Black Crested Gibbon, Nomascus concolor

BLACK CRESTED GIBBON

Nomascus concolor

Geographic Distribution and Habitat

Black crested gibbons have lost 75% of their habitat to hunting and human encroachment, giving this small ape the unfortunate status of being one of the world’s most endangered primates. Today, the black crested gibbon survives in remote, largely inaccessible pockets of sub-tropical and montane evergreen, semi-evergreen, and deciduous forests in China, Lao People’s Democratic Republic (Lao PDR), and northern Vietnam.

TAXONOMIC NOTE

As one of the 18 species that comprise the gibbon family of small apes, the black crested gibbon is thought to incorporate four different subspecies, each found in separate geographic regions: 

  • In China’s Yunnan province, two subspecies have been identified:
    • the central Yunnan (N. c. jingdongensis)
    • the west Yunnan black crested gibbon (N. c. furvogaster)
  • The Laotian black crested gibbon (N. c. lu) is found in Laos
  • The Tonkin black crested gibbon (N. c. concolor) is found in northern Vietnam.

It’s worth noting that another gibbon species, the Critically Endangered Hainan black crested gibbon (Nomascus hainanus), has been, at times, considered a subspecies of N. concolor, but most now recognize it as a distinct species for its unique vocalizations and fur color. 

Black crested gibbon range, IUCN 2020

Size, Weight, and Lifespan

Black crested gibbons are excellent acrobatic athletes, with ultra-light frames that enable them to seemingly fly through the canopy and forage for fruit even on the thinnest of branches. On average, they weigh only 17.6 lb (8 kg) at full maturity, with a head-body length of 19.6 in (50 cm). Like other apes, gibbons do not have tails.

Primatologists believe that black crested gibbons can live up to 30 years in the wild, a life expectancy thought to be shared by all gibbon species.

Appearance

At first glance, male and female black crested gibbons look so dissimilar one might think they belonged to two distinct gibbon species. Unlike the adult female, who wears a golden-buff coat, the male black crested gibbon has deep black fur with white cheeks. Upon closer examination, however, one can see the similarities between the sexes—especially in the tuft of longer black hair crowning their heads, a distinguishing feature that earned the black crested gibbon species its moniker. Both also share black, nearly hairless faces. They have a small ape’s slender build, with hands and feet designed for grasping branches and long, lanky limbs (the arms are about twice the length of the body).

The marked visual differences seen with black crested gibbons is known as sexual dichromatism and develops over time; as the female matures, her fur will change from a youth’s black to the rich golden buff of adulthood.

Female black crested gibbon
Photo credit: ©@huangmingpan/ iNaturalist/Creative Commons
​Diet

A frugivore (fruit-eater), the black crested gibbon prefers sugar-rich fruits such as figs, but she will forage for leaves, flowers, insects, eggs, and other small organisms when the supply of her first-choice foods becomes scarce, especially during the dry season.

Behavior and Lifestyle

This gibbon family of small apes is under-researched, and much is still not known about their social life and cognitive abilities. Specific data on the black crested gibbon species are also limited: for example, it wasn’t until 2007 that the first field data on the Laotian black crested gibbon was published, some 68 years after the subspecies was first identified.

One behavior well associated with all gibbons, including the black crested variety, is theirs mastery of brachiation—that is, their ability to use their long arms to energetically swing between branches in the tree canopy, sometimes spanning distances of up to 50 feet (15 m) and reaching swift speeds of 35 mph (56 km/h). Despite this arboreal (tree-dwelling) skill, black crested gibbons can and do walk upright both on the ground and on branches in the canopy.

Fun Facts

The Ape superfamily comprises only two families: The great apes (also known as Hominidae) and the gibbons (Hylobatidae). Although the gibbons are known as “small apes” or “the lesser ape,” they comprise the largest group of all apes in 19 species within its family. 

The black crested gibbon’s Latin name, Hylobates, means “dweller in the trees”—a perfect descriptor for this arboreal small ape.

Daily Life and Group Dynamics

Living in small family groups of six to eight, black crested gibbons are active during the day, foraging for fruit and other foods. At night, they seek tall, thick trees with large crowns for sleeping. Researchers note that they choose sleeping trees that afford access to food and quick escape paths. They are territorial by nature, but scientists note that they retreat from human encroachment in their habitat, a factor thought to contribute to their limited range today.

In China’s Central Yunnan, primatologists found that the black crested gibbon sleeps with their long arms wrapped around bent knees and head leaning down. Some, but not all, individuals seek the same place in the same tree each night for sleep.

Communication

As with many gibbons, black crested gibbons are equipped with a special throat sac below the chin that helps amplify their melodic songs and yodeling calls. So unique are these songs that they resemble a rainforest bird’s calls and bear no similarity to any other non-gibbon primate’s vocalizations.

Researchers have studied the songs of black crested gibbons to understand how the songs can help identify differences between sexes, as well as between other crested gibbon species and subspecies, each of which is thought to have its own vocal patterns and notes. Males and females perform haunting duets, often at dawn and initiated from a tall tree on a high hill, in which the male grunts, squeals, and whistles, while the female sings out in rising notes and twitters. Whether performed alone or in pairs, these elaborate songs are thought to play an essential role in defending territories, protecting food resources, mating, and strengthening bonds between pairs and within a family.

In addition to vocalizations, black crested gibbons communicate through physical interactions and facial expressions. 

Reproduction and Family

While most black crested gibbons are monogamous, with family life revolving around a single male-female pairing, some research suggests that this species may be unique among gibbons by engaging in polygynous mating, with documented occurrences of multiple females living within a single breeding group.

For most black crested gibbons, however, a monogamous male and female will pair and reproduce every two to three years. A newborn infant will cling to her mother’s belly during the first few months, weaning by two years of age. Both male and female infants are born with white fur at birth, but the coat changes to black at around one year. A female’s coat changes again to golden-buff as she reaches early adulthood around eight years old. Both males and females leave their natal group to mate and form a new family unit.

Female and infant
Photo credit: © Ran Dai/iNaturalist/Creative Commons
Ecological Role

As fruit-loving primates, black crested gibbons help disperse seeds throughout their habitats through consumption and excretion, which is critical to regenerating rapidly disappearing forests.

Conservation Status and Threats

With no more than 2,000 individuals remaining in the wild, the black crested gibbon is Critically Endangered, according to the International Union for Conservation of Nature (IUCN, 2015). In the last 45 years—a span of three generations—the species has severely declined by over 80% due to habitat loss and hunting. Region-specific threats include:

  • In Lao PDR, locals hunt the black crested gibbons for food, as well as for the pet and medicine trades, despite taboos against hunting gibbons.
  • In Vietnam, habitat destruction and bushmeat hunting represent the biggest threats.
Conservation Efforts

Black crested gibbons are listed on Appendix I of Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), making all commercial trade of this species illegal.

To help prevent further habitat loss, China has established several nature preserves to protect the black crested gibbon’s range. Similarly, Lao PDR has established two protected areas, Nam Ha National Biodiversity Conservation Area and Nam Kan National Biodiversity Conservation Area; officials have also established steep fines and gun control measures to discourage opportunistic hunting. In addition, the non-profit Gibbon Conservation Alliance formed in 2003 to help promote gibbon conservation, funding, research, awareness, and education.

Several tourism-based conservation projects have formed to help the plight of all gibbons. One such group is the Gibbon Experience in Lao PDR, which helps raise awareness by inviting visitors to observe black crested gibbons in the Nam Kan National Biodiversity Conservation Area. The work provides full-time jobs to over 120 people.

References:
  • http://www.arkive.org/black-crested-gibbon/nomascus-concolor/
  • http://animaldiversity.org/accounts/Nomascus_concolor/
  • https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-11-36
  • http://www.bbc.co.uk/nature/life/Black_Crested_Gibbon
  • http://www.gibbonconservation.org/index_engl/
  • http://www.gibbons.de/main/papers/pdf_files/2007nam-kan-survey.pdf
  • https://www.gibbonexperience.org/black-crested-gibbon-nomascus-concolor/
  • http://www.iucnredlist.org/details/39775/0
  • http://www.waza.org/en/zoo/visit-the-zoo/primates-1254385523/apes-1254385523/nomascus-hylobates-concolor

Written by Christine Regan Davi, December 2017