Rhinopithecus avunculus, Dollman, 1912

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 : 727

125.

Tonkin Snub-nosed Monkey

Rhinopithecus avunculus

French: Rhinopitheque du Tonkin / German: Tonkin-Stumpfnase / Spanish: Rinopiteco de Tonkin

Taxonomy. Rhinopithecus avunculus Dollman, 1912 ,

Yen Bay, Songkoi River, Vietnam.

This species is monotypic.

Distribution. NW Vietnam, known only from small forest patches in Ha Giang, Tuyen Quang, Bac Kan, and Thai Nguyen provinces.

Descriptive notes. Head—body 55-65 cm (males) and 50-54 cm (females), tail 82— 92 cm (males) and 65-73 cm (females); weight 14 kg (males) and 8-5 kg (females). The Tonkin Snub-nosed Monkey is smaller, darker, and more slender in build than the other four species of Rhinopithecus . It has more elongated digits. Males and females have the same pelage coloration. Back and outsides of legs and arms are dark brown. Head, belly, and inner sides of limbs are creamy-white, this latter tone extending high up flanks, around face, and down limbs (leaving only a thin black stripe down outer sides to hands and feet); on elbows, in particular, the creamy-white color from insides of arms nearly encloses outsides of arms. Hands and feet are black. There is a small orange collar on the throat. Facial skin is bluish-white around eyes and nose, and lips are pink and enlarged. Adults have a notably upturned nose. Ears with creamy fur stand out at right angles from head. Tail is very long (nearly 170% of head—body length), with curly, intermixed black and strawcolored hairs along upper surface, a white underside, and a creamy-white tip with a thin tassel. Penis is black, and scrotum is white.

Habitat. Steep limestone karst hills with subtropical evergreen limestone forest and forest patches with bamboo at elevations of 200-1300 m.

Food and Feeding. The Tonkin Snub-nosed Monkeyis a selective feeder. When feeding, it dedicates c.40% of its time to young leaves, 18% to unripe fruits, 14% to flowers, 10% to young stems, and 6% each to buds, seeds, and mature leaves. It feeds on young leaves, unripe fruits, and seeds of as many as 52 plant species. In the most recentfield study, proportions of young leaves in diets varied from 11% in December—May up to 46% in September, while proportions offruit fell from 47-63% to 24%. In December— May, 26% of the diet in this study consisted of petioles, and the rest was flowers, mature leaves, seeds, and leaf buds.

Breeding. Little is known about breeding of the Tonkin Snub-nosed Monkey. Births occur most during the first half of the year. A single young is born, with a creamyyellowish fur. After 1-2 months, the colorstarts to darken and changes slowly to brown.

Activity patterns. Tonkin Snub-nosed Monkeys are diurnal, arboreal, and occasionally terrestrial. They spend ¢.33% of their day resting, 20% traveling, 30% watching and feeding, and the rest engaging in different social activities. Groups do not have fixed sleeping sites. They generally sleep close to the ground, on steep mountainsides, away from the wind, at ¢.5-10 m high in trees, sometimes in dense foliage. The Tonkin Snub-nosed Monkey travels on large tree branches by quadrupedal and occasionally bipedal walking and in the canopy, by leaping, jumping, and brachiating.

Movements, Home range and Social organization. Typical social unit of the Tonkin Snub-nosed Monkey is a unimale—multifemale group of 12-15 individuals, sometimes up to two dozen. The home range of one group was 380-560 ha. In the much depleted remaining population in Tat Ke and Khau Ca, the size of one-male groups was 7-13 individuals, with 2-6 adult females, 1-2 subadults, 1-3juveniles, and 1-4 infants. Home ranges of the groups overlap considerably. Groups often travel, forage, and rest together in large semi-cohesive bands. Males disperse from their natal groups to form all-male groups; all-male groups in remnant populations consist of 1-2 adult males and 2-3juvenile males. At times (it is not quite clear in what seasons or under what stimulus), these groups join to form large bands. In Khau Ca, a band of 78-81 individuals appeared to contain the entire population.

Status and Conservation. CITES Appendix I. Classified as Critically Endangered on The IUCN Red List. The Tonkin Snub-nosed Monkey is protected by law in Vietnam. It has been on the list of the “World’s 25 Most Endangered Primates ” since it wasfirst drawn up in 2000. Historically limited to areas east of the Red River,its distribution has been drastically reduced in recent decades because of massive deforestation and intensive hunting. It was thought to be extinct until its rediscovery near the town of Na Hang in 1989. Only a few degraded small populations exist. There are no exact numbers on the sizes of the subpopulations. An estimate is ¢.30 individuals for Na Hang Nature Reserve. A population of 70 individuals was estimated for Cham Chu Nature Reserve but recent surveys failed to produce evidence that Tonkin Snub-nosed Monkey still exist in the area. About 100 individuals live in the Tonkin Snub-nosed Monkey Conservation Area in Khau Ca, Ha Giang Province, and probably 50 in Quan Ba District, close to the Chinese border in the same province. The total population is believed to be less than 200 individuals. Despite their legal protection and the fact that they are one of the world’s rarest primates, Tonkin Snub-nosed Monkeys continue to be hunted mercilessly for use in Chinese medicine; they are rarely eaten because the flesh is considered foul tasting. Illegal logging takes place in the habitat of the Tonkin Snub-nosed Monkey. Shifting and settled cultivation, as well as other land development activities, also pose threats. In the past, intense and unsustainable legal and illegal logging and gold mining were the biggest threats. Recently, development of a hydroelectric power project along the Gam River in Na Hang has led to an increase in the human population and the demand for meat (despite the poor taste), and thus increased hunting pressure. The total population was estimated at ¢.250 in 2006, although this figure may now be higher due to possible occurrence in other areas. The Tonkin Snub-nosed Monkey occurs in four protected areas: Cham Chu Nature Reserve, Than Sa—Phuong Hong Nature Reserve, Tat Ke Sector of Na Hang Nature Reserve, and Khau Ca Habitat in Vietnam. It may also survive in Ba Be National Park, although the most recent search by Thanh Hai MaDong did not find any there; there may be a very small population in South Xuan Le Habitat.

Bibliography. Boonratana & Le Xuan Canh (1994, 1998a, 1998b), Covert et al. (2008), Dong Thanh Hai (2007, 2012), Dong Thanh Hai & Boonratana (2006), Dong Thanh Hai et al. (2006), Le Khac Quyet (2004b, 2008), Le Khac Quyet & Covert (2010), Le Khac Quyet & Simmons (2002), Le Khac Quyet, Dong Thanh Hai & Nadler (2009), Le Khac Quyet, Vu Ngoc Thanh & Luu Tuong Bach (2008), Le Xuan Canh & Boonratana (2006), Liedigk et al. (2012), Nadler & Streicher (2004), Nadler, Momberg et al. (2003), Nadler, Vu Ngoc Thanh & Streicher (2007), Nguyen Nga (2000), Pham Nhat (1992/1993, 2002), Wirth (1992).

Figures

122. Red-shanked Douc (Pygathrix nemaeus), 123. Gray-shanked Douc (Pygathrix cinerea), 124. Black-shanked Douc (Pygathrix nigripes), 125. Tonkin Snub-nosed Monkey (Rhinopithecus avunculus), 126. Yunnan Snub-nosed Monkey (Rhinopithecus bet), 127. Guizhou Snub-nosed Monkey (Rhinopithecus brelichi), 128. Golden Snub-nosed Monkey (Rhinopithecus roxellana), 129. Stryker’s Snub-nosed Monkey (Rhinopithecus strykeri), 130. Pig-tailed Langur (Simaas concolor), 131. Proboscis Monkey (Nasalis larvatus)

Distribution. NW Vietnam, known only from small forest patches in Ha Giang, Tuyen Quang, Bac Kan, and Thai Nguyen provinces.