Hylobates funereus, Geoffroy Saint-Hilaire, 1850
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https://doi.org/ 10.5281/zenodo.6727957 |
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DOI |
https://doi.org/10.5281/zenodo.6728299 |
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persistent identifier |
https://treatment.plazi.org/id/03D787BA-0E3F-FFC7-FA3A-F531FEA8C1BB |
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treatment provided by |
Jonas |
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Hylobates funereus |
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10. View Plate 53: Hylobatidae
East Bornean Gray Gibbon
Hylobates funereus View in CoL
French: Gibbon de Geoffroy / German: Ostlicher Borneo-Gibbon / Spanish: Gibén de Sabah
Other common names: Eastern Miller's Gibbon
Taxonomy. Hylobates funereus 1. Geoffroy Saint-Hilaire, 1850 View in CoL ,
Philippines, Sulu Islands.
The type locality is obviously in error, which may have arisen because Sabah was formerly part of the Sultanate of Sulu. Until recently, H. funereus was considered a subspecies of H. mueller, but morphologically and genetically it is a distinct species. There are wide intergrade zones between H. funereus , H. muelleri , and H. abbotti where their ranges meet. Monotypic.
Distribution. N & NE Borneo, from Sabah State S to the Mahakam River in East Kalimantan Province and perhaps W to the Baram District and the IV Division of Sarawak State. View Figure
Descriptive notes. Head—body 48-5 cm (males, n = 3) and 47.5-49 cm (females, n = 3); weight 5.6-4 kg. Pelage of the East Bornean Gray Gibbon is very dark brown or gray. Hands and feet are not darker than limbs and are sometimes lighter. The crown hair is directed fanwise from the front of the scalp and is markedly elongated over the ears.
Habitat. Primary and secondary semi-deciduous monsoon, dipterocarp, and tropical evergreen forest. They are found to about 1700 m above sea level in Sabah, but densities decrease at higher elevations. East Bornean Gray Gibbons have been studied by D. Leighton in Kutai National Park, East Kalimantan, north of the Mahakam River. The forest there is largely lowland dipterocarp (much ofit logged) but also includes tropical moist heath forest (“keranga”) on sandy acidic soils and, in the coastal area, mangroves. These gibbons can tolerate a degree of selective logging provided that sufficient tall, fruit-bearing trees are left standing.
Food and Feeding. The composition of the diet recorded over a year at Kutai was as follows: fruit 62% (monthly variation 27-90%); leaves 32% (8-73%); flowers 4% (0-6%); and insects 2% (0-6%). As for all gibbons,figs ( Ficus , Moraceae ) are important, averaging 24% ofthe fruit part of the diet.
Breeding. Breeding is not seasonal. Generally it is the male that initiates mating. Parental care is given predominantly by the mother, although the father and elder siblings assist, and the male spends more time than the female playing with and grooming the young. Juveniles of both sexes reach adult size at around six years old, but remain with their natal group until they reach sexual maturity at around 8-9 years. The birth interval is 36 months. Individuals can live up to 47 years.
Activity patterns. East Bornean Gray Gibbons travel and forage in the upper middle and upper canopy, 25-30 m above the ground. They sleep, rest, and sing in the canopies of emergent trees. They are active for 8-10 hours per day, usually starting at dawn but resting and retiring in the mid- to late afternoon well before sunset. Singing and feeding are most intense in the morning hours.
Movements, Home range and Social organization. At Kutai, seven family groups of East Bornean Gray Gibbons averaged 3-4 individuals; an adult male, adult female, and their offspring. The average home range size of four groups was found to be 36 ha (range 33-43 ha). The day range of the groups at Kutai averaged 800 m (350-1890 m). They use the ranges unevenly, but will generally visit all parts of it over a few days. They do not habitually patrol the range, but the simulation of an intrusion using playback does result in some monitoring of the range borders. Females initiate duets and lead joint approaches to playbacks of female solos, whereas males lead silent, joint approaches to playbacks of male solos. In general, males are aggressive toward other males and defend their territory, while females lead the group’s daily progressions and are aggressive toward other females. Females tend to be more aggressive than males, and are dominant over them. The female grooms the male much less frequently than vice versa. The male is the more aggressive during intergroup encounters. Densities, estimated using various techniques, range from 9-14-6 ind/km? at Kutai National Park to 6-9-9-9 ind/km* at Kayang Mentarang National Park.
Status and Conservation. CITES Appendix I. Classified as Endangered on The IUCN Red List (as H. mueller: funereus ). The East Bornean Gray Gibbon is protected under Indonesian and Malaysian law. It is generally common where good forest remains, although logging activities have rendered the range patchy. The widespread fires in the El Nino years in the 1980s and 1990s devastated forests over a large part ofits range. Much of its habitat was also lost in colonial times and is being further impacted by oil palm plantations and logging activities. Deforestation, trade in illegal pets, and hunting are the predominant threats. East Bornean Gray Gibbons occur in the following protected areas: Kutai and Kayan Mentarang national parks in East Kalimantan (Indonesia); Tawau Hills, Kinabalu, and Crocker Range national parks in Sabah (Malaysia); Pulong Tau, Gunung Mulu, and Gunug Buda national parks in Sarawak (Malaysia); and Ulu Temburong National Park in Brunei. There is no population estimate for the East Bornean Gray Gibbon , but “gray gibbons” (Muller's, H. muelleri , East Bornean Gray, and Abbott's Gray, H. abbotti , gibbons) have been estimated at 250,000-375,000 individuals.
Bibliography. Bartlett (2007), Brody & Brody (1974), Chivers (2001), Geissmann & Nijman (2008c), Groves (2001), Haimoff (1985a), Haraway et al. (1988), Hirai, Hayano et al. (2009), Hirai, Wijayanto et al. (2005), Kloss (1929), Leighton (1987), Maples et al. (1988), Mather (1992), Meijaard et al. (2005), Mitani (1984, 1985a, 1985b), Nijman (2005), Nijman & Menken (2001), Oka & Takenaka (2001), Payne et al. (1985), Rodman (1978), Short (2004), Stott & Selsor (1961), Tenaza (1985), Van Ngoc Thinh, Mootnick, Geissmann et al. (2010), Yasuma & Andau (2000).
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