White-handed gibbon

White-handed gibbon
White-handed gibbon pair ( Hylobates lar ), light and dark colored morphs
Systematics
Partial order : Monkey (anthropoidea) without rank: Old World Monkey (Catarrhini) Superfamily : Human (Hominoidea) Family : Gibbons (Hylobatidae) Genre : Little Gibbons ( Hylobates ) Type : White-handed gibbon
Scientific name
Hylobates lar
( Linnaeus , 1771)

The handed gibbon or Lar ( Hylobates lar ) is a primate of the family of gibbons (Hylobatidae). It is one of the most famous gibbon species and is often seen in German zoos.

features

White-handed gibbon skeleton

Skull of a white-handed gibbon (Collection Museum Wiesbaden )

White-handed gibbons reach an average body length of 41 cm and an average weight of 4–7 kg (males) and 3–6 kg (females). This information comes from publications by A. Schultz from 1933 and 1973. The weight information is from the type series of the subspecies H. l. Carpenteri , which presumably includes some not fully grown individuals. Measurements from southern China by H. l. yunnanensis were published by S. Ma and colleagues in 1988. On average, the four males and one female had a head torso length of 49 cm (ranged from 44-57 cm) and a weight of 7 kg (ranged from 5-8 kg). Weights of the subspecies from Sumatra H. l. vestitus were published by C. Kloss in 1929 : males 4-5 kg, females 5 kg.

The white-handed gibbon has two main fur morphs - dark (brown to black) and pale (cream-colored to reddish-yellow-brown) - that are not related to gender or age, although the exact color tones vary depending on the region. In museum collections, specimens by H. l. vestitus is quite light brown (like the bright morphs of H. l. entelloides ) and it appears that this subspecies does not show any color polymorphism, but this has yet to be confirmed in wild populations. All white-hand gibbons have a bare black face, framed by a ring of whitish fur and white fur on the tops of the hands and feet. The head hair is directed backwards like a fan and is not elongated or covers the ears at the side. Adult males have a black head of hair in the pubic area. Both sexes are almost the same size. The coat color is very variable on the Malay Peninsula (from dark brown to yellow-brown), but to the north the individuals are either very dark (black) or very pale (cream-colored) with no intermediate forms. These extremes are gender-independent, unlike neighboring species of the genera Hoolock and Nomascus .

Sitting white-hand gibbon

distribution and habitat

Distribution area (green) of the white-handed gibbon

The distribution area of ​​the white-handed gibbon extends from southern China ( Yunnan ) and eastern Myanmar over Thailand over the entire Malay Peninsula southwards with the exception of a small area in the Thai- Malaysian border area, where the black-handed gibbon ( H. agilis ) represents the species. In addition, the white-handed gibbon can also be found in the north of the island of Sumatra . The four subspecies divide the range as follows:

• H. l. lar (Linnaeus, 1771) - Malay Peninsula, from the Perak River to the Mudah River
• H. l. carpenteri Groves, 1968 - East Myanmar, Northwest Laos and Northwest Thailand
• H. l. entelloides I. Geoffroy Saint-Hilaire, 1842 - South Myanmar and Southwest Thailand
• H. l. vestitus GS Miller, 1942 - North Sumatra, northwest of Lake Toba and the Singkil River
• H. l. yunnanensis Ma & Wang, 1986 - South China (Southwest Yunnan), northernmost subspecies, originally between the Nujiang (= Saluen) and the Lancangjiang (= Mekong) Rivers in Cangyuan , Menglian and Ximeng , since the 1960s only on the Nangun River at heights of Occurring 1000 to 1500 m, but now probably extinct there

The white-handed gibbon forms a narrow hybrid zone with the cap gibbon ( H. pileatus ) in the Khao Yai National Park in central Thailand and the black-handed gibbon ( H. agilis ) on the Malay Peninsula (attributed to the creation of an artificial lake in the 1970s) and is extensive on the Malay Peninsula and North Sumatra with the Siamang ( Symphalangus syndactylus ) sympatric .

The white-handed gibbon mostly lives in tropical lowland rainforests with dipterocarp trees. Mixed deciduous bamboo forests, evergreen, semi-evergreen and moist evergreen forests and even moor and swamp forests also represent the habitat of the species. Most of these forests are at altitudes below 1200 m. The white-handed gibbon prefers the highest levels of untouched primary forests , but is also found in secondary and selectively cleared forests. The average height of the forage trees in the Khao Yai National Park in Thailand is 23 m.

Way of life

Activity pattern

White-handed gibbons when swinging (brachiation)

White-handed gibbons are diurnal tree dwellers. On average, they spend their day eating (33%), resting (26%), hiking (24%), social activities (11%), communication (4%) and encounters between groups (2%), but the values ​​change significantly over the course of a year. Foraging and resting take up most of the day. White-handed gibbons in Thailand are active an average of 8 hours a day, leave their sleeping places during sunrise and go to their sleeping trees an average of 3 hours before sunset. When the morning is clear, the adult male makes his solo calls - usually from the sleeping tree. At sunrise, when all group members are awake, they poop and urinate while hanging on branches. Then the group moves towards a forage tree. Usually there are duets from the couple before noon. The rest of the day is alternately filled with eating and looking for new food trees. When fruit is scarce, white-handed gibbons spend more time on social activities and vice versa. One group takes more than an hour of rest during a day and dedicates itself to social activities. White-handed gibbons try to avoid being noticed where and when they come to their sleeping places in order to presumably reduce the risk of being eaten. Often the highest trees in the area are chosen as sleeping places, if possible on steep slopes and cliffs. During the cool season, groups of white-handed gibbons spend several hours a day, often in large fig trees .

Social behavior

Generally speaking, white-handed gibbons live continuously in monogamous pairs with up to four pups per group, but every now and then they form polygamous groups (one female and two adult males). Sometimes sexual relationships extend beyond those with the cohabiting partner and polygamous pairings have also been observed. Long-term data shows that females are likely to spend their lives in different types of groups (e.g. with one or more males). In the case of additional pairings in females, the frequency of copulations with their own partner is still higher than with other males. Population censuses in the Khao Yai National Park from 1992 to 2007 showed that an average of 76% of the animals there lived monogamous and 21% lived in groups with one female and several males (excluding groups with several male young animals). Groups with one male and multiple females are rare (1%) and the only evidence in Khao Yai showed that one of the females was a cap gibbon ( H. pileatus ) and not a white-handed gibbon. In the case of single pair formation, changes can occur due to leaving (often for another partner), replacement of a partner by an individual from a neighboring territory, disappearance or death of a partner. Changes in couple make-up are common due to disease, lack of food sources, and fragmented and isolated habitats. Pair bonds usually last a lifetime. The average group size increases with latitude and shows that group size is not a useful way of differentiating gibbon species. This reflects the general trend of increasing the birth rate with latitude in many vertebrate groups. On the Malay Peninsula, groups contain an average of two to three individuals, three in central Thailand and four in northern Thailand. The territory size ranges from 12–54 ha., On average approx. 40 ha., With maximum values ​​on the Malay Peninsula (44–54 ha.) And lowest values ​​in the Khao Yai National Park in the north of the distribution area (approx. 16 ha.). Although the territories of different groups often overlap, there is a core area, about 76% of the territory, which is defended against other groups.

On average, white-handed gibbons travel 1,400 m per day, but there are significant differences between the areas studied. When fruits are abundant, the daily distance traveled is reduced. Groups are usually led by females, but males sometimes take on this role too. Their main task, however, is the defense of the area. Social activities within a group vary from almost 50% of daily activities to just a small percentage over the course of a year. The proportion of social activities increases when the fruits ripen. The three main types are grooming , playing (fighting, chasing, hitting, and biting) and other social contacts, the former being the most common. Aggression is rare. In principle, young white-handed gibbons play more than adults. There are some indications that body care with white-handed gibbons has mainly a hygienic and less a social function and is mostly mutual. The reactions to encounters with other groups range from agonism (physical confrontations) to friendly behavior (common grooming and playing together). Most interactions, however, are agonistic, but they can be purely vowel and even neutral (both groups hardly react to each other when they meet). Groups sometimes wander, eat or rest together when they come into contact. Males are the main participants in territorial disputes, but females are also sometimes involved. Conflicts usually occur near the boundaries of the district when two groups can see each other. They often last more than an hour and are accompanied by loud calls. The different types of interactions between neighboring groups are believed to be the result of different social and family relationships among their members. Even so, these arguments can be quite intense and there is evidence that wounds caused by territorial battles sometimes lead to the death of the animal. These clashes vary with the seasons and are more common when there are many fruits to defend. In a long-term study, males left their parents' territory at around 10 years of age and conquered their own territory by displacing a resident adult. Between your own territory and that of your parents there are usually one or two more, on average 1 km. The density of white-handed gibbons ranges from 2 groups per km ² in the Ketambe Research Station, in Gunung Leuser National Park on Sumatra to 3 groups per km ² and in Kuala Lompat and Tanjong Triang on the Malay Peninsula to 6 groups per km ² in the national park Khao Yai.

food

White-handed gibbons feed on a wide variety of foods. Figs and other small, sweet fruits are preferred, but young leaves, buds, flowers, young shoots, berries, vines, tendrils, insects (including praying mantises and wasps ), and bird eggs are also not spurned. They are known to eat parts of over 100 different types of plants. The menu changes within a year. In Khao Yai National Park, for example, fruits dominate all year round except in November and December. Flowers are most commonly eaten during these cool months, while ripe fruits are eaten in the hot and wet season. In the cool season, the menu is much more varied, as they then eat less fruit. However, fruits (including figs) never make up less than 50% of a year's diet. On average, the menu consists of 66% fruits, 24% leaves, 9% insects and 1% flowers.

White-handed gibbons compete with the sympatric, larger Siamang , whose presence often causes conflicts and makes it difficult for the white-handed gibbons to find food. The southern porcupine monkey ( Macaca nemestrina ) is also a food competitor , because both species have already been observed while searching for food together, as well as the long- tailed macaque ( M. fascicularis ) and the southern long-tailed langur ( Trachypithecus obscurus ).

Reproduction

White-handed gibbon cub

The white-handed gibbon has a menstrual cycle of 15-25 days (average 21-22 days). In the wild, females usually first reproduce at age 11 (ranging from 9 years and 9 months to 12 years and 9 months). The interval between births is at least three years. However, if a female loses a cub, ovulation may occur earlier. Females exhibit swelling, protrusion, and color change in the sexual skin region during ovulation, usually for about 7-11 days. In addition, swelling of the vulva (pubic area) occurs in pregnant females in the third month. Mating can occur any month, but most can be seen in the dry season (March). Sexual approaches by females involve placing oneself in front of a male and showing the genitals. Mating occurs dorso-ventrally (the male behind the female). Females refuse copulation by running away from the male, shouting loudly or rejecting his approach. Homosexual behavior has been demonstrated in male white-handed gibbons in the wild. Gestation lasts over six months in the wild. In one study area in Thailand, births fell in the late rainy and early dry seasons between September and October. Newborns weigh an average of 383 g and are almost naked except for a few hairs on their heads. You can call shortly after the birth. Parental care is mostly provided by the mother, but the father and older siblings also help her. In the wild, the baby clings as an active support Ling on the mother's abdomen and is so worn by her. Observations of young animals in the wild and in captivity show that solid food is consumed for the first time at four months. At this age, the young in the wild began to move away from the mother for a short distance, while the ability of the young animal in captivity was first demonstrated at nine months of age. Young animals are suckled until they are 28 months of age. The mortality of the young animals with less than 10% in the first year of life is low. Adolescents, regardless of gender, are fully grown at the age of six, but remain in their parents' territory until they have reached sexual maturity at the age of 8–9. The generation length is 15 years. In regions where there are many white-handed gibbons, however, sexual maturity does not occur until later, around 8–10 years (females) or 8–12 years (males). White-handed gibbons live to be at least 40 years old in the wild, but up to 50 years old in captivity.

hybrid

In North American and European zoos, hybrids (crosses) between the different gibbon species were quite common in the 1980s . So are hybrids between the white-hand gibbon and the western white-browed gibbon ( Hoolock hoolock ), the silver gibbon ( H. moloch ), the gray gibbon ( H. muelleri ), the cap gibbon ( H. pileatus ), the northern white-cheeked gibbon ( Nomascus leucogenys ) and the black-hand gibbon ( H. agilis ) known.

Hybrids are also regularly found in the wild. On the upper reaches of the Mudah River in the northwest of the Malay Peninsula, the white-hand gibbon hybridizes with the black-hand gibbon. However, human activities (deforestation and the creation of an artificial lake) have almost completely destroyed this hybrid zone, so hybridizations are now less frequent.

Hybridizations with the cap gibbon occur on the upper reaches of the Takhong River in Thailand over 120 km northeast of Bangkok in the Khao Yai National Park. The hybrids are viable and capable of reproduction and were or are still relatively common in zoos (e.g. in the Opel Zoo in Hesse ). The coat is light after birth and darkens with age. Among 61 gibbon groups in the hybrid zone, at least 18 were hybrids. However, backcrosses are not that easy to spot. The index of morphological features shifts over a distance of nine kilometers from 90% white-hand gibbon to 90% cap gibbon. But here, too, human interventions in nature have reduced the contact zone between the two species. South of the national park are rice fields that extend to the Gulf of Thailand . There was probably a wide area of ​​interspecific contact in the upper reaches of the river. It is believed that this hybrid zone was originally over 120 km long. Thomas Geissmann , who examined the chants of the hybrids, found that the characteristics that characterize the chants usually also occur in other gibbon species (not necessarily in the parental species). It is solely the combination of these traits that seems new to the hybrid's song. The characteristics of the song show influences from both the cap gibbon and the white-handed gibbon and some characteristics are intermediate between those of the parent species. In certain characteristics, the song of male hybrids resembles that of the black-handed gibbon. It has three-part elements that can neither be found in the singing of the parents, nor can their singing characteristics have arisen through a simple combination. The reputation of the female hybrid is remarkably similar to that of the silver gibbon.

Systematics

The white-handed gibbon was described by Linnaeus in his work Systema Naturae in 1771 as Homo lar . The type locality was determined by C. Kloss in Malaysia, Malacca , in 1929 .

Linnaeus described the species as follows:

"Hips bare; Arms as long as the trunk. Long-arm monkey. Found in India; meek, indolent, does not like rain or cold; 120 cm high. Face flesh-colored, naked, surrounded by a circle of gray hair; Eyes big; Color ranges from black to white; more upright than S. satyrus . [...] "

- Linnaeus : translated by William Turton (1806)

For decades the systematics of gibbons was confusing and disordered, so that some species were given more than one species name, which are no longer valid because they are synonymous. So it was with the white-handed gibbon:

• Simia albimana Vigors & Horsfield, 1828
• Hylobates longimana Schreber, 1774
• Pithecus variegates É. Geoffroy, 1812
• Hylobates varius Latreille, 1801

The external system of gibbons is highly controversial and has changed a lot over the years. Usually the white-handed gibbon is seen as a close relative of the black-handed gibbon ( H. agilis ) and its sister species, the white-bearded gibbon ( H. albibarbis ). Together with the Silvery ( H. moloch ), the Gray Gibbon ( H. muelleri ) and sometimes with the pileated ( H. pileatus ), it forms the lar group which the Mentawai Gibbon ( H. Defiant is compared with). Like all other species of the genus Hylobates , the white-handed gibbon has 44 chromosomes .

The various subspecies are not very divergent and differ only relatively weakly in terms of coat color and the degree of color polymorphism. The validity (validity) of H. l. yunnanensis as a separate subspecies is doubtful and probably synonymous with H. l. carpenteri . Some authors see H. l. yunnanensis as a subspecies in its own right, but this is due to the fact that the population is probably extinct.

The white-handed gibbon developed about 500,000 years ago in the Middle Pleistocene on the Malay Peninsula and then spread north to Thailand and north of Sumatra north of Lake Toba. The spread to the island was made possible by the drying up of the Sunda Shelf , which partly dried out as a result of the Ice Age , which bound large amounts of water in ice, thus making migrations between the mainland and the individual islands possible.

White-handed gibbons and people

etymology

The name "white-hand gibbon" refers to the white hands.

threat

White-handed gibbon in Kaeng Krachan National Park , Phetchaburi , Thailand

In China, there were an estimated 200 individuals on both sides of the Nangunhe River during the 1960s. In 1988 the white-handed gibbon was last sighted here and it has been estimated that fewer than 10 groups still exist. There has been no direct evidence of the species in this region since 1992. It is assumed, however, that three groups with about 10 individuals still exist. How many specimens are found in Myanmar, Indonesia and Malaysia is not known, while there are no reliable figures for Laos. Here they are only known from the Nam Phouy National Biodiversity Protected Area and are considered to be infrequent to rare (several hundred individuals). Several groups exist in some areas of Thailand with a total membership of at least 1,000, although they are now rare in northern Thailand. The largest population lives in the Kaeng Krachan National Park with sizes of 3000 to 4000 individuals. The Western Forest Complex , which includes several protected areas, is home to a total of 10,000 animals and 1,000 specimens are found in the Phukhieo Wildlife Sanctuary , in the Nam Nao National Park and in the west of the Khao Yai National Park . A few smaller populations live further south e.g. B. in the national park Khao Sok .

The greatest threat to the white-handed gibbon is hunting (it has even pushed forest clearing from the top spot). They are hunted for consumption and the pet trade. Hunting varies in strength depending on the region and is even practiced in nature reserves. Much of the hunt is done by villagers who cut down agarwood trees ( Aquilaria ) for their valuable, aromatic wood. Road construction (for example the highway through the Nam Phouy National Biodiversity Protected Area and the North-South Expressway in Malaysia) also pose a threat, as it necessitates deforestation and, due to the fragmentation of forests, gives hunters better access. Progressive habitat loss is also exacerbated by agriculture and oil palm plantations. Most of the lowland forests in northern Sumatra have been cleared and the plan for a road network called “Ladia Galaska” to connect the east and west coasts of Aceh province means that much of the remaining forests are also in danger.

The white-handed gibbon is classified as "endangered" by the International Union for Conservation of Nature and Natural Resources (IUCN). Like all gibbon species, it is protected in all countries in its range and listed in Appendix I of the Washington Convention on the Protection of Species . Almost everywhere it is restricted to protected areas (as in Thailand, where no significant populations can be found outside the protected areas). But in most countries these protected areas are not well monitored, even if they are maintained for tourism. There is an urgent need for improved protection of these areas, ideally with the involvement of the local population. Illegal use of forest products and poaching is common in most protected areas. Inadequate management and protection, not forest degradation, are the most important long-term threats. Further population counts are necessary in order to obtain up-to-date information on the populations in the protected areas. One such focus area is in southwest Yunnan, where it is unclear whether the species even survived here.

literature

• Ronald M. Nowak: Mammals of the World. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9 .
• Thomas Geissmann : Comparative Primatology. Springer, Berlin 2003, ISBN 3-540-43645-6 .
• Russell A. Mittermeier, Anthony B. Rylands, Don E. Wilson: Handbook of the Mammals of the World. Volume 3: Primates. Lynx Edition, Barcelona 2013, ISBN 978-84-96553-89-7 , pp. 781-783.

Web links

Commons : White-handed gibbon ( Hylobates lar )  - Collection of images, videos and audio files

Wiktionary: White-handed gibbon  - explanations of meanings, word origins, synonyms, translations

• Information from the Gibbon Research Lab. (English), with photos
• Scientific rehabilitation project for white-hand gibbons raised in captivity in Thailand (English)
• Hylobates lar in the endangered Red List species the IUCN 2006. Posted by: Eudey et al, 2000. Retrieved on 11 May 2006..

Individual evidence

1. ↑ Claudia Barelli, Christophe Boesch, Michael Heistermann, Ulrich H. Reichard: Female white-handed gibbons (Hylobates lar) lead group movements and have priority of access to food resources. ( Memento of March 4, 2016 in the Internet Archive ) (PDF) In: Behavior 154, 2008, pp. 965–981.
2. ↑ Claudia Whitington, Uthai Treesucon: Selection and treatment of food plants by white-handed Gibbons (Hylobates lar) in Khao Yai National Park, Thailand ( Memento from July 28, 2014 in the Internet Archive ) (PDF) In: Nat. Hist. Bull. Siam Soc. 39, 1991, pp. 111-122.
3. ↑ Bagemihl 1999, pp. 288-290.
4. ↑ International Zoo Yearbook 1974, p. 373.
   - International Zoo Yearbook 1977, p. 307.
5. ↑ International Zoo Yearbook 1967, p. 306.
   - International Zoo Yearbook 1968, p. 295.
   - International Zoo Yearbook 1973, p. 325.
   - International Zoo Yearbook 1977, p. 307.
   - International Zoo Yearbook 1986, p. 480.
   - International Zoo Yearbook 1989, p. 320.
6. ↑ Geissmann 1984.
   - Geissmann 1993.
   - Geissmann 2000.
   - Tenaza 1985.
7. ↑ Brockelman 1978.
   - Brockelman & Gittins 1984.
   - Brockelman & Schilling 1984.
   - Brockelman & Srikosamatara 1984.
   - Geissmann 1984.
   - Geissmann 1991.
   - Geissmann 1993.
   - Ibscher 1964.
   - Ibscher 1967.
   - International Zoo Yearbook 1961.
   - International Zoo Yearbook 1962.
   - International Zoo Yearbook 1963.
   - International Zoo Yearbook 1966.
   - International Zoo Yearbook 1968.
   - International Zoo Yearbook 1969.
   - International Zoo Yearbook 1970.
   - International Zoo Yearbook 1971.
   - International Zoo Yearbook 1972.
   - International Zoo Yearbook 1974.
   - International Zoo Yearbook 1979.
   - International Zoo Yearbook 1980.
   - International Zoo Yearbook 1982.
   - International Zoo Yearbook 1990.
   - Marshall & Brockelman 1986.
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   - Meyer-Holzapfel 1950a.
   - Steiner 1949.
   - Suwanvecho & Brockelman 2012.
8. ↑ S. Baicharoen, T. Miyabe-Nishiwaki, Y. Hirai, K. Duangsa-ard, B. Siriaroonrat, H. Hirai: Intergeneric and interspecific hybrids in Gibbons: Chromosomal aspects of the small ape evolution. Abstract (PDF), International Primatology Society, XXII Congress Kyoto 2010, p. 442.
9. ↑ Brockelman & Gittins 1984.
   - Gittins 1978.
   - Gittins 1984.
   - Groves 1993.
   - Chiarelli 1961.
   - International Zoo Yearbook 1966, p. 391.
   - International Zoo Yearbook 1972, p. 320.
   - Steiner 1949.
10. ↑ INTERGENERIC AND INTERSPECIFIC HYBRIDS IN GIBBONS: CHROMOSOMAL ASPECTS OF THE SMALL APE EVOLUTION. In: jstage.jst.go.jp. March 4, 2011, accessed December 12, 2019 . 
11. ↑ [1]
12. ^ Russell A. Mittermeier, Anthony B. Rylands, Don E. Wilson: Handbook of the Mammals of the World. Volume 3: Primates. Lynx Edition, Barcelona 2013, ISBN 978-84-96553-89-7 , p. 755.
13. ^ Russell A. Mittermeier, Anthony B. Rylands, Don E. Wilson: Handbook of the Mammals of the World. Volume 3: Primates. Lynx Edition, Barcelona 2013, ISBN 978-84-96553-89-7 , p. 754.