Hoolock leuconedys
Creators: name: Russell A. Mittermeier
name: Anthony B. Rylands
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Primates
Hylobatidae
Hoolock
Hoolock leuconedys

description: 2.
Eastern Hoolock Gibbon
Hoolock leuconedys
French: Gibbon de Groves / German: Ostlicher WeiRbrauengibbon / Spanish: Gibén huloc oriental
Taxonomy. Hylobates hoolock leuconedys Groves, 1967,
Burma (= Myanmar), Sumprabum, 1200 m.
Previously considered a subspecies of H. hoolock, but now treated as a full species. It is separated from H. hoolock by the Chindwin River, although intermediates may occur in the headwaters. Monotypic.
Distribution. NE India, marginally in the states of Arunachal Pradesh (Lohit and Lower Dibang Valley districts) and Assam (Tinsukia District), E Myanmar (E of the Chindwin River), and S China in W Yunnan Province.
Descriptive notes. Head-body 45-65 cm; weight 6-9 kg. In a mixed sex sample from China, the average weight was 7-2 kg (n = 5). The Eastern Hoolock Gibbon is distinguished from the Western Hoolock Gibbon (H. hoolock) by its white preputial tuft, the complete separation of the white eyebrows, a lighter silvery chest, and generally white hairs under the eyes and on the chin in the black phase. Hands of females may be lighter in color than the body.
Habitat. Closed-canopy, lowland, broadleaved evergreen forest; lowland, semi-evergreen, and mixed deciduous forests and higher elevation evergreen and semi-evergreen forests. Elevational records of the Eastern Hoolock Gibbon are 1600-2600 m in China, 142-1865 m in India, and up to ¢.2300 m in Myanmar.
Food and Feeding. There is no specific information for this species, but its diet and feeding behavior are probably similar to those of the Western Hoolock Gibbon.
Breeding. First menstruation occurred in one female Eastern Hoolock Gibbon at about seven years of age.
Activity patterns. The Eastern Hoolock Gibbon is diurnal and arboreal. No behavioral studies have been published on Eastern Hoolock Gibbons, but they are probably similar in their behavior to Western Hoolock Gibbons. In India, Eastern Hoolock Gibbons call between 07:00 h and 12:00 h, and singing bouts last 5-35 minutes and average 18 minutes.
Movements, Home range and Social organization. The Eastern Hoolock Gibbon is presumably territorial, although no specific data exist. Mean group size has been recorded in a number of population surveys; 3-9 individuals (n = 9) in China, three individuals (n = 7) in Mahamyaing Wildlife Sanctuary, and 3-1 individuals (n = 28) in Mehao Wildlife Sanctuary, India. Two of nine groups observed in China had more than one adult female. Population density estimates from 17 spot surveys in Myanmar averaged 2-6 groups/km?. Densities from one well-studied site in Mahamyaing Wildlife Sanctuary, Myanmar, were 0-71-5-1 groups/km?in eleven sampled areas and averaged 2:2 groups/km?* or 8-9 ind/km®. At the time of this survey, densities seemed to be unaffected by recent selective logging at this site.
Status and Conservation. CITES Appendix I. Classified as Vulnerable on The IUCN Red List. The Eastern Hoolock Gibbon is legally protected in Myanmar, China, and India. Threats to the Myanmar population include hunting, especially in northern areas near the Chinese border, and habitat degradation and fragmentation. Some sites that maintain populations of Eastern Hoolock Gibbons apparently have no major threats. Since 1984, 56 locality records have been verified in Myanmar. Less than 200 individuals are now believed to persist in China, restricted to only three counties and fragmented into 17 subpopulations, the largest of which has only five groups. The population in Gaoligongshan National Nature Reserve, China, appears to be relatively secure, although it is small and therefore vulnerable. The Chinese population is declining, with nine recorded local extinctions in the past two decades and five subpopulations now having only one remaining group, suggesting their imminent demise. Local extinctions have been caused by logging operations, hunting, agricultural encroachment for cardamom cultivation, and shifting agriculture. Hunting of Eastern Hoolock Gibbons was very high in the past, but in some areas, local communities do not hunt them (although they do hunt other primates), which is at least partially responsible for their persistence. The population of Eastern Hoolock Gibbons in India is restricted to a small area in the north-east, with an estimated 3000 individuals, including c.157 groups in Mehao Wildlife Sanctuary. Populations in India are probably declining, with habitat destruction and hunting being the major threats. Habitat conversion for cultivation (including cardamom), habitat fragmentation, and slash-and-burn agriculture are threats in Mehao. The most significant populations occur in Myanmar, with a recent national status review suggesting a population of 290,000-370,000 individuals, based on density estimates from 17 spot surveys and an estimate of 42,500 km? of remaining habitat suitable for Eastern Hoolock Gibbons. Nevertheless, these estimates may have significant bias, because the areas surveyed were in localities known to have gibbons, sample size was small, and estimates of forest cover were problematic. Regardless, it is clear that Myanmar holds the vast majority of Eastern Hoolock Gibbons, with the Kachin Northern Forest Complex and Southern Kachin-Northern Sagaing forests estimated to hold the majority of the national and therefore global population. The best-documented population is in Mahamyaing Wildlife Sanctuary, which had an estimated 1051-2468 groups or 3500-8100 individuals in 2004. Overall, the Eastern Hoolock Gibbon occurs in at least eight protected areas including Gaoligongshan National Nature Reserve in China; Mehao and Kamlang wildlife sanctuaries in India; and Mahamyaing, Phongun Razi, Htamanthi, and Indawgyi Lake wildlife sanctuaries, and Panlaung-Padah-Lin Caves Reserved Forest in Myanmar. Additional populations in the headwaters on the Chindwin River including Hukawng Valley Wildlife Sanctuary and Hukawng Valley Tiger Reserve (an extension), Myanmar, are of unknown taxonomic affinity, existing in the transition zone between Eastern and Western hoolock gibbons.
Bibliography. Brockelman et al. (2009), Chetry & Chetry (2010, 2011), Chetry, Chetry, Das et al. (2008), Chetry, Chetry, Gosh & Singh (2010), Chivers (2001), Das, J. et al. (2006, 2009), Fan Pengfei & Ai Huaisen (2011), Fan Pengfei, Xiao Wen et al. (2011), Francis (2008), Geissmann (2007a), Groves (1967), Haimoff et al. (1987), Ji Weizhi & Jiang Xuelong (2004), Matthews (1946), Mootnick & Groves (2005), Ma Shilai et al. (1988), Ngwe Lwin et al. (2011), Smith & Jungers (1997), Van Ngoc Thinh, Mootnick, Geissmann et al. (2010), Yang Dehua et al. (1987), Zhang Yongzu et al. (2002).
description: Published as part of Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Hylobatidae, pp. 778-791 in Handbook of the Mammals of the World – Volume 3 Primates, Barcelona :Lynx Edicions on pages 779-780, DOI: 10.5281/zenodo.6727957