Overview

Brief Summary

Biology

Kloss's gibbon is an arboreal species, spending most of its time in the canopy. They are active in the day (2) and get around by swinging from branch-to-branch, their long hands forming perfect hooks for grasping the branches (5). They live in groups, consisting of a breeding pair and their offspring, with social grooming helping to maintain bonds (5). These groups defend a territory, with loud bouts of singing serving to proclaim ownership (2). Neighboroughing males chorus before dawn and females after dawn with a 50 second great call (6). As young males and females reach sexual maturity they will leave the family group, with the aim of finding a mate and establishing a new group (5). These gibbons feed mainly on fruit, but will also take flowers and some invertebrates to supplement the diet (5). Males and females form monogamous pairs. A single young is produced after a gestation period of seven to eight months. There is typically a gap of two to three years between each birth (2).
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Description

Both male and female Kloss's gibbons have short, black hair throughout their lives. The chest is broad and the limbs are long (4), which aids in swinging from branch-to-branch, a form of locomotion known as 'brachiation' (5). The thumbs and big toes are also very long, and there is webbing between the digits of the hands and feet (4). There is a sac below the throat which is used to produce calls (5). The muzzle is relatively short, and the hair on the crown lies flat; in infants, however, this hair is erect (4).
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Distribution

Kloss' gibbons, Hylobates klossi, are found in Siberut, Sipura, North Pagai, and South Pagai in the Mentawai Islands, western Sumatra, and Indonesia.

Biogeographic Regions: oriental (Native )

  • Haimoff, E., R. Tilson. 1985. Individuality in the female songs of wild Kloss' gibbons (<>) on Siberut Island, Indonesia. Folia Primatologica, 44: 129-137.
  • Nowak, R. 1999. Walker’s Mammals of the World. Baltimore: The Johns Hopkins University Press.
  • Wisconsin Primate Research Center. 2002. "Kloss' gibbon (Hylobates klossii)" (On-line). Primate Info Network. Accessed March 05, 2003 at http://pin.primate.wisc.edu/factsheets/hylobates_klossii.html.
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Range Description

This species is endemic to the four Mentawai Islands (Siberut, Sipora, North Pagai and South Pagai) off the west coast of Sumatra, Indonesia (Geissmann 1995; Groves 2000; Marshall and Sugardjito 1986).
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Range

Found on North and South Pagi, Sipora and Siberut, islands in the Mentawai group, West Sumatra in Indonesia (2).
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Physical Description

Morphology

Hylobates klossii has long forearms for brachiation. These tail-less, slender primates have dense, glossy, black hair with buttock pads and a large throat sac located under the chin. The throat sac helps to enhance their calls. Females are slightly larger than males, with males weighing about 5.6 kg and females weighing about 5.9 kg. Head and body length ranges from 440 mm to 635 mm.

Average mass: 5.7 kg.

Range length: 440 to 635 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

Average mass: 5900 g.

  • Chivers, D., D. MacDonald. 2001. Gibbons. Pp. 398-403 in The Encyclopedia of Mammals, Vol. 2. New York: Facts on File, Inc..
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Type Information

Type for Hylobates klossii
Catalog Number: USNM 121678
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull; Partial Skeleton
Collector(s): W. Abbott
Year Collected: 1902
Locality: South Pagi Island [= Pulau Pagai Selatan], Sikakap Strait [= Selat Sikakap], Sumatra, Sumatera Barat, Indonesia, Asia
  • Type: Miller, G. S. 1903 Nov 06. Smithsonian Miscellaneous Collections. 45: 70.
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Ecology

Habitat

Kloss' gibbons can be found in the upper canopy of semi deciduous monsoon forests and tropical evergreen forests.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: rainforest

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Habitat and Ecology

Habitat and Ecology
This species is arboreal, diurnal, and omnivorous, though predominantly frugivorous (Whitten 1982a). Although disturbance levels in H. klossii habitat on the different islands are variable, a recent survey detected similar population densities in un-logged forests, forests logged 10 years ago, and those logged 20 years ago (Whittaker 2005; Paciulli 2004).

Gibbons in the Siberut area studied by both Tenaza (1974, 1975) and Tilson (1980) had unusually small average home ranges of 7-11 ha. A gibbon group studied in a different area on Siberut had a home range size of 32 ha, similar to that in other species of the genus Hylobates (Whitten 1980, 1982b).

Systems
  • Terrestrial
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Inhabits tropical rainforest (2) and monsoon forest (5).
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Trophic Strategy

Kloss' gibbons are primarily frugivorous, preferring to eat fruits with high sugar content, such as figs, 72 percent of the time. They will also consume flowers, eggs, small vertebrates, and insects 25 percent of the time. This species tends to spend time apart from members of its own group while feeding -- up to 50 meters at times. In the wild, Kloss' gibbons have been observed to spend a large amount of feeding time searching for arthropods.

Animal Foods: birds; mammals; amphibians; reptiles; eggs; insects

Plant Foods: leaves; fruit; flowers

Primary Diet: herbivore (Frugivore )

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Associations

Kloss' gibbons act as important seed dispersers in their forest ecosystems.

Ecosystem Impact: disperses seeds

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Predators of Kloss' gibbons include leopards, snakes, and large birds of prey. Their social system means that many individuals are vigilant and will warn other members of the troup of impending danger.

Known Predators:

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Known predators

Hylobates klossii is prey of:
Serpentes
Panthera pardus
Falconiformes

This list may not be complete but is based on published studies.
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Known prey organisms

Hylobates klossii preys on:
Insecta
Amphibia
Reptilia
Aves
Mammalia

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

Kloss' gibbons are known for their magnificent vocal communication. Females tend to have the most distinctive calls with a slow rise and fall, interrupted by a trill sequence. Male calls consist of moans and "quiver-hoots". Males will sing solos from 10 minutes up to 2 hours in both the pre- and post-dawn hours. Often, breeding pairs form duets together 2 to 3 hours after dawn, with the female's contribution lasting about 15 minutes. Occasionally, the young will join in the duet of their parents. It has been hypothesized that the duets are a means of intimidating neighbors to defend their territory and/or as a way to maintain social organization. Studies have shown that both males and females can be identified by the individuality of their calls, with each animal having its own unique voice.

Kloss' gibbons also use chemical, tactile, and visual modes of communication. Social grooming is an important form of social bonding and facial and body gestures are important ways of communicating among gibbons. Another important interaction is play behavior centered on the infant.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: duets ; choruses

Perception Channels: visual ; tactile ; acoustic ; chemical

  • Cowlishaw, G., D. MacDonald. 2001. Defense by Singing: Great calls and Song Bouts of the Gibbons. Pp. 404-405 in The Encyclopedia of Mammals, Vol. 2. New York: Facts on File, Inc..
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Life Expectancy

The lifespan of Kloss' gibbons may be as long as 25 years. Other members of the genus Hylobates are known to live upwards of 44 years in captivity.

Range lifespan

Status: wild:
25 (high) years.

Range lifespan

Status: captivity:
37 (high) years.

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Lifespan, longevity, and ageing

Maximum longevity: 37 years (captivity) Observations: One wild born animal was about 37 years old and still alive in captivity (Richard Weigl 2005).
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Reproduction

Kloss' gibbons are monogamous. Mated pairs of males and females, with their young, form the basic social unit.

Mating System: monogamous

The gestation period of H. klossii lasts 7 to 8 months, with one infant born every 2 to 3 years. Weaning occurs early in the second year of life. Kloss' gibbons reach sexual maturity at 6 to 7 years of age. Young do not usually disperse from their family unit until they reach late adolescence. The testicular sac in males is covered by short, sparse hairs. In females, the labia majora is prominent, making it difficult to distinguish males from females in the field.

Breeding interval: One infant is born every 2 to 3 years to an individual female.

Breeding season: These animals breed throughout the year.

Average number of offspring: 1.

Range gestation period: 7 to 8 months.

Range weaning age: 24 (high) months.

Range age at sexual or reproductive maturity (female): 6 to 7 years.

Range age at sexual or reproductive maturity (male): 6 to 7 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Average number of offspring: 1.

Males and females participate in caring for the young. Around the time of adolescence, males and females will disperse from their parent's group. Often parents will assist dispersing adolescents in obtaining territory by accompanying the young into new territory and threatening those occupying the new area.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning

  • Chivers, D., D. MacDonald. 2001. Gibbons. Pp. 398-403 in The Encyclopedia of Mammals, Vol. 2. New York: Facts on File, Inc..
  • Haimoff, E., R. Tilson. 1985. Individuality in the female songs of wild Kloss' gibbons (<>) on Siberut Island, Indonesia. Folia Primatologica, 44: 129-137.
  • Nowak, R. 1999. Walker’s Mammals of the World. Baltimore: The Johns Hopkins University Press.
  • Parker, S. 1990. Old World Primates. Pp. 350-355 in Grzimek’s Encyclopedia of Mammals, Vol. 2. New York: McGraw-Hill Publishing Company.
  • Whitten, A. 1982. Diet and feeding behavior of Kloss gibbons on Siberut Island, Indonesia. Folia Primatologica, 37: 177-208.
  • Wisconsin Primate Research Center. 2002. "Kloss' gibbon (Hylobates klossii)" (On-line). Primate Info Network. Accessed March 05, 2003 at http://pin.primate.wisc.edu/factsheets/hylobates_klossii.html.
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Conservation

Conservation Status

The IUCN lists H. klossii as vulnerable due to the extent of occurrence and/or quality of habitat. The status of H. klossii is threatened because of an increased human population, hunting, and deforestation. CITES lists H. klossii on their Appendix I list.

US Federal List: no special status

CITES: appendix i

IUCN Red List of Threatened Species: endangered

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IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
A2cd

Version
3.1

Year Assessed
2008

Assessor/s
Whittaker, D. & Geissmann, T.

Reviewer/s
Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)

Contributor/s

Justification
Listed as Endangered due to a past and continued populations decline, estimated at more that 50% over the past 45 years (approximately 3 generations) due to hunting and loss of habitat.

History
  • 2000
    Vulnerable
  • 1996
    Vulnerable
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Vulnerable
    (IUCN Conservation Monitoring Centre 1986)
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Status

Classified as Vulnerable (VU A1c+2c, B1+2ac) on the IUCN Red List 2004 (1). Listed in Appendix I of CITES (3).
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Population

Population
Whittaker (2005a,b) gathered population estimates on all four Mentawai Islands, using loud-call monitoring and forested area estimates to census the animals. The species population is estimated at 20,000 to 25,000 individuals remaining on the Mentawai Islands, where they are endemic (Whittaker 2005b, 2006), which amounts to a reduction in numbers of up to 50% since the last survey in 1980 (World Wildlife Fund 1980; MacKinnon 1986, 1987). Throughout the Mentawai Islands, density averaged 12 individuals/km2 (Whittaker 2005a, b). The largest remaining population, 13,000-15,000 individuals, is found in Siberut National Park (Whittaker 2005b, 2006).

Population Trend
Decreasing
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Threats

Major Threats
This species is threatened mainly by hunting and commercial logging (Whittaker 2006). It is also threatened by conversion to oil palm plantations, and forest clearing and product extraction by local people (Whittaker 2006). Recently, hunting pressure has increased because of increased access to remote areas due to logging roads and tracks, as well as the replacement of bows and arrows with .177 caliber air rifles (Whittaker 2006). Also, local rituals and taboos which formerly regulated hunting have been replaced by Christianity (Whittaker 2006). The pet trade is also a threat to this species (Whittaker 2006). Although this may be a greater threat to this species than to other gibbons (D. Whittaker pers. comm.), it is rarely seen in the pet-trade in Java (Nijman 2005).

The extent of the threats from logging, hunting, and the pet trade faced by this species varies depending on location. The very large population in Siberut National Park, on central Siberut, lives in a protected area but is subject to moderate hunting pressure from local people. In the Peleonan forest, northern Siberut, the habitat was logged 20 years prior but faces low hunting pressure. This area is significant because four of the endemic Mentawai primates (H. klossii, Simias concolor, Presbytis potenziani and Macaca siberu) exist here in high densities. Populations in Saureinu, Sipora are subject to traditional use by locals but limited logging. In South Pagai, forest plots are selectively logged but there is high hunting pressure. Animals on North Pagai were not censused, but logging and hunting occurs there as well (Whittaker 2005b).
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The main threat facing these gibbons is habitat destruction and degradation caused by human activities in the area (1). Hunting is also a problem, which worsens as habitat destruction continues, as it allows greater access into the forest (2).
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Management

Conservation Actions

Conservation Actions
This species is listed on CITES Appendix I, and is protected by Indonesian law. More than half of the remaining Kloss's gibbons reside in Siberut National Park, a government protected area. Whittaker (2005b, 2006) suggested the following conservation actions: 1) increased protection for Siberut National Park, which currently lacks enforcement, 2) formal protection of the Peleonan forest in North Siberut, which is home to unusually high primate populations and is easily accessible, 3) protection of areas in the Pagai Islands by cooperating with a logging corporation that has practiced sustainable logging technique there since 1971, 4) conservation education, especially regarding hunting, and 5) the development of alternative economic models for the local people to reduce the likelihood of selling off their lands to logging companies (Whittaker 2006).
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Conservation

Kloss's gibbon is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which prohibits international trade in this species (3).
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Relevance to Humans and Ecosystems

Benefits

There are no known negative impacts of Kloss' gibbons.

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Kloss' gibbons are a potential source of ecotourism dollars, as well as being important parts of a healthy ecosystem from which humans benefit.

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Wikipedia

Kloss's gibbon

Kloss's gibbon (Hylobates klossii), also known as the Mentawai gibbon or the bilou, is a primate in the gibbon family, Hylobatidae. It is identifiable in that it is all black,[3] resembling the Siamang with its black fur, but is considerably smaller and lacks the Siamang's distinctive throat pouch. Kloss's gibbon reaches a size 44 to 63 cm and weigh at most 6 kg. As is the case for all gibbons, they have long arms and no tail.

Kloss's gibbon exclusively lives on the Mentawai Islands that lie to the west of Sumatra.[1] It is a diurnal inhabitant of the rain forest that hangs in the trees from its long arms and rarely comes to the ground. Like all species of gibbons it lives together in pairs that stake out a territory from approximately 20 to 30 hectares of size. This area is defended vehemently against other gibbons. Its diet consists mainly of fruits, occasionally also eating different plant parts, bird eggs, insects and small vertebrates.

The singing of the female Kloss's gibbon is considered the most beautiful of all the gibbons' songs. Unlike most other gibbon species (except for the Javan silvery gibbon, Hylobates moloch), Kloss's gibbon males and females do not sing duets. Males typically sing in the hour before sunrise, while an all-female chorus occurs after sunrise. The singing of the gibbons serves to warn off other animals from their territory, and possibly to strengthen the family bonds.

The reproductive cycle of Kloss's gibbon is similar to that of other gibbons. Every two to three years the female may give birth to a single young (with a gestation period of seven months). The young is weaned in the middle of its second year, and is fully mature in about seven years. Their life expectancy is about 25 years in the wild, and up to 40 years in captivity.

References[edit]

  1. ^ a b Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. p. 179. OCLC 62265494. ISBN 0-801-88221-4. 
  2. ^ Whittaker, D. & Geissmann, T. (2008). Hylobates klossii. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 4 January 2009.
  3. ^ Kloss Gibbon at the zoo
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