys.[13]
Female Phayre’s langurs are pregnant by an average age of 5.3 years with an average gestation period of 205 days.[17] The females show promiscuous behavior, studies do show a preference for more experienced males, usually of higher dominance. Polygynous relationships are common, where males offer protection to copulated females.[13]
Females usually nurse their infants on average 22 months with weaning at around 19–21 months. The natal coat starts to become darker 26 weeks after birth.[18]
Vocalization is observed in both males and females. Based on observations in the wild, a loud “kah-kah-kah” is used to sound alarm in the troop, while in the presence of a predator a softer “whoo” call is used.[15] The dominant male alpha uses the “cheng-kong” sound to assemble the group. Additionally, vocalization essential is for maintaining contact with troop members while foraging. In agonistic interactions, barking sounds such as “ngre-go, ngre-go” are used to maintain their group's territory.[5][7]
The Phayre’s Leaf Monkey is diurnal and arboreal. The average life span of it being 20–30 years, in the wild, and an average of 28.3 in captivity.[7] A study conducted in the Satchari National Park, Bangladesh, found on average the Phayre’s leaf Monkey spends, most of its time foraging and feeding (40.7%), the rest is spent traveling (31.8%), resting (18.3%), grooming (7.8%) and playing (1.4%).[11] It is seen that males and juveniles tend to spend more time moving than adult females, who also have the highest percentage of resting among them. It is noticed that the activity patterns have variations based on habitats, seasons, and food availability, for example, food shortages lead to increased travel time. The variation in caloric content of different foods have shown to affect the energy budgets, i.e., poor quality food leads to higher feeding distribution to maintain the caloric requirements.[7][11]
The Phayre’s leaf monkey is a folivore. It feeds on leaves, shoots, seeds, flowers, gum, and fleshy parts of fruits. The diet varies between seasons and different regions, showing adaptation to the local flora.
In Dampa Tiger Reserve, the Phayre’s langurs feeds on Citrus grandis, Gmelina arborea, Ficus maclellendii, Buetneria pilosa, with a preference towards bamboos such as Musa ornata, Melocanna baccifera and Dendrocalamus longispathus during summer.[19] Plant parts with less fiber and high proteins and sugars such as young leaves are usually preferred while foraging.[7] In Satchari National Park in Bangladesh, they feed primarily on Ficus hispida, Albizia chinensis, and Vachellia nilotica.[11]
The high bamboo consumption in their diets is attributed to the abundance of this plant in North-East India because of its invasive nature.[20] Phayre’s langurs living in local rubber plantations in Mizoram majorly consume leaves of Hevea brasiliensis showing that diet is affected by the plant diversity in its home range.[7]
In Tripura, India, it mainly feeds on leaves of Albizia procera, Albizzia lebbek and A. stipulata, Melocanna bambusoides, Macaranga denticulata, Callicarpa arborea, Dillenia pentagyna, Litsea sp., Mikania scandens, Gmelina arborea, Artocarpus chaplasha, Syzygium fruticosum, Ficus racemosa, Ficus hispida, Ficus indica and F. fistulosa.[21]
The IUCN Red List has deemed the population of Phayre’s langur to be decreasing. The recent reclassification of Phayre’s langur has led to the underestimation of the status of the decline in the specie’s population. It is also listed in the CITES Appendix II, to protect its illegal poaching and trading locally. The major threats to Phayre’s langur are habitat destruction, fragmentation, logging, roadkill, ecotourism, electrocution and hunting.[11][22]
In India, organizations like the Wildlife Trust of India have employed wildlife staff trained in anti-poaching tactics to work in forests, and locals have also been involved.[15] In both India and Bangladesh, Pharye’s langur is protected through national and local legislation and through implementation of international conservation laws and policies, i.e., the Wild Life (Protection) Act, 1972, in India and Wildlife (Conservation and Security) Act, 2012, in Bangladesh .
The ‘jhooming‘, a form of shifting cultivation practiced by tribes in India, led to concerns over reducing forestland for the Phayre’s langur population, but a study showed that they adapted to the local practice. The regenerating secondary forests through ‘jhooming‘ provide a habitat for the langurs when primary forests are unsuitable to stay in due to anthropogenic factors.[23]
Phayre's leaf monkey (Trachypithecus phayrei), also known as Phayre's langur, is a species of lutung native to South Asia and Southeast Asia, namely India, Bangladesh, and Myanmar. Populations from further east are now thought to belong to other species. It is listed as Endangered on the IUCN Red List and is threatened by hunting and loss of habitat. The species epithet commemorates Arthur Purves Phayre.
