Nomascus nasutus

Eastern Black Crested Gibbon (Scientific name: Nomascus nasutus) English Cao-vit Gibbon, Eastern Black Crested Gibbon, Vietnamese vượn cao vít, vượn đen,. The Eastern Black Crested Gibbon (Nomascus nasutus) has been recognized as an independent species by different authoritative biological departments. It belongs to the order Primates, family Gibbon, genus Nomascus. The species was once considered to be the same species as Hainan gibbon (N.hainanus) or as a subspecies of black crested gibbon (N.concolor). Based on differences in vocalization and fur color and genetic evidence, the Eastern Black Crested Gibbon is considered to be a species different from Hainan gibbon and black crested gibbon (Feng et al., 2014).

The Eastern Black Crested Gibbon is a diurnal animal, accustomed to going to bed early and getting up early. After sunrise every day, the Eastern Black Crested Gibbon will leave the overnight tree to start the day's activities, and will enter the overnight tree one and a half hours before sunset. They prefer to choose some tall trees to spend the night. Avoiding natural enemies, wind and heat preservation are the main factors that affect their choice of trees for the night. A family often has hundreds of different trees for the night, and some trees for the night are used repeatedly for dozens of times, but they rarely use the same tree for the night for two consecutive nights. At night, different individuals in a family often sleep in different trees, and minors are used to rest with their mothers. They stay in the tree for 13-14 hours a day, and have developed very good hygiene habits. They usually defecate after leaving the tree for the night. In order to promote mutual affection and maintain harmonious family relationships, individuals in the group often comb their hair on the tree for the night.

The Eastern Black-crested Gibbon is a singer in the karst forest. The adult males and adult females in the family group can cooperate with each other to produce a beautiful duet. The duet begins with the adult male's initial syllables and simple repeated syllables. As the call progresses, the number of simple repeated syllables in the male's call sequence increases, and the structure of the regulating syllables becomes complex. At the climax, the female makes an exciting call to cooperate with the male to form an exciting call sequence. Their songs are extremely penetrating and can spread 1-2 kilometers. Every sunrise, the eye-catching monkey calls can often be heard in the morning light, "Hu-Hu-Hu, Hu, Hu", clear and loud, one after another; sometimes mixed with low response sounds "Wu-Wu", interlaced and noisy. The duet structure of the paired black gibbons is stable, dominated by males, and has extremely high male-female specificity - there is no overlap in the calls of the two sexes in terms of tone or syllables. Although the calls of gibbons are determined by genes, and each type of gibbon has its own fixed calling pattern, as the environment changes, its calls will also show a certain plasticity, which will be reflected in the differences between individuals. These duets are inferred to have the functions of defending territory, defending food resources, attracting mates, strengthening pairing relationships, cohesion of groups, and regulating inter-group relationships. When defending the territory, the Eastern Black-crested Gibbon prefers to sing in the center of the home range, which is considered to be an adaptation to the karst environment in order to better convey the information carried in the sound.

The Eastern Black-crested Gibbon feeds on 81 species of plants and a small number of animals, especially the fruits of the large-leaved water fig, the big green tree and the small-leaved fig. Lianas are also important food sources for them. From May to September, they feed on the fruits of the hairy-veined cliff creeper and its young leaves throughout the year. The Eastern Black-crested Gibbon has a clear seasonal foraging strategy. In the rainy season, the Eastern Black-crested Gibbon will also give priority to eating fruits, spending more than 60% of the time eating fruits and less than 2% of the time eating leaves and buds. However, in the dry season, the time of eating leaves and buds exceeds 50%, and March is the peak of eating leaves and buds, which can even reach 95%. Overall, fruits account for 52% of the Eastern Black Crested Gibbons' annual diet, followed by 35% of leaves and buds, and 9% of animal food. Eastern Black Crested Gibbons are very frugal and do not waste food. When eating, they only pick ripe fruits to fill their stomachs, and will not destroy those unripe fruits. Similar to the Western Black Crested Gibbons living in Wuliang Mountain, Yunnan, Eastern Black Crested Gibbons occasionally prey on small mammals such as squirrels.

Eastern black-crested gibbons live in a stable family group of one male and two females. Both females in the group can reproduce. The relationship between the females in the group is harmonious. They often groom each other and feed together. There are rarely conflicts. Adult females generally give birth once every three years, and there is no record of twins. The underage offspring of the two females also live in the group, and the group size is generally between 5-9. The baby monkey will leave the mother and start to move alone at the age of 4 and a half months, start to eat solid food at the age of 8 months, start to groom other family members at the age of 11 months, and be weaned at the age of 24 months. Around the age of 8, both sexes may migrate from their original families, but males are more likely to leave home than females. "Infanticide" is common among primates. It means that the newly promoted adult male sometimes kills infants and young individuals in the group, prompting the females to enter the estrus period quickly so that the new male can obtain his own offspring in the shortest time. Long-term field observations have found that whenever the adult males in the Eastern Black Crested Gibbon family group are replaced, the infant monkey offspring of the former male are often in danger. The former male who was replaced will leave the original group and disappear.

Due to poaching and habitat loss, the population of this species has dropped sharply. It was once thought to be extinct in China since the 1950s, and there was no definite news about the distribution of this species in Vietnam after the 1960s. Fortunately, investigators rediscovered the species in the karst forests of Chongqing County, Cao Bang Province, Vietnam and Jingxi City, Guangxi Zhuang Autonomous Region, China in 2002 and 2006 respectively. The return of the Eastern Black Crested Gibbon, which had "disappeared" for nearly half a century, also became a sensational scientific discovery in the international conservation biology community. The rediscovery of the Eastern Black Crested Gibbon has given humans the opportunity to re-recognize and understand them. Since 2007, a scientific research team led by Professor Fan Pengfei of Sun Yat-sen University has begun a long-term study on the foraging, overnight stay, reproduction, singing, social system, and protection of the Eastern Black Crested Gibbon in a small karst forest at the junction of Jingxi, China and Cao Bang, Vietnam. People's understanding of the Eastern Black Crested Gibbon basically comes from their day-to-day observation and recording of 3-5 family groups. October 24, 2022 is International Gibbon Day. After the cooperation between China and Vietnam to restore the habitat of the Eastern Black Crested Gibbon, the number of Eastern Black Crested Gibbons in the reserve has increased to 5 groups of 35.

Listed in the "IUCN Red List of Threatened Species" (IUCN) 2015 ver3.1-Critically Endangered (CR).

Listed in Appendix I, Appendix II and Appendix III of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) 2019 Edition Appendix II.

Listed in China's "National Key Protected Wildlife List" (February 5, 2021) Level 1.

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Distributed in Yunnan, China and Vietnam. The population is restricted to a small area of ​​karst forest, about 2,500 ha, in Trung Khanh District, northern Cao Bang Province, Vietnam, and adjacent forests in Jingxi County, Guangxi, China. Other surveys in Vietnam at the site of historical records have not returned other populations, so it is considered extinct in the rest of its former range, although some individuals may remain in isolated pockets of inaccessible karst forest (Rawson et al., 2011).
Historically, the Eastern Black-crowned Longbreast was distributed from southern China to northern Vietnam, extending south to the Red River. The species' range once extended from Halong Bay southward to the Red River Delta, and formerly lived in adjacent areas of southeastern China (Guangdong and Guangxi Provinces), but is thought to have almost completely disappeared from there in the 1950s (Geissmann et al., 2000).
It mainly inhabits tropical rainforests and southern subtropic

The Eastern Black-crested Gibbon is a medium-sized ape with a strong body, weighing 7-10 kg and a body length of 45-64 cm. Adult individuals have obvious hair color sexual dimorphism. Male individuals are covered with black hair from birth to adulthood. Male apes have short and upright crown-shaped tufts of hair on their heads, which resemble black crowns. Female individuals turn yellow-brown when they approach adulthood. The hair color of adult females is mainly bright yellow-brown, but can also be gray-yellow, brown-yellow or orange-yellow. There are prismatic or polygonal black-brown crown spots on the top of the head, which can extend from the shoulders to the back, and there is a very obvious circle of white hair on the face. The legs are very short, but the arms are extremely long. The forelimbs are obviously longer than the hind limbs. Its arm span can reach more than one meter. It mainly moves in the forest by alternating swinging and climbing with its arms. The hair is short a