Cat Ba Langur – Trachypithecus poliocephalus – (Pousargues, 1898)

Science name: Trachypithecus poliocephalus – (Pousargues, 1898)

Taxonomic:  Animalia>> Chordata>> Mammalia>> Primates >> Cercopithecidae >> poliocephalus

Species status: Endemic ; IUCN status: CR (Critically Endangered Species)

Description:

Physical Characteristics: Adult Trachypithecus poliocephalus individuals have thick, coarse fur. Their heads and shoulders are covered in yellowish-white fur, while their body and tail remain black. A crest of golden-yellow hair extends from their heads. The tail is long and thickly covered in black fur. Juveniles are born with light yellow fur, which changes as they mature.

Distribution and habitat:

Altitude: Trachypithecus poliocephalus inhabits elevations ranging from sea level to approximately 130 meters above sea level.

Range: This species is endemic to Cat Ba Island in Ha Long Bay, off the northeastern coast of Vietnam. Its area of occupancy is extremely small, covering less than 22 km², and it is restricted to Cat Ba National Park. The expansion of the park in 2006 included the monkey’s habitat, which provided greater protection for the species.

Habitat: Trachypithecus poliocephalus is primarily associated with limestone karst forests and is often found in caves, which offer shelter from predators and temperature extremes. It is both arboreal and terrestrial, diurnal, and mildly crepuscular. This species thrives in subtropical/tropical moist lowland forests, and their home range typically covers 30–50 hectares. Caves within their habitat are also used as sleeping sites.

Behaviour and ecology: 

Social Structure: The social composition of Trachypithecus poliocephalus includes unimale-multifemale groups. Despite the small population size, bachelor bands with several males have been observed. Group sizes range from solitary individuals to as many as 23 animals. Due to the disturbed nature of their habitat, there is no established baseline for what a natural group size should be.

Feeding Habits: This species is mainly folivorous, with 75-87% of their diet consisting of leaves. They also consume fruits, flowers, and stems. A study identified 98 plant species from 42 families that make up their diet.

Reproduction: Breeding occurs year-round, with a notable increase in births during the winter months, particularly from February to April. Gestation lasts about six months, and single offspring are typically born. The peak conception period is August, near the end of the rainy season.

Conservation and status: 

IUCN Red List Category and Criteria: Trachypithecus poliocephalus is listed as Critically Endangered under criteria D. The species faces severe population constraints, with fewer than 50 mature individuals remaining, all on Cat Ba Island. Although the population trend is increasing, the species remains at high risk due to its limited range and threats from human activities.

Population Trend: The population is increasing slowly, but the total number of mature individuals is estimated to be only 30-35.

Threats: Habitat destruction from tourism, fires, and development poses significant threats to the species. Additionally, hunting and human encroachment into their habitat have contributed to their decline. Their habitat, limestone karst forests, is highly susceptible to human impact, which further endangers their survival.

Conservation Actions: Trachypithecus poliocephalus is listed in Appendix II of CITES and is protected by Vietnamese law. Conservation efforts on Cat Ba Island, particularly within Cat Ba National Park, have contributed to the species’ slow population recovery. However, ongoing threats, particularly from habitat disturbance and poaching, continue to endanger this species.