GIBBONS IN VIETNAM, LAOS AND CAMBODIA
brownish red: yellow-cheeked gibbon (Nomascus gabriellae) — Extant (resident)
dark purple: northern yellow-cheeked gibbon (Nomascus annamensis) — Extant (resident)
dark brown: northern white-cheeked gibbon (Nomascus leucogenys) — Extant (resident)
middle brown: Northern white-cheeked gibbon — Possibly Extant (resident)
light brown: Northern white-cheeked gibbon — Possibly Extinct
blue: southern white-cheeked gibbon (Nomascus siki) — Extant (resident)
dark bluish green: black crested gibbon(Nomascus concolor) — Extant (resident)
light bluish green: black crested gibbon — Possibly Extant (resident)
light purple: Eastern black crested gibbon (Nomascus nasutus) — Extant (resident)
red: Hainan black crested gibbon (Nomascus hainanus) — Extant (resident)
Gibbons are tree-swinging, small-bodied lesser apes not monkeys. They are the smallest of all apes; are found exclusively in Asia, mostly in India, Southeast Asia, Indonesia and to a lesser extent China; and live primarily in monsoon rain forests, mostly lowland forests. What distinguishes an ape from a monkey is the fact that the former doesn't have a tail. Gibbons are sometimes called “lesser apes" to distinguish them from the "greater apes" —humans, gorillas, chimpanzees and orangutans.
Nomascus (one of the four genuses of gibbon) live in Vietnam, Laos and Cambodia:
Eastern black crested gibbons (Nomascus nasutus, Künckel d'Herculais, 1884) live in northeast Vietnam. They are critically endangered.
Northern white-cheeked gibbons (Nomascus leucogenys, Ogilby, 1840) live in northern Vietnam and northern Laos. They are critically endangered.
Southern white-cheeked gibbons (Nomascus siki, Delacour, 1951) live in Vietnam and Laos.. They are endangered.
Yellow-cheeked gibbons (Nomascus gabriellae, Thomas, 1909) live in Vietnam, Laos, and Cambodia. They are endangered.
Northern buffed-cheeked gibbons (Nomascus annamensis
Thinh et al., 2010 live in Vietnam, Cambodia, and Laos.. They are endangered.
Black crested gibbons (Nomascus concolor, Harlan, 1826) live in China, Laos, and northern Vietnam. There are four subspecies: 1) Tonkin black crested gibbon (Nomascus concolor concolor); 2) Laotian black crested gibbon (Nomascus concolor lu); 3) Central Yunnan black crested gibbon (Nomascus concolor jingdongensis; 4) West Yunnan black crested gibbon (Nomascus concolor furvogaster). They are critically endangered. See Black-Crested Gibbons See GIBBONS IN CHINA factsanddetails.com
Gibbons are kept as pets and found in zoos around the world. Miles and Caldecott reported that Black-crested gibbons are kept as pets in Vietnam when infants are plucked from their mothers. As the infant enters adulthood they become a problem and are often abandoned by their owners. [Source: Tommy Boyd, Animal Diversity Web (ADW) /=]
RELATED ARTICLES:
GIBBONS: CHARACTERISTICS, BEHAVIOR, TREES, SONGS, MOTHERS factsanddetails.com
GIBBONS IN SOUTHEAST ASIA factsanddetails.com
HOOLOCK GIBBONS factsanddetails.com
GIBBONS IN INDONESIA factsanddetails.com
GIBBONS IN CHINA factsanddetails.com
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Yellow-Cheeked Gibbons
Yellow-cheeked gibbons (Nomascus gabriellae) are also called golden-cheeked gibbons, yellow-cheeked crested gibbons, golden-cheeked crested gibbons, red-cheeked, buff-cheeked and buffed-cheeked gibbons. They are found in central and southern Vietnam, southern Laos and eastern Cambodia and are primarily frugivores (fruit eater) but may also be classified as herbivores (primarily eat plants or plants parts). Individuals have also been documented eating shoots, leaves, flowers, and occasionally insects in addition to fruits. [Source: Erin Quist, Animal Diversity Web (ADW) /=]
Yellow-cheeked gibbons are found in tropical evergreen forests, preferring lowland forests, and have rarely been observed above 1,500 meters (4,920 feet). Traditionally, many gibbons, including yellow-cheeked gibbons, were considered members of a single species (Hylobates concolor). Yellow-cheeked gibbons were orginally the only representative of the subgenus Nomascus in the genus, making them a subspecies (H. concolor gabriellae). Recently, vocal characteristics and other features have suggested that yellow-cheeked gibbons should be recognized as a distinct species and the genus Hylobates was split into several genera, including Nomascus.
On the International Union for Conservation of Nature (IUCN) Red List yellow-cheeked gibbons are listed as Endangered. In CITES (Convention on International Trade in Endangered Species of Wild) they are in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. The species is threatened by habitat loss (from development and logging), hunting for food and medicinal parts and military activities. Some of their habitat is in nature reserves and national parks. There are some local anti-hunting laws but they are poorly enforced. Adult gibbons typically live high the canopy region of the forest; potential natural predators such as leopards, clouded leopards, and pythons tend to not venture higher than the lower levels of the forest.
Yellow-Cheeked Gibbon Characteristics
Yellow-cheeked gibbons range in weight from seven to 11 kilograms (15.4 to 24.2 pounds), with their average weight being 8.5 kilograms (18.7 pounds). They range in length from 60 to 80 centimeters (23.6 to 31.5 inches). Sexual Dimorphism (differences between males and females) is present: Males are larger than females. Sexes are colored or patterned differently. [Source:Erin Quist, Animal Diversity Web (ADW) /=]
Erin Quist wrote in Animal Diversity Web: Males have small, light-buff cheek patches that extend to the bottom of the eye and can be slightly separated at the neck. Females of this species are smaller than other gibbon females and have a black border on the ears. Females are generally brownish-yellow in color and can have a slight grayish tint to the darker hairs on the chest, on edges of fingers and toes, and on the outer forearm. Adult females may have slightly red-brown genital hairs, and usually there is a trace of a white fringe around the face. The fur of yellow-cheeked gibbons are very fine. Finally, females are only slightly smaller than males. /=\
Fur coloration changes as animals mature. The timing of the color changes is variable and it may take several months to complete. When a buff-cheeked crested gibbon is born, its coat is bright yellow. Within a few months, the color changes to black within a few months; only the cheek patches remain yellow. During this time, the young resemble adult males in their fur coloration. Males retain this color pattern as they mature, but females revert to a yellowish fur around the time of sexual maturity. /=\
Yellow-Cheeked Gibbon Behavior, Communication and Reproduction
Yellow-cheeked gibbons are arboreal (live mainly in trees), diurnal (active during the daytime), motile (move around as opposed to being stationary), sedentary (remain in the same area), territorial (defend an area within the home range) and social (associates with others of its species; forms social groups). Both males and females perform vocal duets (joint displays, usually between mates, and usually with highly-coordinated sounds) as part of maintaining their territory. The size of their range territory is 20 to 50 hectares.
Yellow-cheeked gibbons are only social with their nuclear family. The male and female and their young are always together. They sleep sitting up. A family sleeps together in prefered sleeping trees. The tight-knit family unit participates in social grooming, which is thought to reinforce the bonds between family members. Territories are generally occupied by family group that defend their territory from intrusions by other gibbons with loud morning songs and by actively chasing intruders from the territory.
Yellow-cheeked gibbons communicate with vision, touch, sound and chemicals usually detected by smelling. They also employ duets (joint displays, usually between mates, and usually with highly-coordinated sounds) to communicate. They sense using vision, touch, sound and chemicals usually detected with smell. [Source: Erin Quist, Animal Diversity Web (ADW) /=]
According to Animal Diversity Web: Mated pairs of yellow-cheeked gibbons typically produce duet songs which consist of coordinated vocal interactions by both partners using sex-specific phrases. Other family members may participate in the song. Solo songs are typically produced by unmated buff-cheeked crested gibbons only. Tactile communication occurs when these animals groom one another, play, or mate. Visual communication signals, such as body postures and facial expressions, are also used by these primates. /=\
Also, yellow-cheeked gibbons have extended fields of skin glands situated in the axillary, sternal, and inguinal areas of the body. The glands produce a reddish secretion and are particularly active under hot temperatures and when the animals are excited. It is thought that the glands may play a role in olfactory communication. The glandular secretion also influences the amount of red visible in the yellowish female fur coloration. /=\
Yellow-cheeked gibbons are monogamous (have one mate at a time). They engage in year-round breeding and breed every two to three years. The interbirth interval tends to be relatively long because females nurse the young for up to two years. The average number of offspring is one. The average gestation period is seven months. The average weaning age is 24 months and the age in which they become independent ranging from six to eight years. There is extensive parental investment by both parents. Females necessarily provide nutrition through nursing the young, but both parents may groom, carry, and protect the immature gibbons. Females and males reach sexual or reproductive maturity at six to eight years. Offspring stay with the family unit up to that time. After this time, they move away to establish territories and families of their own.
Northern White-Cheeked Gibbons
Northern white-cheeked gibbons (Nomascus leucogenys) are also known as white-cheeked gibbons. They are closely related to southern white-cheeked gibbons (Nomascus siki). They were previously considered subspecies of the same species. The females of the two species are virtually indistinguishable in appearance. White-cheeked gibbons was considered a subspecies of crested gibbons until 1989. The main difference between the two species is the “mohawk” tuft at the top of the head of white-cheeked gibbons. Their average lifespan of white-cheeked gibbons in the wild is estimated at 28 years. [Source: Tommy Boyd, Animal Diversity Web (ADW) /=]
White-cheeked gibbons live in the canopy of subtropical rainforests at elevations of 300 to 600 meters (984 to 1968 feet) and hardly ever descend to the forest floor. They live in Laos, Vietnam, and Southern China. In Vietnam, they are found to the southwest of the Song Ma and Song Bo Rivers. A close relative, black-crested gibbons, are found northeast of the Song Ma River and northeast of the Song Bo River. The geographical separation is crucial to distinguishing these two gibbon species because white-cheeked gibbons and black-crested gibbons look very much alike.
A great deal of DNA and molecular research has been done recently on gibbon phylogeny (evolutionary history of a species or group of organisms, and the relationships between them). Tommy Boyd wrote in Animal Diversity Web: Before there was thorough DNA evidence, all white crested gibbons were considered members of a single species Hylobates concolor. Chromosomal evidence that is available today allows scientists to distinguish the white cheeked gibbon as a member of the subgenus Nomascus, which are characterized by having a diploid number of 52 chromosomes. Nomascus is found from southern China to southern Vietnam, and is found on Hainan Island. Fur coloration, anatomical data, and vocal data are also used to identify different species of gibbons. Within the subgenus Nomascus, there are four separate species that include Black-crested gibbons, Yellow-cheeked gibbons, N. sp. cf. nasutus, and N. leucogenys. White-cheeked gibbons have therefore been re-named Nomascus leucogenys. There are also subspecies within each species. For example, recent DNA evidence has distinguished Nomascus leucogenys leucogenys as the northern white-cheeked gibbon and Nomascus leucogenys siki as the southern white-cheeked gibbon. Due to the recent taxonomic advancements using DNA, it is not clear what species is being discussed in much of the older literature. [Source: Tommy Boyd, Animal Diversity Web (ADW) /=]
White-cheeked gibbons are critically endangered. On the International Union for Conservation of Nature (IUCN) Red List they are listed as Critically Endangered. In CITES (Convention on International Trade in Endangered Species of Wild) they are in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. The main threats to white-cheeked gibbons are forest clearing. It has also been documented that in North Vietnam, some people have hunted them for their meat. They may still captured for zoos and the the pet trade. Natural predators, especially of young, may include leopards, clouded leopards, large raptors and owls and pythons.
Northern White-Cheeked Gibbon Characteristics and Food
White-cheeked gibbons have an average weight is 5.7 kilograms (12.56 pounds) and have a head and body length that ranges in length from 45 to 63 centimeters (17.7 to 24.8 inches). Sexual Dimorphism (differences between males and females) is present: sexes are colored or patterned differently but they are similarly sized. According to Animal Diversity Web: All infants are born with cream-colored fur. At two years of age, the infants' fur changes from cream to black, and they develop white patches on their cheeks. At sexual maturity, males stay black with white cheeks. Females turn back to the original cream color and they lose the majority of their white cheek color. [Source: Tommy Boyd, Animal Diversity Web (ADW) /=]
Like all species of gibbons, white-cheeked gibbons do not have tails. They have exceptionally long forelimbs and hindlimbs. Their bodies are built for an arboreal lifestyle. They have an opposable big toe and an opposable thumb. This makes grasping food and holding branches easy. Furthermore, their hands are hook shaped, facilitating brachiation (swinging from tree limb to tree limb using their arms). The body of white-cheeked gibbons is small and they have a remarkably upright posture. Their molar teeth are bunodont and their canines are large and showy. The dental formula is 2/2, 1/1, 2/2, 3/3.
White-cheeked gibbons are primarily frugivorous (fruit eating). They especially enjoy eating the pulp of fruits. They are important seed dispersers for some plants. In general, White-cheeked gibbons eat and forage with their family. Unlike other primates that spend half of the day foraging and the other half of the day slumbering, white-cheeked gibbons search for food throughout the day. Early in the morning, they forage high in the canopy. When the sun begins to heat the canopy, they retreat to lower trees in the understory. In addition to fruit, white-cheeked gibbons also eat leaves, flowers, and insects. The type of food that they eat depends on precipitation. When there is a great deal of precipitation, fruit is plentiful and they do not have to travel far to find food. Conversely, they travel great distances in search of food when there is little rainfall.
Northern White-Cheeked Gibbon Behavior, Calls and Reproduction
White-cheeked gibbons are arboreal (live mainly in trees), scansorial (able to or good at climbing), diurnal (active during the daytime), motile (move around as opposed to being stationary), sedentary (remain in the same area), territorial (defend an area within the home range), social (associates with others of its species; forms social groups), and have dominance hierarchies (ranking systems or pecking orders among members of a long-term social group, where dominance status affects access to resources or mates). While in the trees, white-cheeked gibbons spend a great deal of time eating. The size of their territory ranges from 30 to 40 hectares (75 to 100 acres). They defend this territory. [Source:Tommy Boyd, Animal Diversity Web (ADW) /=]
Tommy Boyd wrote in Animal Diversity Web: White-cheeked gibbons live in small families comprising a male adult and a female adult that mate monogamously. They usually have three to four offspring within the group. There is a hierarchy among the family. The female is dominant followed by her female offspring, male offspring, and the adult male is last. White-cheeked gibbons individuals spend much of their free time playing and grooming. White-cheeked gibbons also use vocalizations throughout the day to signal territory, and they are used in mating rituals.
White-cheeked gibbons sense and communicate using vision, touch, sound and chemicals usually detected with smell. They also employ duets (joint displays, usually between mates, and usually with highly-coordinated sounds) to communicate. Individuals signal territory by using vocalizations. They also use vocalizations in mating behaviors. In order to signal aggression, White-cheeked gibbons resort to the common threat of opening their mouth wide to show their teeth. White-cheeked gibbons spend much of their time grooming and playing. Grooming and playing allow individual gibbons to form bonds. It is also likely that chemical cues, such as pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species), are used to communicate reproductive state.
White-cheeked gibbons are monogamous (have one mate at a time) and breed throughout the year. Females have a 28-day menstrual cycle and give birth to a single offspring once every two to three years. The average gestation period is seven months. After the infant is born, it holds on to its mother for nearly two years. The average weaning age is 24 months and the age in which they become independent ranging from three to eight years and the average time to independence is six years. Females reach sexual or reproductive maturity at five to eight years and males do so at five to eight years. Parental care is not only the duty of the female. Males are also involved. There is an extended period of juvenile learning. During this time offspring play, learn to groom and differentiate between food sources, and acquire knowledge about basic social interactions such as social dominance.
Image Sources: Wikimedia Commons
Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.
Last updated December 2024