Tonkin Snub-Nosed Monkey

Classification and Naming

Guy Dollman named the species in 1912, from a Tonkin specimen.^[3] The type locality is Yen Bay, on the Red River in Vietnam. Some authors later placed it in the genus Pygathrix. Pygathrix is the genus of the red-shanked douc langur. It also holds the gray-shanked douc langur and the black-shanked douc langur. Today the species sits in Rhinopithecus again.

It is one of five Rhinopithecus species.^[4] All five share a strongly turned-up nose. China holds the golden snub-nosed monkey and the black snub-nosed monkey. The gray snub-nosed monkey also lives in China. The Myanmar snub-nosed monkey lives in Myanmar and nearby China. The Tonkin species is the only one found in Vietnam.

The species is monotypic, with no subspecies.^[5] Its Latin name avunculus means a mother's brother, or maternal uncle.^[6] Its Vietnamese name is Vooc Mui Hech. Its name places it among the monkeys starting with T.

Appearance and Size

The Tonkin snub-nosed monkey is smaller and slimmer than its four relatives. It also has longer fingers and toes. Males measure 55 to 65 cm in head and body. Females measure 50 to 54 cm. The male tail runs 82 to 92 cm. The female tail runs 65 to 73 cm. Males weigh about 14 kg, and females about 8.5 kg.

The back and outer limbs are very dark. Hands and feet are black. That dark coat places it among the black monkeys. The head, belly and inner limbs are creamy white. It also counts among the white monkeys. An orange patch marks the throat.

The face is striking. Bluish-white skin rings the eyes and nose. The lips are pink and enlarged. In adults, the nose tip turns up almost to the forehead.^[7] The dark mouth and orange throat stand out in adult males. Two buffy white patches sit on the rump. Infants and young juveniles have been described as gray.

Range and Habitat

The species lives only east of the Red River in northeastern Vietnam. Records once came from several provinces in that region. Only two small forest patches hold records: Khau Ca and Quan Ba.^[8] Both lie in former Ha Giang province. Ha Giang merged into Tuyen Quang province in 2025.^[9]

It lives in evergreen forest on steep limestone karst hills. The Red List gives an elevation range of 200 to 1,200 meters. It depends largely on primary forest. That puts it among the rainforest monkeys of Asia.

Khau Ca forest covers about 1,000 hectares. A 2005 to 2006 study found no water source inside it.

Diet and Feeding

This monkey is a selective feeder. It eats young and mature leaves, fruit, flowers and seeds. The Red List records as many as 52 food plant species. That diet makes it one of the herbivorous monkeys.

One field study ran at Khau Ca from 2005 to 2006. Young leaves made up 42% of its feeding records. Flowers made up about 14%, and young stems 10%. Unripe fruit added about 7%. An earlier, smaller study at Na Hang found more fruit and seeds. There, fruit and seeds made up 62% of the diet.

At Khau Ca, it avoids leaves of the most common trees.^[10] Those leaves carry high levels of phenols and tannins. It prefers leaves rich in water and protein, and low in fiber.

Social Life

Researchers at Khau Ca and Tat Ke saw one-male units. Each held an adult male, several females and their young. Young males that left home formed all-male units. Several units could travel together as larger bands. Bands split and rejoined over time.

One-male units at Khau Ca averaged about 12 animals. Bands there held 22 to 81 animals. The largest band held at least 81 animals.

The species is active by day and lives mostly in trees. Researchers at Khau Ca saw it on the ground seven times. It has no fixed sleeping trees. It usually sleeps 5 to 10 meters above the ground. It moves mainly on all fours along branches.

Reproduction remains poorly documented. One field study found no clearly marked breeding season. It saw more infants in September and October 2005. It also saw more in March and April 2006.

Discovery and Rediscovery

The species was first collected in 1911. In the next 50 to 60 years, it was collected perhaps twice. Some scientists feared it was already extinct. In 1989, it was rediscovered at Na Hang in Tuyen Quang province.

In January 2002, primatologist Le Khac Quyet found the Khau Ca population.^[11] He counted 30 monkeys on his first day. The next day, he saw 50 to 60. Another group turned up in Quan Ba forest in 2007.

Population and Rarity

The Red List assessment dates from November 2015. It was published in 2020 and is flagged as needing an update. It estimated 80 to 100 mature individuals. It estimated about 200 to 250 animals in total. No subpopulation held more than 30 to 35 mature animals.

An April 2015 census confirmed 125 to 130 animals at Khau Ca. Fauna & Flora now puts Khau Ca at around 160 monkeys. No reliable, up-to-date global total exists.

Elsewhere, the news is bad. Na Hang once held the largest known group. Conservation there failed, and that population is likely gone.^[12] At Quan Ba, no confirmed sighting has come since 22 June 2020. A systematic survey there in April 2024 found no significant signs. Thirty-two surveyors walked 731 km during that search. Local loss is possible but not proven.

Khau Ca's monkeys show very little mitochondrial variety.^[13] A 2016 study tested 201 fecal samples there. Their mitochondrial HVI sequences were all identical. Five full mitochondrial genomes showed no variation either. The finding covers mitochondrial DNA only.

Main Threats

Hunting is the most immediate threat. People rarely eat the monkey because its meat tastes foul. Hunters still shoot it for use in traditional medicine. Logging, farming and past gold mining have cut its forest.

A hydroelectric dam on the Gam River hit Na Hang hard. Building began in 2002 and brought about 8,500 workers. Their demand for wild meat raised hunting pressure. At Quan Ba, cardamom grown under the forest canopy damages habitat.

The 2015 assessment concluded the species lost 80% over three generations. That covers roughly 36 to 39 years.

Conservation Status

The Tonkin snub-nosed monkey is Critically Endangered under criteria A2acd+3cd; C1+2a(i). It is also listed on CITES Appendix I. Vietnam has protected the species by law since 1994.

Khau Ca became a species and habitat conservation area in 2009. In 2015, Vietnam merged it into a new national park.^[14] Khau Ca now lies within Du Gia-Dong Van Karst Plateau National Park. A 2024 study confirms its national park protection. Fauna & Flora has supported community patrols there for years. Quan Ba forest still has no conservation designation.

It made nine straight editions of the world's 25 most endangered primates. Those ran from 2000-2002 through 2016-2018.

Common Questions