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Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hylobatidae — gibbons
Genus: Nomascus
Species: Nomascus gabriellae — red-cheeked gibbon; see synonyms, below
Source: ITIS (2018)
Synonyms
- Hylobates gabriellae (Geissmann 2008)
- Southern yellow-cheeked (crested) gibbon (ITIS 2018)
- Yellow-cheeked crested gibbon (Traeholt et al. 2005)
- Buff-cheeked gibbon (ITIS 2018)
- Golden-cheeked gibbon (Varsik and Santa Barbara Zoological Gardens 2001)
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Body Weight
- Adult: 5-12 kg (11-26 lb) (Sheeran and Mootnick 1998; Bartlett 2011; Bạch Thanh Hải, personal communication, 2018)
- Infant: 0.5-1 kg (1-2 lb) (Bạch Thanh Hải, personal communication, 2018)
Head-body Length
- Male: 45.5-49.6 cm (17.9-19.5 in) (Chivers et al. 2013)
- Female: 46-47.5 cm (18-18.7 in) (Chivers et al. 2013)
Pelage (Traeholt et al. 2005; Chivers et al. 2013; also see Mootnick and Fan 2011)
- Males and females have different color hair, like other Nomascus species.
- Adult male black, except for yellow/orange cheeks and slightly rusty-colored chest. Adult female pale yellow to orange-yellow. May have black crown. May have slightly darker chest.
- Infants born buff-yellow. Begin to transition to black coloration (same as adult males) at about six months old. Retain this coloration as juveniles and subadults. As adults, males retain black coloration. Females transition back to yellow upon reaching maturity.
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Range
Southern Vietnam and eastern Cambodia. After taxonomic split with N. annamensis, no longer thought to inhabit Laos (Rawson et al. 2011; Thien et al. 2017).
Habitat
Wet evergreen and semi-evergreen forests. Mixed deciduous forest (especially where mixed with patches of evergreen forest), bamboo forests, and rattan (Old World palms) (Traeholt et al. 2005; Rawson et al. 2009; Chivers et al. 2013).
IUCN Status
Endangered (2015 assessment) (Rawson et al. 2020)
CITES Appendix
Appendix I (UNEP 2020)
Other Designations
Legally protected in Vietnam and Cambodia (Chivers et al. 2013).
Populations in the Wild
Population trend: decreasing (Geissmann et al. 2008; Rawson et al. 2011). Highest densities in undisturbed forests (Chivers et al. 2013; Vu et al. 2016).
Few robust population estimates:
- Cambodia (estimates missing from some regions): 450-1,350 groups (Chivers et al. 2013).
- Vietnam: Approximately 600 groups (see references in Bach et al. 2017), plus groups from non-surveyed areas; considered “common” (Traeholt et al. 2005). Cat Tien and Bu Gia Map National Parks support the largest N. gabriellae populations in Vietnam (Rawson et al. 2011).
Threats to Survival
- Hunting for wildlife trade. Mothers shot and infants traded for pet trade (e.g., Rawson et al. 2011).
- Also hunted for food (Geissmann et al. 2008; Rawson et al. 2011; Chivers et al. 2013) and traditional medicine (Rawson et al. 2009).
- Habitat loss: infrastructure development, agriculture, illegal logging (Rawson et al. 2009)
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Activity Cycle
Diurnal—active early morning until late afternoon (Chivers et al. 2013).
Movements (Kenyon et al. 2011; Chivers et al. 2013)
After reaching sexual maturity, females disperse from natal territories to nearby territories. Males may disperse farther, if no space available in nearby territories.
Social Behavior
Territorial (Rawson et al. 2011). Family unit comprised of adult pair and offspring. Usually 4-5 individuals (range: 3-6) in a group (Kenyon et al. 2011); however, larger multi-female groups have been observed (Barca et al. 2016).
Communication
Often loud calls around sunrise (Rawson 2004; Rawson et al. 2009). Adult male and female usually sing in duet (Geissmann 2002). Singing bouts about 12 minutes long (Rawson 2004). Immatures do not usually duet but occasionally call with group (Bartlett 2011).
Diet
Mainly figs and other fruits; flowers, leaves, and shoots (Chivers et al. 2013; Bach et al. 2017).
Also insects and bird eggs (Bach et al. 2017).
Predators
Not well known. Pythons, leopards, birds of prey (eagles), large macaques (Bạch Thanh Hải, personal communication, 2018).
Locomotion
Arboreal. Swing among tree branches from hand to hand (“brachiation”), climb, run on two feet, leap (Fleagle 1976).
Relationship with Humans
Shy around humans (Traeholt et al. 2005). Cryptic—difficult to observe in the wild (Barca et al. 2016). In southern Vietnam, held as pets in hotels and private zoos. Also hunted—see Threats to Survival (Rawson et al. 2011).
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Breeding
Monogamous. Uncommonly, extra-pair copulations (Kenyon et al. 2011) and multi-female groups (Barca et al. 2016).
Sexual Maturity
Not well known for Nomascus (Rawson et al. 2011).
Among gibbons, generally, mature as early as 5 years in managed care and likely at 7-8 years in the wild (Geissmann 1991).
Ovarian Cycle
About 21 days [data from 7 cycles of 2 females], similar to other gibbons (Geissmann and Anzenberger 2009).
Gestation
Not known. Likely similar to N. leucogenys, 200-212 days (about 7 months) (Geissmann 1991).
Litter Size
One young (Rawson et al. 2011)
Interbirth Interval
One observation in N. gabriellae of 17-22 months (Chivers et al. 2013). Approximately 2-4 years in some other gibbons (Traeholt et al. 2005; see references in Bartlett 2011).
Age at Weaning
Generally, gibbons weaned during second year (Bartlett 2011).
Typical Life Expectancy
Wild populations: not known
Managed care: no AZA estimates
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Feature Facts
- Very long arms for swinging and climbing in trees (Cheyne 2011)
- Stable pair bonds (Bartlett 2011)
- Gibbon songs may strengthen bonds between mates and advertise territory holdings (Bartlett 2011)
- Female and male sing different songs (Rawson 2004)
- Compete with other animals (e.g., macaques, squirrels) for ripe fruits (Hai et al. 2018)
- Important disperser of seeds for the tropical rainforest canopy tree, the Pacific walnut (Dracontomelon dao) (Hai et al. 2018)
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