Trachypithecus poliocephalus (Trouessart, 1911)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 748-749

153.

Cat Ba Langur

Trachypithecus poliocephalus

French: Langur a téte dorée / German: Cat-Ba-Langur / Spanish: Langur de Cat Ba

Other common names: Golden-headed Langur

Taxonomy. Semnopithecus (Lophopithecus) poliocephalus Trouessart, 1911 ,

the type locality is supposed to be the village Cai Kien (21° 19° N, 107° 44’ E), or the Cai Kinh limestone massif 21° 45’ N, 107° 30’ E.

These type localities are outside the known distribution of 1. poliocephalus , and itis proposed to restrict it to Cat Ba Island, Vietnam. In the past, 1. poliocephalus was mostly classified as a subspecies of 1. francoisi or placed as the nominate taxon together with 7. leucocephalus . It is a member of the francoisi species group, also known as the karst or limestone langurs. Monotypic.

Distribution. Cat Ba I in Ha Long Bay, off N Vietnam.

Descriptive notes. Head-body 49-59 cm (males) and 49-55 cm (females), tail 82-92 cm (males) and 82-89 cm (females); weight 8.9-5 kg (males) and 6.7-8 kg (females). Pelage of adult male and female Cat Ba Langursis a dark chocolate-brown, not black. Head and neck, down to shoulders, is bright golden-brown to yellowish-white, with head and crest being the lightest colored parts. Hairs on head form a crown crest; central hairs of crest are often brown tipped. A 5cm-wide gray band runs from thighs to back, above root oftail. This band forms a V-shape, with the tip on lower back. Hairs of the band are dark brown,like the rest of back, but 5—10 mm of the tips are bright silver gray, giving the band a “frosted” appearance. Feet and hands have small yellow patches that are the same color as shoulders. Female Cat Ba Langurs have a skin patch in their pubic areas, with irregular pigmentation and pale white or yellowish hairs. They have very long hairs on their backs, with hair length up to 180 mm that form a back cape. All bare skin, including on face, ears, hands, and feet, is black. Cat Ba Langurs are born with a bright yellow-orange pelage. After c.6 months, back and tail grow darker, and there is an increase in the contrast between head and shoulders and the back. A shine of silver-gray hair indicates beginning of the band running from thighs to back. Coat grows darker, and after 1-5-2 years, individuals have adult coloration.

Habitat. Forests on limestone (karst) hills. Cat Ba Langurs belong to the so-called “limestone langurs.” Especially in winter, groups use caves and crevices as sleeping places. The region is characterized as a humid, subtropical monsoon area, with pronounced wet and dry seasons. The rainy season lasts from May to September, with the heaviest rainfall occurring in July-August. Dry and cold seasons last from November to March. Mean annual rainfall is ¢.1800 mm, and temperatures can drop to 0°C.

Food and Feeding. Cat Ba Langurs are mainly folivorous, with leaves making up the highest percentage of their diets, and the remainder composed of shoots,fruits, flowers, and bark. Their preferred habitat is bush and shrub plant communities. Ninetyeight plant species from 42 families have been recorded in their diet.

Breeding. Cat Ba Langurs are born throughout the year but with a peak in the beginning of the year. Females give birth to a single offspring.

Activity patterns. Cat Ba Langurs are diurnal, crepuscular, arboreal, and terrestrial. Sleeping places, mostly caves or crevices, are left before dawn. Peak feeding times are 07:00-09:00 h, 11:00-12:00 h, and 15:30-17:00 h. In the afternoon, groups move near cliffs with caves and remain in the vegetation. When they finally arrive at their sleeping cave, it is nearly dark (summer c.18:30 h and winter ¢.17:30 h). On average, 66% of the day is spent resting, 15% feeding, 11% traveling, and 8% engaging in social behavior (observations in April-May). Activity budgets of adults andjuveniles are similar, but infants spend 33% oftheir daily activities engaged in social behavior, including playing, and they spend less time in resting.

Movements, Home range and Social organization. Groups of Cat Ba Langurs move systematically, not randomly, through their home range. Like other langurs of the “limestone langur” group, quadrupedalism is the most frequent form of locomotion on both rocks and in trees. Following a rest period, a group generally moves to a new location. During rest periods, group members usually stay close together. Some individuals are in close contact, while others are separated by 10-20 m. At feeding times, distances between individuals increase up to ¢.100 m. The adult male in the group usually initiates movement. The male starts to move to a higher elevation and then sits down 100-300 m from other group members to observe the locality, sometimes for 15-30 minutes. If the group follows him, the male relocates to another observation point. They often use tops of cliffs to inspect the surrounding area, while the group below moves from one slope or valley to another. During walking, running, and leaping, Cat Ba Langurs display a concave downward arch of theirtails, as in the northern distributed species of the “limestone langurs,” Francois’s Langur (71. francoisi ), the White-headed Langur (7. leucocephalus ), and Delacour’s Langur (71. delacouri ). This tail posture differs from the southerly distributed species, the Hatinh Langur (7 hatinhensis ), the Laos Langur (7. laotum ), and the Black Langur (7. ebenus ). There is little information on home ranges of Cat Ba Langurs. Distances between observations of one group were only 1-2 km, and the home range was c.30 ha. Groups are composed of an adult male, several adult females, and their offspring. Surplus males live alone or join together in bachelor groups. In the past, group size in an undisturbed population was 8-10 individuals. In 2000, an average group size of 5-8 individuals was recorded on Cat Ba Island. In 1992, the population density was estimated at 0-003 ind/km?.

Status and Conservation. CITES Appendix II. Classified as Critically Endangered on The IUCN Red List. The Cat Ba Langur has been listed as one of the “World's 25 Most Endangered Primates ” since 2000. It is protected by Vietnamese law. The current total population is only 65-70 individuals. Despite widely intact habitat, the population is fragmented into 5-7 groups that have very limited or no contact. The historical density of Cat Ba Langurs on the island is unknown. According to older villagers and early scientific visitors, they occurred in high numbers in the past. It is assumed that the entire island of Cat Ba (c.140 km?) had previously been optimal habitat and could have supported at least 2400-2700 individuals. The population began to decrease in the 1960s, and this decrease was further accelerated by an increase in human settlements in subsequent decades. Between 1970 and 1986, ¢.500-800 Cat Ba Langurs were killed. Despite protection of most Cat Ba Langurs inside Cat Ba National Park, the population of 104-135 individuals in 2000 declined by roughly 50% by 2005. Poaching for meat and traditional medicine has been the most severe threat. A preferred hunting practice has been to catch Cat Ba Langurs, mostly the whole group,inside a sleeping cave. Habitat disturbance and fragmentation have resulted from the growing human population on Cat Ba Island, in part because of the country’s designation of the island as a new tourism center for northern Vietnam. Rampantfires started by honey collectors are also threats. Tourism in the inadequately managed Cat Ba National Park in the past has directly affected the natural history of Cat Ba Langurs by direct disturbance to the habitat. In 2000, a captive breeding program was established at the Endangered Primate Rescue Center, Cuc Phuong National Park, Vietnam.

Bibliography. Brandon-Jones (1995b), Duckworth & Walston (1998), Fooden (1996), Groves (2001), Le Xuan Canh & Campbell (1993/1994), Lowe (1947), Nadler (1996¢, 1999a, 1999b), Nadler & Ha Thang Long (2000), Nadler et al. (2003), Pham Nhat (2002), Ratajszczak (1988), Ratajszczak et al. (1990), Roos et al. (2007), Schneider et al. (2010), Schrudde, Levelink & Raffel (2010), Schrudde, Stenke et al. (2009), Stenke & Chu Xuan Canh (2004), Stenke et al. (2008), Stevens et al. (2008).

Figures

149. Tenasserim Langur (Trachypithecus barber), 150. Dusky Langur (Trachypithecus obscurus), 151. Phayre’s Langur (Trachypithecus phayrei), 152. Indochinese Gray Langur (Trachypithecus crepusculus), 153. Cat Ba Langur (Trachypithecus poliocephalus), 154. White-headed Langur (Trachypithecus leucocephalus), 155. Delacour’s Langur (Trachypithecus delacouri), 156. Francois’s Langur (Trachypithecus francoisi), 157. Black Langur (Trachypithecus ebenus), 158. Laos Langur (Trachypithecus laotum), 159. Hatunh Langur (Trachypithecus hatinhensis)

Distribution. Cat Ba I in Ha Long Bay, off N Vietnam.