Gibbon

Etymology and Terminology

The English word gibbon is a loan from French, first recorded in the eighteenth century.^[7][8] Georges-Louis Leclerc, Comte de Buffon, used the term in 1766 in the fourteenth volume of his Histoire Naturelle.^[9][10] Buffon attributed the introduction of the term to Joseph Francois Dupleix, the French colonial administrator.^[11][12] Linguistic studies suggest that the term originally derives from an Orang Asli language of the Malay Peninsula, specifically from the nomadic Semang or Menraq communities speaking Northern Asli dialects, where the root term kbon or kbɔɲ referred to arboreal hylobatid apes.^[7][13][14]

The scientific family name Hylobatidae was established from the ancient Greek words hyle, meaning forest or woods, and bates, meaning walker or roamer, translating literally to forest wanderers.^[15] Colloquially and across academic literature, hylobatids are commonly referred to as lesser apes or small apes, setting them apart from the great apes of the family Hominidae, which comprises chimpanzees, bonobos, gorillas, orangutans, and humans.^[1][16][17] In local regions across Southeast Asia, vernacular names such as ungka, wau-wau, wak-wak, and owa are onomatopoeic renderings of their distinctive vocalizations.^[18][19][20]

Evolutionary History and Fossil Record

Gibbons form the basal sister clade to the family Hominidae within the superfamily Hominoidea.^[21][22] Their precise evolutionary origin has been challenging to establish due to an impoverished fossil record and mosaic anatomical features.^[23][24] Historically, fossil catarrhines from the Miocene and Oligocene of Africa and Eurasia, including Dendropithecus, Propliopithecus, Pliopithecus, Epipliopithecus, Micropithecus, and Dionysopithecus, were considered potential ancestors or relatives of gibbons.^{[23][25][26][27]} Although these extinct taxa shared slender limbs, brachiating tendencies, or dentition adapted to frugivory, they retained extremely primitive skeletal traits and had long tails.^[3][23] The fossil species Pliobates cataloniae, discovered in Spain and dating to 11.6 million years ago, was initially interpreted as a stem hominoid indicating that hominoid ancestors were gibbon-like, though later re-evaluations placed it as an advanced stem catarrhine unrelated to hylobatid divergence.^[28][29]

The most credible fossil candidates for early hylobatids have been unearthed in South and East Asia.^[23] The genus Kapi, represented by a fossil molar found in Ramnagar in Jammu and Kashmir, India, dates to 12 to 13 million years ago and represents the oldest identified candidate ancestor of modern gibbons.^[23][30][31] The genus Yuanmoupithecus, discovered in Yunnan, China, dates to the late Miocene around 7.1 to 9 million years ago and displays dental and cranial affinities with living hylobatids.^[23][32][33] Extinct Pleistocene fossils from southern China, including Bunopithecus sericus from Middle Pleistocene deposits in Sichuan, as well as fossilized remains of extant species like Nomascus concolor and Hoolock hoolock, demonstrate that hylobatids occupied a broader geographic range during the Pleistocene than in historical times.^[34][35]

Phylogeny and Divergence

Molecular dating analyses suggest that the gibbon lineage diverged from the ancestor of great apes during the early to middle Miocene.^[24][36] Adaptive radiation of the four extant genera occurred rapidly during the late Miocene to early Pliocene, approximately 5 to 7 million years ago.^[36][37] This radiative burst may have been driven by geological uplifts of continental plateaus, dynamic sea-level fluctuations across the Sunda Shelf, and cyclical expansions and contractions of tropical forest canopies.^[24][36][38] Because speciation occurred within a very narrow evolutionary window, phylogenetic reconstruction has been obscured by extensive incomplete lineage sorting, where genealogical gene trees conflict with species bifurcations.^[22][36][39]

Phylogenetic topologies for the four extant genera have differed depending on whether morphological, mitochondrial, or nuclear datasets were examined.^[37][40][41] An analysis based on morphology suggests that the four genera are ordered as (Symphalangus, (Nomascus, (Hoolock, Hylobates))).^[40] Conversely, comprehensive phylogenomic and coalescent-based analyses of whole-genome datasets support an initial divergence of Hylobates, followed by Nomascus, with Hoolock and Symphalangus forming sister clades: (Hylobates, (Nomascus, (Hoolock, Symphalangus))).^[42][43][44] Alternative mitochondrial and acoustic studies have proposed trees grouping Hoolock as basal, or placing Nomascus and Symphalangus together.^{[45][46][47][48]}

Within the genus Hylobates, species-level divergence has been resolved through mitogenomic and nuclear sequencing. Hylobates pileatus diverged first, separating from the common ancestor of Hylobates lar and Hylobates agilis around 3.9 million years ago, followed by the separation between H. lar and H. agilis approximately 3.3 million years ago.^[39][49] Whole-genome comparisons indicate that Hylobates pileatus split from Hylobates moloch between 1.5 and 3.0 million years ago.^[36] Speciations within Hylobates and Nomascus intensified during the Pleistocene between 2.8 and 1.5 million years ago, facilitated by periodic land bridges during marine regressions that allowed migration across Sundaland, followed by vicariant isolation and demographic bottlenecks.^[43][50][51]

Genomics and Chromosomal Evolution

The hylobatid genome shares approximately 96% sequence similarity with the human genome. Despite this close genetic proximity, gibbon karyotypes have undergone an unprecedented rate of rapid chromosomal rearrangement relative to the ancestral hominoid karyotype of 2n = 48.^[24][52] The common ancestor of hominoids requires a minimum of 24 major chromosomal rearrangements to match the ancestral gibbon karyotype, with up to 28 further rearrangements needed to yield modern gibbon forms, totaling at least 52 major chromosomal structural rearrangements.^[52] Segmental duplications host roughly 46% of all gibbon-human synteny breakpoints, indicating regions of concentrated genomic plasticity.^[52]

Whole-genome sequencing of a northern white-cheeked gibbon named Asia identified an active, gibbon-specific retrotransposon known as the LAVA element.^[36][53] This mobile jumping DNA element inserted into genomic positions between genes governing chromosome segregation and distribution during mitosis and cell division, causing premature transcription termination and triggering large-scale DNA inversions, deletions, and duplications.^[36][53] While some LAVA insertions disrupt normal transcription, other sequences appear to have been co-opted to assist DNA repair pathways.^[54] Genomic analyses have also highlighted signs of positive natural selection in genes governing skeletal and muscular adaptations, notably TBX5 for forelimb elongation, COL1A1 for reinforced collagen in bones and tendons, and chondrogenesis genes including CHAD duplications.^[36][53][55] A specific deletion discovered in the Sonic hedgehog (Shh) gene pathway was transferred into transgenic mice, producing significant experimental limb lengthening.^[43]

Hybrids

Because many gibbons are hard to identify by morphology and fur coloration, hybrids have arisen in many zoos; hybrids are also sometimes observed in the wild where species ranges overlap.^[56][57][58] In zoological facilities, gibbons of unknown geographic origins have historically been misidentified and co-housed, resulting in unintentional interspecific crosses.^[57][58] In the wild, natural hybrid zones occur between closely related parapatric species belonging to the same genus where their home ranges border one another, such as between Hylobates lar and Hylobates muelleri, or among Bornean grey gibbon forms.^[56][59][60] However, there are no verified records of fertile hybrids between different gibbon genera, either in the wild or in captivity.^[36][43][61]

Taxonomy and Classification

Formal taxonomic treatment of gibbons began in the eighteenth century. Carl Linnaeus described the lar gibbon in 1771 as Homo lar, placing it in the human genus.^[62][63] In 1811, Johann Karl Wilhelm Illiger erected the genus Hylobates to encompass all known gibbons.^[23][64] Early nineteenth-century naturalists often assigned gibbons to Simia or Pithecus.^[65][66] In 1870, John Edward Gray first set gibbons apart in a separate higher taxon, the tribe Hylobatina, while Edward Blyth recognized it formally as a standalone family in 1875.^[67][68][69] Throughout much of the nineteenth and twentieth centuries, alternative arrangements placed hylobatids as a subfamily, Hylobatinae, within the great ape family Pongidae, or even directly inside Cercopithecidae, Hominidae, or historical obsolete groupings such as Tylopyga, Anthropomorpha, and Cheiropoda.^{[16][25][70][71][72]}

For over a century, taxonomy grouped gibbons into either a single genus (Hylobates) or two genera (Hylobates and Symphalangus).^[16][37][73] During the late twentieth century, cytogenetic discoveries revealed four distinct diploid chromosome counts: Hoolock (2n = 38), Hylobates (2n = 44), Symphalangus (2n = 50), and Nomascus (2n = 52).^[74][75] Initially treated as subgenera within Hylobates, these lineages were elevated to four distinct extant genera during the 1980s through early 2000s, an arrangement reinforced by morphological, acoustic, and molecular lines of evidence.^[37][75][76] The hoolock gibbons, originally placed in the extinct genus Bunopithecus based on cranial similarities to Bunopithecus sericus, were established in their own genus Hoolock in 2005.^[74][77][78]

Species-level taxonomy has expanded dramatically since Colin Groves recognized six species in 1972, driven by genetic evaluations, bioacoustics, and the widespread adoption of the phylogenetic species concept over the biological species concept.^[23][79] Modern consensus, including the Mammal Diversity Database and specialized primate compendia, recognizes four extant genera containing 20 extant species, alongside three extinct genera: Bunopithecus, Junzi, and Yuanmoupithecus.^{[23][80][81][82]} Junzi imperialis, identified in 2018 from a partial cranium in the royal tomb of Lady Xia, the grandmother of China's first emperor Qin Shi Huang, represents the first known hominoid extinction occurring after the Last Glacial Maximum, though some recent mitogenomic analyses place it within the genus Nomascus.^[43][83][84]

List of Genera and Species

The family Hylobatidae is divided into the following genera and recognized species: Genus Hoolock: * Western hoolock gibbon, Hoolock hoolock * Eastern hoolock gibbon, Hoolock leuconedys * Skywalker hoolock gibbon, Hoolock tianxing Genus Hylobates (dwarf gibbons): * Lar gibbon or white-handed gibbon, Hylobates lar * Bornean white-bearded gibbon, Hylobates albibarbis * Agile gibbon or black-handed gibbon, Hylobates agilis * Western grey gibbon or Abbott's grey gibbon, Hylobates abbotti * Eastern grey gibbon or northern grey gibbon, Hylobates funereus * Müller's gibbon or southern grey gibbon, Hylobates muelleri * Silvery gibbon, Hylobates moloch * Pileated gibbon, Hylobates pileatus * Kloss's gibbon or bilou, Hylobates klossii Genus Symphalangus: * Siamang, Symphalangus syndactylus Genus Nomascus (crested gibbons): * Northern buffed-cheeked gibbon, Nomascus annamensis * Western black crested gibbon, Nomascus concolor * Eastern black crested gibbon or Cao Vit gibbon, Nomascus nasutus * Hainan black crested gibbon, Nomascus hainanus * Northern white-cheeked gibbon, Nomascus leucogenys * Southern white-cheeked gibbon, Nomascus siki * Yellow-cheeked gibbon, Nomascus gabriellae Extinct fossil genera: * Genus Bunopithecus, including Bunopithecus sericus * Genus Junzi, including Junzi imperialis (alternatively classified as Nomascus imperialis) * Genus Yuanmoupithecus, including Yuanmoupithecus xiaoyuan * Genus Kapi, including Kapi ramnagarensis.^{[23][31][43][80][85][86][87]}

Physical Description and Anatomy

Hylobatids are the smallest hominoids, typically matching macaques in general body size.^[23][88] Head-and-body length ranges from 44 to 90 cm across the family.^[89] The largest species is the siamang, weighing 10.7 to 11.9 kg (occasionally reaching 13 to 14 kg) with an arm span of up to 1.5 m, exceeding other gibbons by 1.5 to 2 times.^[89][90][91] Species in the genus Hylobates are the smallest, weighing 4 to 8 kg (averaging 5.3 to 5.9 kg), with Kloss's gibbon and female lar gibbons exhibiting the lowest weights, around 4 kg.^[90][92][93] Gibbons of the genus Hoolock average around 6.9 kg, while Nomascus species average 7.3 to 7.8 kg.^[90] Body size sexual dimorphism is largely absent across all species, with males and females exhibiting comparable weights and dimensions, except for minor cranial and corporal dimorphism in siamangs.^[1][88]

Gibbon limb anatomy exhibits specializations for locomotion.^[88] The upper limbs are extraordinarily elongated, exceeding double the length of the torso, while the lower limbs are nearly 1.5 times torso length.^[94][95] The scapula is narrow and elongated, featuring a shallow, reduced glenoid cavity that grants an exceptional range of motion at the cost of skeletal joint stability.^[96] The humeral head is larger than the femoral head, reflecting reliance on arm suspension.^[97] The wrist possesses an internal ball-and-socket joint that permits smooth biaxial rotation, markedly reducing muscular effort in the shoulders and torso during swinging.^[98] The hand has elongated, hook-shaped fingers (digits II through V), while the opposable thumb is set deeply back toward the wrist by a cleft that penetrates into the metacarpus.^[3][98][99] In the siamang, syndactyly joins the second and third digits of the foot with skin webbing, giving rise to its species name syndactylus.^[100]

Like all hominoids, gibbons are tailless.^[1][4] Unlike great apes, however, they retain prominent ischial callosities on their pelvic bones, a primitive trait shared with cercopithecid monkeys that provides unyielding support while perching on sturdy branches without nests.^[88][101] The vertebral column contains 18 combined thoracic and lumbar vertebrae above a flattened, widened thorax.^[4][92] Cranially, gibbons have a rounded, globular braincase, a short, flat face, and large, widely spaced orbits with projecting rims.^[23][88] The sagittal crest is generally absent.^[88] Their catarrhine nostrils are closely positioned and directed downward.^[95]

Dentition and Neurology

The hylobatid dental formula is 2.1.2.3 / 2.1.2.3, totaling 32 teeth.^[95] The molars are bunodont with low, rounded cusps; lower molars possess five cusps, while upper molars feature four cusps with an oblique crest connecting the protocone and metacone.^[88] Canines are dagger-shaped, elongated, and present in both sexes with minimal sexual dimorphism.^[88][102] The lower first premolar is sectorial and mediolingually elongated, forming a specialized honing and shearing mechanism when occluding against the posterior edge of the upper canine, a functional arrangement resembling Old World monkeys.^[88][102]

Neurologically, gibbons display a mosaic of hominoid and cercopithecoid neuroanatomical attributes.^[103] The absolute brain volume is modest, averaging roughly 83 cm3 in Hylobates lar, yet when scaled allometrically against body mass, brain size aligns with hominoids rather than monkeys.^[103] The relative neocortex ratio in the lar gibbon reaches 1.16, exceeding that measured in orangutans (1.14), gorillas (1.00), and chimpanzees (1.03).^[103] However, the gibbon cortex has fewer convolutions, with a gyrification index of only 1.9, noticeably below orangutans (2.29), gorillas (2.07), chimpanzees (2.19), and humans (2.57).^[103] The frontal lobe constitutes 29.4% of hemisphere volume in H. lar, matching proportions seen in capuchins and macaques and remaining below the 30% threshold standard in great apes.^[103]

Pelage, Coloration, and Throat Sacs

Gibbon pelage can be dense, or coarser and sparser, as in the siamang.^[3][4][104] Fur color varies widely across species from black and grey to various shades of brown, fawn, and cream.^[4] Face rings, white brow bands, pale cheek patches, or white extremities on the hands and feet are common.^[98][104] Species in the genus Nomascus possess distinctive crests of upright hair on the crown, accompanied by buff, white, or golden cheek whiskers.^[4] In many hylobatid species, striking color phases occur that correlate with sex or ontogeny, a phenomenon prominent in seasonal deciduous forests north of the Isthmus of Kra.^[4][100]

In Nomascus and Hoolock, infants of both sexes are born with pale yellowish or buff fur resembling adult females, which changes to completely black around their first year of life; upon reaching sexual maturity, females undergo a second color transition, shedding dark coats to reacquire pale cream, beige, or golden coats with dark crown streaks, while adult males remain solid black.^[100] In contrast, species such as Hylobates lar and Hylobates agilis display polychromatism with dark-brown and light-tan forms occurring independently of sex.^[4] To amplify their resonant vocalizations, several species possess inflatable throat sacs.^[4][98][105] In the siamang, this laryngeal air sac is hairless, elastic, and voluminous, swelling during calls to a size that rivals the animal's head.^[4][98][105] Smaller, haired laryngeal sacs occur in certain Nomascus and Hylobates species.^[4][105]

Distribution and Habitat

Living hylobatids are confined to the tropical and subtropical forests of East, South, and Southeast Asia.^[106] The western boundary of their distribution is defined by the Brahmaputra River in northeastern India and eastern Bangladesh, extending eastward through Myanmar, southern China, Thailand, Laos, Cambodia, and Vietnam, and southward through Peninsular Malaysia onto the Sunda Shelf islands of Sumatra, Borneo, and Java, as well as the Mentawai Archipelago.^[106][107] Historically, their distribution extended far into mainland China north of the Yangtze and even north of the Yellow River during the Holocene, gradually contracting southward over the past millennium; the sinologist Robert van Gulik attributed their disappearance from most of China to habitat destruction.^{[106][107][108][109]}

The geographical ranges of the four genera exhibit clear allopatric and parapatric zoning across mainland Asia.^[23] Hoolock occupies the westernmost tier, ranging from eastern India, Bangladesh, and Myanmar to Yunnan province in China, bounded to the east by the Salween River.^[23][107] East of the Salween and Mekong, Nomascus predominates, ranging across southern China, Hainan Island, Vietnam, Laos, and eastern Cambodia.^[23][107] Wedged geographically between them, the genus Hylobates extends from southernmost China and southern Myanmar through Thailand, Cambodia, and the Malay Peninsula onto Sumatra, Java, and Borneo.^[23][107] Symphalangus is sympatric with Hylobates, occurring in the montane and lowland forests of Peninsular Malaysia and Sumatra.^[23][107] Certain species are strict insular endemics, such as Hylobates klossii on the Mentawai Islands, Hylobates moloch on Java, Nomascus hainanus on Hainan, and four endemic species on Borneo, including Hylobates muelleri, Hylobates albibarbis, Hylobates abbotti, and Hylobates funereus.^[4][59]

Gibbons occupy a broad spectrum of forest habitats.^[106] In Sundaland, they inhabit dense, evergreen lowland dipterocarp rainforests, but on the mainland they thrive in semi-evergreen, monsoon, and seasonal broadleaf forests.^[106][107] They live up to temperate mountain forests in the Himalayas and, apart from humans and eastern gorillas, reach higher elevations than any other hominoids: hoolock gibbons live up to 2,600 meters and Nomascus species up to 2,900 meters.^[106][110] Siamangs frequently occupy higher, cooler montane forests up to 2,300 meters, while Bornean white-bearded gibbons adapt interchangeably to peat-swamp forests, flooded riverine zones, and montane granite slopes.^[106][110]

Locomotion and Bipedalism

Gibbons are the fastest non-flying, tree-dwelling mammals in the animal kingdom, capable of traveling through tree canopies at speeds up to 55 to 56 km/h.^{[2][111][112]} Their primary mode of travel is brachiation, or ricochetal arm-swinging, propelling the body forward in pendulum-like flight from branch to branch.^[1][3][113] Each swing or arm stride covers approximately 3 meters, and they can cross canopy gaps with leaps exceeding 8 to 10 meters, occasionally reaching 15 meters during dynamic horizontal drops.^{[1][3][114][115][116]} They can also leap vertically upward into branches up to 3.5 meters.^[117] Non-brachiating movements, such as careful climbing along slender peripheral twigs, account for only about 15% of their locomotor repertoire.^[3][23] Larger siamangs employ a more deliberate, pendular swinging gait than the swift, energetic ricochets of dwarf gibbons.^[3]

On sturdy horizontal branches and when descending to the ground, gibbons walk bipedally on two legs, holding their long arms elevated or outstretched to maintain equilibrium.^[1][88][118] They are among the most capable habitual bipeds among non-human primates and are capable of fully extending their knee joints while striding.^[88] Their Achilles tendon architecture and foot mechanics exhibit striking biomechanical convergences with modern humans.^[119] Despite their agility, tree falls resulting from breaking branches or missed grips are frequent hazards; skeletal surveys indicate that the majority of wild gibbons sustain and heal from one or more bone fractures during their lifetimes.^[120][121]

Social Organization and Behavior

The classic social unit across all gibbon species is the territorial, monogamous family group, typically comprising an adult breeding pair and two to four dependent offspring, averaging 3.8 to 4 individuals per group.^[4][122] Monogamy is rare among mammals, found in only about 3% of species, and is thought to have evolved in hylobatids as an adaptation to specialized feeding on small, patchy, and seasonally fluctuating fruit sources that cannot support large congregating troops without prohibitive travel and territorial defense costs.^{[4][122][123]} Within the territory, family members stay closely associated, foraging within a few meters of one another and reinforcing social bonds through daily allogrooming, which occupies roughly 3% of their daily time budget.^[4][124]

Long-term field studies have revealed flexibility in hylobatid mating systems.^[4][125] Extra-pair copulations occur with neighboring territorial residents and transient solitary individuals, and established pairs occasionally divorce.^{[88][125][126][127]} In addition, around 10% of studied groups contain more than two adults.^[128] Polygynous groupings with two or three co-breeding females have been documented in western black crested gibbons (Nomascus concolor) in Yunnan, while polyandrous trios occur in certain populations of lar gibbons and Sumatran siamangs, and in such groups the limit that food availability places on group size may be relaxed.^{[4][23][107][129]}

Gibbon groups defend territories vigorously using visual acrobatic displays, branch breaking, and loud vocalizations, with physical combat remaining rare.^{[106][124][130]} Home ranges average around 35 hectares, of which roughly 75% represents actively defended core territory.^[106] Range sizes vary by species and habitat: silvery gibbons and Thai lar gibbons occupy compact territories of 16 to 17 hectares; siamangs defend 30 to 40 hectares; western hoolock gibbons in Bangladesh occupy 45 hectares or more; and Malaysian lar gibbons living in sympatry with dominant siamangs maintain ranges up to 56 hectares.^[106][122] Siamangs dominate smaller Hylobates species and frequently displace them from coveted fruiting trees.^[23]

Diet and Seed Dispersal

Gibbons are specialized, diurnal frugivores, devoting roughly 57% to 72% of their foraging time to consuming fruit pulp and flowers, with fruit composing roughly 60% to 65% of their total dietary intake.^[131][132] They show a pronounced preference for small, brightly colored, sucrose-rich fruits that are predictably scattered in tree crowns, avoiding direct feeding competition with larger-bodied macaque troops and orangutans by exploiting flexible outer terminal branches.^[4][5] Figs (Ficus) make up about 25% of the fruit gibbons eat, and about 40% in siamangs.^[132] Unlike primates that exhibit bimodal feeding peaks in the early morning and late afternoon, gibbons forage steadily across 9 to 10 active daylight hours, pausing their feeding several hours prior to sunset to retreat into high roost trees.^[106][132]

Diets are supplemented with young tender leaves, shoots, buds, flowers, and animal protein, varying according to local elevation, habitat type, and season.^{[23][131][132]} Siamangs and crested gibbons of the genus Nomascus are the most folivorous hylobatids, relying heavily on leaves and shoots during lean winter periods at high elevations where succulent fruits become scarce.^{[88][107][133][134]} Invertebrates (including insects and spiders), bird eggs, and small vertebrates contribute around 10% of the overall dietary volume in most species.^[131][132] The most distinct dietary divergence occurs in Kloss's gibbon on the Mentawai Islands, where animal protein constitutes up to 25% of its overall food intake.^[88] This adaptation stems from the nutrient-poor soils of the Mentawai archipelago, which cause local plant foliage to produce toxic secondary metabolites, tannins, and chemical defenses, compelling Kloss's gibbon to substitute insects for unpalatable leaves.^[4][132]

Gibbons are ecologically significant primary seed dispersers in Asian forest ecosystems.^[106][135] Because they swallow most small fruits whole, seeds pass intact through the digestive tract and are deposited at distances ranging from 200 to 400 meters, and occasionally up to 1,300 meters, away from parent trees.^[135] However, their role as dispersers has distinct limitations: they can swallow only seeds under 20 mm in diameter, excluding large-seeded trees like wild mangoes, and they favor thin-skinned fruits, preventing them from opening and dispersing hard-husked species such as durian.^[135] Gibbons rarely descend to stagnant forest floor pools to drink, instead obtaining water by licking rainfall from leaves and tree hollows, or by dipping hands into pools and sucking water from their saturated fur.^{[9][136][137]}

Communication and Songs

The vocal displays and morning songs of gibbons are among the most elaborate acoustic signals produced by non-human mammals, carrying through dense forest canopies for distances of 1 to 2 km.^{[106][124][138]} These loud calls serve multiple territorial and social functions, advertising boundary ownership, repelling rival groups, facilitating mate attraction, and strengthening the pair bond between mates.^{[124][138][139]} Acoustic structure is strictly species-specific, sex-specific, and largely innate, allowing researchers and wildlife monitors to accurately identify species, sexes, and specific regional populations solely through acoustic spectrograms.^{[4][124][140]} Calls are concentrated at pure tonal fundamental frequencies between 0.2 and 5 kHz, avoiding ambient jungle noise.^[100]

Gibbon songs are performed as solos and coordinated male-female duets.^{[106][124][138]} Solos are primarily delivered by unpaired adult males at dawn before sunrise, though females also perform solo songs in certain taxa.^[106][124] Siamangs and crested gibbons exhibit complex duets lasting 15 to 30 minutes, though intense vocal bouts occasionally extend up to several hours.^{[100][106][141]} During duets, the female sings a distinctive, rising acceleration of structured notes called the great call, composed of 6 to 100 notes lasting 6 to 30 seconds.^[100][142] The male synchronizes his vocalizations to interleave with the female's strophes, adding acoustic codas and vocal interruptions according to precise temporal rules.^[100][142] In crested gibbons, mothers and immature daughters sing in unison, whereas fathers and sons do not.^[143][144] Two species, the silvery gibbon (Hylobates moloch) and Kloss's gibbon (Hylobates klossii), have secondarily lost coordinated duets and sing exclusively in solos.^[4][100]

Cognition and Intelligence

Gibbons have received less cognitive research attention than great apes, and some authors note that experiments from the first half of the twentieth century may have underestimated their abilities.^[145] Standard laboratory testing apparatus designed for chimpanzees or macaques proved poorly matched to gibbon hand morphology, in which the thumb functions primarily as a tactile sensory digit alongside elongated hook-like fingers.^[145] In spatial memory and canopy-related manipulation tasks, gibbons perform exceptionally well.^[146] In crossed-string puzzle tests requiring subjects to select the correct string linked to a food reward, gibbons equaled or outperformed chimpanzees.^[146] They also succeed in object-permanence experiments, remembering hidden food targets across displaced containers regardless of changing spatial locations.^[146]

In tool-use contexts, gibbons exhibit focused capabilities but notable constraints.^[103] In the wild, they drop dead branches onto intruders and use leafy clumps as sponges to soak up drinking water.^[103] In captivity, they use ropes to assemble swings and can manipulate rakes to pull food rewards closer, recognizing whether a tool carries food and perceiving spatial gaps that interrupt a retrieval path.^[103] However, unlike chimpanzees, they struggle to reorient inverted rakes or manipulate tools in higher-order relation to separate external objects.^[103] Furthermore, gibbons follow gaze cues and use intentional communicative gestures, but they fail the mirror self-recognition mark test and show limited capacity for attributing visual perspectives to others.^[146][147]

Reproduction and Life Cycle

Gibbons reproduce throughout the year without a fixed breeding season, timing conceptions to favorable nutritional conditions.^[4][122] Females experience regular menstrual cycles averaging 28 days in Hylobates lar and 30 days in Hoolock hoolock.^[4][124] Anogenital swelling and color changes during ovulation are slight or absent.^[88] Copulations are typically initiated by the female during estrus and occur in tree branches, usually with the male mounting from behind.^[4][88] Gestation lasts 7 to 7.5 months, and 230 to 235 days have been recorded in the siamang.^[92][124] Females give birth to a single infant; twin births are extremely rare.^[92][124] Birth intervals average two to three years, as lactational amenorrhea suppresses ovulation while mothers nurse.^[122]

Newborn gibbons weigh an average of 406 grams in Hylobates, 487 grams in Nomascus, and 551 grams in Symphalangus, clinging tightly to their mother's belly fur like a belt.^[100][124] Infants remain completely dependent on the mother during their first year, and weaning occurs gradually, concluding between 18 months in lar gibbons and past two years in siamangs.^[4][124] Paternal care varies by species: while adult males contribute little direct carrying in Hylobates, siamang fathers routinely carry infants during their second year of life.^[23] In silvery gibbons, adult males play with older juvenile offspring up to twenty times more frequently than mothers.^[148]

Young gibbons attain adult physical size between 5 and 6 years of age and achieve physiological sexual maturity around 8 to 9 years (though fertile maturity in captivity has been documented as early as 4 to 6 years).^[4][124] Subadults typically disperse from their natal group around 8 to 10 years of age, often forcefully evicted by the resident parent of the same sex.^{[23][124][149]} Dispersing offspring may roam alone for several years as floaters while seeking unoccupied forest patches, with parents sometimes aiding their young by annexing territory or defending adjacent forest parcels.^[106][124] Lifespans in the wild average 25 to 30 years, but gibbons can live longer in captivity, with documented records reaching 44, 50, and 60 years.^{[23][124][150]}

Predators, Parasites, and Diseases

Because gibbons are medium-sized canopy dwellers, their primary natural predators include leopards, clouded leopards, large pythons, and predatory raptors.^[151] Documented predation events remain rare because their rapid brachiation through the high forest canopy makes them difficult to catch.^[151] However, predatory pressure has driven the evolution of sophisticated antipredator strategies, including distinct warning songs, predator mobbing, and an ability to acoustically distinguish between terrestrial felids and aerial raptors.^[151]

Wild gibbons host various gastrointestinal and ectoparasites, including soil-transmitted nematodes that unexpectedly persist despite the animals rarely descending to the forest floor.^[152] A notable health concern is the gibbon ape leukemia virus (GALV; Gammaretrovirus gibleu), a retrovirus closely related to murine leukemia viruses that induces lymphosarcoma and granulocytic leukemia.^[153] Recorded in the 1960s and 1970s in gibbons kept as research or pet animals in Thailand, the United States, and Bermuda, GALV may have been transmitted to gibbons at the SEATO research laboratory in Bangkok, where gibbons were deliberately infected with blood and other tissues from humans, rodents, and other gibbons.^[153]

Conservation Status and Threats

Every hylobatid species is threatened with extinction. As evaluated by the International Union for Conservation of Nature (IUCN), 19 of the 20 extant species are categorized as either Endangered or Critically Endangered, with only the eastern hoolock gibbon (Hoolock leuconedys) evaluated as Vulnerable.^[2][6] The genus Nomascus contains several of the rarest primates on Earth.^[6] The Hainan black crested gibbon (Nomascus hainanus) plummeted from over 2,000 individuals in the late 1950s to just over 20 individuals by 1989, hovering around 17 to 30 individuals in the twenty-first century.^{[154][155][156]} The eastern black crested or Cao Vit gibbon (Nomascus nasutus), long feared extinct, survives in a single fragmented karst forest of only 12 km2 on the China-Vietnam border, totaling roughly 74 individuals across 11 family groups.^[157] On Java, the silvery gibbon (Hylobates moloch) occupies only about 2% of its original forest distribution.^[156]

Deforestation represents the paramount threat to hylobatids across Southeast Asia.^{[2][156][158]} Tropical forests have been decimated by large-scale conversion into commercial monoculture agricultural plantations, notably oil palm and rubber, alongside commercial logging and infrastructure expansion.^[156][158] Because gibbons depend on unbroken tree canopies, forest fragmentation isolates small populations into unviable patches vulnerable to genetic inbreeding depression.^[106][156] Although gibbons exhibit moderate tolerance to low-level selective logging compared to great apes, felling as few as 10 large trees per hectare degrades up to 45% of the surrounding canopy on the Malay Peninsula, triggering severe nutritional stress and forcing gibbons to replace fruit with fibrous leaves.^[4][106]

Poaching and the illegal wildlife trade exert relentless pressure on remaining wild populations.^[156][158] Gibbons are hunted for bushmeat, shot for bone and blood ingredients in traditional folk medicines, and captured alive for the illegal pet trade and tourism entertainment.^{[156][158][159]} Poachers typically shoot adult breeding females to capture nursing infants, causing severe demographic disruption to wild groups.^[158][160] On the black market, live young gibbons have sold for 10 to 500 USD.^[161][162] Between January 2016 and August 2025, over 336 gibbons were seized from traffickers across South and Southeast Asia, with market demand shifting heavily toward India as animals are smuggled from Malaysia, whereas illicit trade previously centered on Indonesia and Vietnam.^[163]

Conservation Initiatives and Captivity

All hylobatid species are listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), prohibiting international commercial trade.^[60][164] In 2015, the IUCN Species Survival Commission Primate Specialist Group declared the Year of the Gibbon, establishing October 24 as International Gibbon Day to mobilize global public awareness.^[165][166] In 2020, international conservation bodies established the Global Gibbon Network to coordinate in situ habitat protection, community patrols, and local environmental education.^[167] Specialized rehabilitation centers, including the Gibbon Rehabilitation Project in Phuket, Thailand, and the Kalaweit Project across Borneo and Sumatra, rescue confiscated pet gibbons and rehabilitate bonded family units for gradual reintroduction into protected forests.^{[168][169][170][171][172]}

Gibbons are widely represented in captive zoological institutions, which housed an estimated 1,462 hylobatids globally by 2011.^[4] Captive reproduction was first recorded at the Rangoon Zoo in 1923, followed by successful zoo births in the United States in 1930 and Europe in 1936.^[3] Regional breeding programs, such as the Gibbon Species Survival Plan (SSP) in North America, manage captive lineages, though captive populations remain heavily biased toward lar gibbons, siamangs, and northern white-cheeked gibbons.^[4][173] Captive propagation faces challenges, including behavioral abnormalities, mate selectivity where pairs reject prospective mates, and an unexplained demographic sex ratio skew where significantly more male infants are born in captivity than females.^[4]

Cultural Significance

Gibbons occupy a venerated status in traditional Asian folklore, mythology, and art, inspired by their human-like upright posture, expressive facial expressions, and haunting vocal duets.^[106][174] In traditional Chinese literature, the character yuan (猿) historically referred specifically to gibbons until modern times.^[108] Early Chinese scholars and poets regarded the gibbon as the noble gentleman (junzi, 君子) of the forest, graceful and aloof in the mountain canopy, in stark contrast to the greedy, terrestrial macaques that stole food from human settlements.^[108] Taoist philosophy attributed supernatural longevity and occult capabilities to gibbons, believing they could live for several hundred or even a thousand years and transform into humans.^[108] Gibbon figurines from the Zhou dynasty date back to the fourth to third centuries BCE, and the apes became celebrated subjects in classical Chinese brush-and-ink painting during the Song, Yuan, and Ming dynasties, immortalized by master painters such as Yi Yuanji, Muqi Fachang, and the Xuande Emperor.^[108][175]

Through the spread of Zen Buddhism and Chinese cultural influence, the artistic motif of the gibbon grasping at the reflection of the moon in the water (Japanese: enkōsokugetsu, 猿猴捉月) became deeply popular in Japanese painting and tea-ceremony ironware, despite gibbons never having occurred naturally in Japan.^{[175][176][177][178]} Drawn from the Mahasamghika Vinaya, the allegory tells of 500 gibbons attempting to rescue the submerged moon by hanging in a chain from an overhanging bough into a deep well; the branch snaps and all drown, warning against foolish, misguided ambition and mistaking illusory desires for reality.^[177][178] Similar gibbon paintings influenced by Chinese art emerged in the Joseon period in Korea, where gibbons were likewise naturally absent.^[176] In Western literature, Dutch diplomat and sinologist Robert van Gulik featured a gibbon in his Judge Dee detective tale 'The Morning of the Monkey', dedicating the story to his beloved pet gibbon Bubu.^[179]

Across Southeast Asia and India, indigenous folklore abounds with mythological explanations for gibbon songs.^[174] In Borneo, legends tell of two runaway lovers fleeing a tyrannical husband who transformed into gibbons, calling constantly through the jungle canopy to find one another.^[174] Communities around Mount Halimun in Java and in northeastern India hold that gibbon cries summon rain from the heavens, or that they fall silent when a human dies.^[174] In Thai folklore, a faithless woman was cursed by Indra to wander the canopy as a gibbon calling perpetually for her husband, giving rise to regional wordplay associating gibbon calls with the Thai word for husband.^[174][180] In Cambodia, a wailing child who ran into the forest out of hunger was said to have become a gibbon, while in Laos, gibbons were revered as reincarnated human ancestors.^[174] Among the Mishmi people of northeastern India, slaying a gibbon is a strict cultural taboo believed to curse the hunter and his family with madness or death.^[174]

On Hainan Island, detailed folklore recorded since the eighteenth century claimed that gibbons perished upon touching the ground unless revived with the juice of monkshood, that females mated with otters, and that gibbons fermented floral rice wine in hidden mountain caves.^[181] Chinese folktales also recounted magical ink monkeys (wuyuan) that hid inside inkwells and drew.^[181] In modern oral history, Hainan villagers preserved a contemporary myth that residents who neglected to cut their hair prior to the communist takeover in 1950 transformed into forest gibbons.^[181] In Vietnamese oral and classical literature, gibbons feature in folk songs such as Ly qua deo and ca dao poetry symbolizing distant, untamed wilderness, as well as in Tu Phu shamanic rituals representing primordial mountain spirits.^[182]

References

1. Schaul, Jordan Carlton (3 March 2014). "Gibbon Conservation Center Working to Save South Asia's Hoolock Gibbons & Other "Small Apes"". National Geographic. Archived from the original on 5 November 2014. Retrieved 14 February 2016.
2. "Gibbon". a-z animals. Retrieved 26 March 2015.
3. DOBRORUKA, Luděk. Poloopice a opice. Praha: SZN, 1979. (Zvířata celého světa; sv. 5). S. 153–160.
4. MITTERMEIER, Russell A.; RYLANDS, Anthony B.; WILSON, Don E. Primates. Barcelona: Lynx Edicions, 2013. (Handbook of the mammals of the World; sv. 3). ISBN 978-84-96553-89-7. S. 754–777. (anglicky)
5. Hutchins, M 2003, p. 211
6. Hylobatidae - Family [online]. IUCN [cit. 2026-03-01]. Dostupné online. (anglicky)
7. Lim, Teckwyn (2020). "An Aslian origin for the word gibbon". Lexis. 15.
8. REJZEK, Jiří. Český etymologický slovník. Voznice: LEDA, 2001, 2012. Heslo gibbon.
9. YERKES, Robert Mearns; YERKES, Ada. The great apes: a study of anthropoid life. New Haven: Yale University Press, 1929. Dostupné online. S. 47–62. (anglicky)
10. Histoire naturelle, générale et particuliére, avec la description du cabinet du Roi. Tome premier \- quinzième! (14). [s.l.] : [s.n.], 1766. 411 s. S. 92.
11. Informations lexicographiques et étymologiques de « Gibbon » dans le Trésor de la langue française informatisé, sur le site du Centre national de ressources textuelles et lexicales.
12. Le Robert de la langue française.
13. (Ingelesez) Gomes, Alberto. (2007-05-16). Modernity and Malaysia: Settling the Menraq Forest Nomads. Routledge ISBN 978-1-134-10077-4. (kontsulta data: 2022-09-23).
14. (Ingelesez) Lim, Teckwyn. (2019-09-02). «An Aslian origin for the word gibbon» Lexis (15) doi:10.4000/lexis.4291. ISSN 1951-6215. (kontsulta data: 2022-09-23).
15. Académie française, « hylobatidés | Dictionnaire de l’Académie française | 9e édition », sur www.dictionnaire-academie.fr (consulté le 8 novembre 2025)
16. THURZO, M. Evolúcia človeka, 1998
17. THURZO, M. Evolúcia človeka. 1998
18. Auliya, Mark André (2006). Taxonomy, Life History and Conservation of Giant Reptiles in West Kalimantan (Indonesian Borneo). Münster, Rhine-Westphalia Utara, Jerman: Natur und Tier - Verlag GmbH. ISBN 3-937285-52-0.
19. Wilkinson 1932, m/s. 643. (Wilkinson, Richard James (1932). A Malay-English dictionary (romanised). II. Mytilini, Yunani: Salavopoulos & Kinderlis – melalui TROVE, Perpustakaan Negara Australia.)
20. Thomas Geissmann & Vincent Nijman (Hanuere 2006). "Calling in Wild Silvery Gibbons (Hylobates moloch) in Java (Indonesia): Behavior, Phylogeny, and Conservation". American Journal of Primatology. 68: 1–19. doi:10.1002/ajp.20203.
21. SPRINGER, Mark S.; MEREDITH, Robert W.; GATESY, John. Macroevolutionary dynamics and historical biogeography of primate diversification inferred from a species supermatrix. PLoS ONE. 2012-11-16, roč. 7, čís. 11, s. e49521. Dostupné online [cit. 2026-03-08]. ISSN 1932-6203. doi:10.1371/journal.pone.0049521. (anglicky)
22. SHAO, Yong; ZHOU, Long; LI, Fang. Phylogenomic analyses provide insights into primate evolution. Science. 2023-06-02, roč. 380, čís. 6648, s. 913–924. Dostupné online [cit. 2026-03-08]. doi:10.1126/science.abn6919. (anglicky)
23. FLEAGLE, John G.; BADEN, Andrea L.; GILBERT, Christopher C. Primate adaptation and evolution. 4. vyd. London, San Diego, Cambridge: Academic Press, 2026. ISBN 978-0-12-815809-8. S. 174–179, 368–371. (anglicky)
24. ZIMA, J.; MACHOLÁN, M. Systém a fylogeneze savců. 1. vyd. Praha: Academia, 2021. 570 s. ISBN 978-80-200-3215-7, ISBN 80-200-3215-0. S. 260–262.
25. SIMPSON, G. G. The principles of classification and a classification of mammals. Bulletin of the AMNH ; v. 85, NY, 1945, S. 67 http://digitallibrary.amnh.org/handle/2246/1104
26. Andrews, P .; Simons, I. «A new Arican Miocene Gibbon-like genus, Dendropithecus (Hominoidea, Primates) with Distinctive postcranial Adaptations: its significance to origin of Hylobatidae». Folia Primatològica, 28, 1977, p. 161-169. DOI: 10.1159 / 000.155.807. PMID: 914.128.
27. Palmer, D.. The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals, 1999, p. 291. ISBN 1-84028-152-9.
28. ALBA, David M.; ALMÉCIJA, Sergio; DEMIGUEL, Daniel. Miocene small-bodied ape from Eurasia sheds light on hominoid evolution. Science. 2015-10-30, roč. 350, čís. 6260. Dostupné online [cit. 2026-03-08]. ISSN 0036-8075. doi:10.1126/science.aab2625. (anglicky)
29. BOUCHET, Florian; ZANOLLI, Clément; URCIUOLI, Alessandro. The Miocene primate Pliobates is a pliopithecoid. Nature Communications. 2024-04-01, roč. 15, čís. 1, s. 2822. Dostupné online [cit. 2026-03-08]. ISSN 2041-1723. doi:10.1038/s41467-024-47034-9. PMID 38561329. (anglicky)
30. GILBERT, Christopher C.; ORTIZ, Alejandra; PUGH, Kelsey D. Additional analyses of stem catarrhine and hominoid dental morphology support Kapi ramnagarensis as a stem hylobatid. Journal of Human Evolution. 2025-02, roč. 199, s. 103628. Dostupné online [cit. 2026-03-08]. doi:10.1016/j.jhevol.2024.103628. (anglicky)
31. Bruce Bower: A stray molar is the oldest known fossil from an ancient gibbon - Ancestors of these small-bodied apes were in India roughly 13 million years ago, a study suggests In: Science News, 8. September 2020. Abgerufen am 9. September 2020 (englisch).
32. Christopher C. Gilbert, Alejandra Ortiz, Kelsey D. Pugh, Christopher J. Campisano, Biren A. Patel, Ningthoujam Premjit Singh, John G. Fleagle, Rajeev Patnaik. New Middle Miocene Ape (Primates: Hylobatidae) from Ramnagar, India fills major gaps in the hominoid fossil record Архивная копия от 1 марта 2021 на Wayback Machine, 2020
33. Дробышевский С. В Индии найден зуб древнейшего гиббона Архивная копия от 17 октября 2020 на Wayback Machine, 20.09.2020
34. Geissmann, T. «Hoolock gibbons get a new genus name» (en anglès). Gibbon Research Lab, 2006. [Consulta: 13 agost 2011].
35. Yumin, G «Preliminary research on the fossil gibbons of the Chinese pléistocène and recent» (en anglès). Human Evol., 1989, p. 509-514. DOI: 10.1007 / BF02436298.
36. Carbone, Lucia; et al. (2014). "Gibbon genome and the fast karyotype evolution of small apes". Nature. 513 (11 September 2014): 195–201. Bibcode:2014Natur.513..195C. doi:10.1038/nature13679. PMC 4249732. PMID 25209798.
37. ROOS, Christian. Phylogeny and classification of gibbons (Hylobatidae). In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 151–165. (anglicky)
38. Hutchins, M 2003, p. 207
39. Matsudaira, K; Ishida, T (May 2010). "Phylogenetic relationships and divergence dates of the whole mitochondrial genome sequences among three gibbon genera". Mol. Phylogenet. Evol. 55 (2): 454–59. Bibcode:2010MolPE..55..454M. doi:10.1016/j.ympev.2010.01.032. PMID 20138221.
40. Geissmann, Thomas (2003). "Taxonomy and evolution of gibbons". Evolutionary Anthropology: Issues, News, and Reviews. 11: 28–31. doi:10.1002/evan.10047. S2CID 36655075.
41. ROOS, Ch. Phylogeny and classification of Gibbons (Hylobatidae). In: REICHARD, U. H. et al. Evolution of Gibbons and Siamang: Phylogeny, Morphology, and Cognition. Springer Verlag, 2016, S. 151-167
42. Shi, Cheng-Min; Yang, Ziheng (January 2018). "Coalescent-Based Analyses of Genomic Sequence Data Provide a Robust Resolution of Phylogenetic Relationships among Major Groups of Gibbons". Molecular Biology and Evolution. 35 (1): 159–179. doi:10.1093/molbev/msx277. PMC 5850733. PMID 29087487.
43. WANG, Sheng; CHEN, Zehui; LUO, Ayun. Genome sequences of extant and extinct gibbons reveal their phylogeny, demographic history, and conservation status. Cell. 2026-01-08, roč. 189, čís. 1, s. 34–51.e20. Dostupné online [cit. 2026-02-25]. ISSN 0092-8674. doi:10.1016/j.cell.2025.10.016. PMID 41205599. (anglicky)
44. Shi, Cheng-Min; Yang, Ziheng (januar 2018). „Coalescent-Based Analyses of Genomic Sequence Data Provide a Robust Resolution of Phylogenetic Relationships among Major Groups of Gibbons”. Molecular Biology and Evolution. 35 (1): 159—179. PMC 5850733 . PMID 29087487. doi:10.1093/molbev/msx277. | //www.ncbi.nlm.nih.gov/pmc/articles/PMC5850733
45. Chatterjee H. J., 2006. Phylogeny and biogeography of gibbons: a dispersal–vicariance analysis. International Journal of Primatology, 27(3), 699–712, doi:10.1007/s10764-006-9044-1
46. CHATTERJE, H. J. Evolutionary relationships among the gibbons: A biogeoghraphic perspective. In: The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology, str. 13 a nasl.
47. ”A complete species-level phylogeny of the Hylobatidae based on mitochondrial ND3–ND4 gene sequences” (pdf). Molecular Phylogenetics and Evolution 36 (2005). 24 mars 2005. sid. 456–467. http://www.gibbons.de/main/papers/pdf_files/2005dna_phylogeny.pdf. Läst 5 april 2010. ”A possible explanation for this lack of resolution may be the fact that despite the early differentiation of gibbons from other apes at approximately 16–23 million years ago (Sibley and Ahlquist, 1987), the subsequent cladogenic events that led to the four distinct genera may have occurred much later and over a very short period of time.”
48. ”Mitochondrial evidence for multiple radiations in the evolutionary history of small apes”. BMC Evolutionary Biology 2010, 10:74. doi:10.1186/1471-2148-10-74. http://www.biomedcentral.com/1471-2148/10/74. ”With up to 16 species, gibbons form the most diverse group of living hominoids, but the number of taxa, their phylogenetic relationships and their phylogeography is controversial. To further the discussion of these issues we analyzed the complete mitochondrial cytochrome b gene from 85 individuals representing all gibbon species, including most subspecies.”
49. Matsudaira, K; Ishida, T. «Phylogenetic relationships and Divergence dates of the whole mitochondrial genome sequences among three Gibbon genera» (en anglès). Mol. Phylogenet. Evol., 5-2010, p. 454-9.
50. THINH, Van Ngoc; MOOTNICK, Alan R.; GEISSMANN, Thomas. Mitochondrial evidence for multiple radiations in the evolutionary history of small apes. BMC Evolutionary Biology. 2010, roč. 10, čís. 1, s. 74. Dostupné online [cit. 2026-03-08]. ISSN 1471-2148. doi:10.1186/1471-2148-10-74. PMID 20226039. (anglicky)
51. WANG, Guiqiang; WU, Yajiang; WANG, Song. Whole-genome sequencing provides insights into the evolutionary adaptation and conservation of gibbons. Journal of Genetics and Genomics. 2026-02-01, roč. 53, čís. 2, s. 269–282. Dostupné online [cit. 2026-03-11]. ISSN 1673-8527. doi:10.1016/j.jgg.2025.07.004. (anglicky)
52. Carbone, L.; Vessere, G. M.; ten Hallers, B. F. H.; Zhu, B.; Osoegawa, K.; Mootnick, A.; Kofler, A.; Wienberg, J.; Rogers, J.; Humphray, S.; Scott, C.; Harris, R. A.; Milosavljevic, A.; de Jong, P. J. (2006). "A high-resolution map of synteny disruptions in gibbon and human genomes". PLOS Genetics. 2 (12) e223. doi:10.1371/journal.pgen.0020223. PMC 1756914. PMID 17196042.
53. CARBONE, Lucia; ALAN HARRIS, R.; GNERRE, Sante. Gibbon genome and the fast karyotype evolution of small apes. Nature. 2014-09-11, roč. 513, čís. 7517, s. 195–201. Dostupné online [cit. 2026-03-08]. ISSN 0028-0836. doi:10.1038/nature13679. PMID 25209798. (anglicky)
54. OKHOVAT, Mariam; NEVONEN, Kimberly A.; DAVIS, Brett A. Co-option of the lineage-specific LAVA retrotransposon in the gibbon genome. Proceedings of the National Academy of Sciences. 2020-08-11, roč. 117, čís. 32, s. 19328–19338. Dostupné online [cit. 2026-03-08]. ISSN 0027-8424. doi:10.1073/pnas.2006038117. PMID 32690705. (anglicky)
55. Michilsens, F.; Vereecke, E. E.; D'Août, K.; Aerts, P. (2009). "Functional anatomy of the gibbon forelimb: Adaptations to a brachiating lifestyle". Journal of Anatomy. 215 (3): 335–354. doi:10.1111/j.1469-7580.2009.01109.x. PMC 2750765. PMID 19519640.
56. Tenaza, R. (1984). "Songs of hybrid gibbons (Hylobates lar × H. muelleri)". American Journal of Primatology. 8 (3): 249–253. doi:10.1002/ajp.1350080307. PMID 31986810. S2CID 84957700.
57. Sugawara, K. (1979). "Sociological study of a wild group of hybrid baboons between Papio anubis and P. hamadryas in the Awash Valley, Ethiopia". Primates 20 (1): 21–56. doi:10.1007/BF02373827
58. Sugawara, K. (1979). "Sociological study of a wild group of hybrid baboons between Papio anubis and P. hamadryas in the Awash Valley, Ethiopia". Primates. 20 (1): 21–56. doi:10.1007/BF02373827. S2CID 23061688.
59. Carl Traeholt (Copenhagen Zoo), Susan Cheyne (WildCRU, Oxford University), Vincent Nijman (BirdLife International): IUCN Red List of Threatened Species: Hylobates funereus. In: IUCN Red List of Threatened Species. 20. November 2015 (iucnredlist.org [abgerufen am 21. September 2025]).
60. Appendices | CITES. Abgerufen am 21. September 2025.
62. GROVES, C. P. Order Primates. In: WILSON, D. E.; REEDER, D. M. Mammal species of the World: a taxonomic and geographic reference. Baltimore: Johns Hopkins University Press, 2005. Dostupné online. ISBN 978-0-8018-8221-0. S. 178–181. (anglicky)
63. LINNÉ, C. von. Car. a Linné Mantissa plantarum : Generum editionis VI. et specierum editionis II. Holmiæ :Impensis Direct. Laurentii Salvii 1767 a 1771. S. 521 521
64. Caroli Illigeri D. Acad. Reg. Scient. Berolinens. et Bavaricae Sod. Museo Zoologico Berolin. praefecti professoris extraord. Prodromus systematis mammalium et avium : additis terminis zoographicis utriusque classis, eorumque versione germanica. Berolini :Sumptibus C. Salfeld,1811, S. 67
65. PRESL, Jan Svatopluk. Ssawectwo. [s.l.] : Kronberger, 1834. 416 s. Dostupné online. S. 134-135, 105.
66. MARTIN, William Charles Linnaeus. A General Introduction to the Natural History of Mammiferous Animals (With a Particular View of the Physical History of Man, and the More Closely Allied Genera of the Order Quadrumana, Or Monkeys). [s.l.] : Wright and Company, printers, 1841. 545 s. Dostupné online. S. 413-445.
67. THENIUS, Erich. Bemerkungen zur taxonomischen und stammesgeschichtlichen Position der Gibbons (Hylobatidae, Primates). Zeitschrift für Säugetierkunde. 1980, roč. 46, s. 232--241. Dostupné online. (německy)
68. GRAY, John Edward. Catalogue of Monkeys, Lemurs and Fruit-eating Bats in the Collection of the British Museum. [s.l.] : British Museum, 1870. 137 s. Dostupné online. S. 4 (a ďalšie strany).
69. BLYTH, Edward. Catalogue of Mammals and Birds of Burma. [s.l.] : S. Austin and sons, 1875. 167 s. Dostupné online. S. 1.
70. THENIUS, E. Bemerkungen zur taxonomischen und stammesgeschichtlichen Position der Gibbons (Hylobatidae, Primates). In: Z.Säugetierkunde 46 (1981) 232-241
71. CARUS, Julius Victor. Handbuch der Zoologie (Wirbelthiere, Mollusken und Molluscoiden). [s.l.] : Engelmann, 1875. 894 s. Dostupné online. S. 73.
72. ARLDT, Theodor. Die Stammesgeschichte der Primaten und die Entwicklung der Menschenrassen. [s.l.] : Springer-Verlag, 2013. 52 s. ISBN 978-3-662-34587-0. S. 27-28.
73. REICHENBACH, H. G. Ludwig. Die vollständigste Naturgeschichte der Affen (Les singes). [s.l.] : Türk, 1863. 204 s. S. 165-167.
74. Mootnick, A.; Groves, C. P. (2005). "A new generic name for the hoolock gibbon (Hylobatidae)". International Journal of Primatology. 26 (4): 971–976. doi:10.1007/s10764-005-5332-4. S2CID 8394136.
75. PROUTY, Leonard A.; BUCHANAN, Philip D.; POLLITZER, William S. Taxonomic note: Bunopithecus: a genus‐level taxon for the hoolock gibbon (Hylobates hoolock). American Journal of Primatology. 1983-01, roč. 5, čís. 1, s. 83–87. Dostupné online [cit. 2026-03-08]. ISSN 0275-2565. doi:10.1002/ajp.1350050110. (anglicky)
76. Primate Taxonomy for the New Millennium [online]. gibbons.de, [cit. 2020-01-05]. Dostupné online.
77. MOOTNICK, Alan; GROVES, Colin. A new generic name for the hoolock gibbon (Hylobatidae). International Journal of Primatology. 2005-08, roč. 26, čís. 4, s. 971–976. Dostupné online [cit. 2026-03-08]. ISSN 0164-0291. doi:10.1007/s10764-005-5332-4. (anglicky)
78. Groves, C.P. 2005. Order Primates. In Wilson, D.E. & Reeder, D.M. (eds.) Mammal Species of the World, Third Edition. The Johns Hopkins University Press, Baltimore. S. 111-184.
79. MEIJAARD, Erik; RAWSON, Benjamin. The phylogenetic species concept and its role in Southeast Asian mammal conservation. In: BEHIE, Alison M.; OXENHAM, Marc F. Taxonomic tapestries: the threads of evolutionary, behavioural and conservation research. Acton: ANU Press, 2015. ISBN 978-1-925022-37-7, ISBN 978-1-925022-36-0. S. 345–360.
80. Ji, Xueping; Harrison, Terry; Zhang, Yingqi; Wu, Yun; Zhang, Chunxia; Hu, Jinming; Wu, Dongdong; Hou, Yemao; Li, Song; Wang, Guofu; Wang, Zhenzhen (2022-10-01). "The earliest hylobatid from the Late Miocene of China". Journal of Human Evolution. 171 103251. Bibcode:2022JHumE.17103251J. doi:10.1016/j.jhevol.2022.103251. ISSN 0047-2484. PMID 36113226. S2CID 252243877.
81. Harrison, Terry. (2016). The Fossil Record and Evolutionary History of Hylobatids. In: REICHART, U. H. et al. Developments in Primatology: Progress and Prospects -Evolution of Gibbons and Siamang, 2016, str. 91 a nasl. ISBN 978-1-4939-5614-2
82. Результаты поиска по запросу «Hylobatidae» на сайте ASM Mammal Diversity Database Архивная копия от 28 октября 2020 на Wayback Machine.
83. TURVEY, S. T. et al. New genus of extinct Holocene gibbon associated with humans in Imperial China. In: Science 22 June 2018
84. (en) Sheng Wang, Zehui Chen, Ayun Luo et Xinran You, « Genome sequences of extant and extinct gibbons reveal their phylogeny, demographic history, and conservation status », Cell, vol. 0, no 0,‎ 7 novembre 2025 (ISSN 0092-8674 et 1097-4172, DOI 10.1016/j.cell.2025.10.016, lire en ligne, consulté le 8 novembre 2025)
85. Brown, Georgia (11 January 2017). "New species of gibbon discovered in China". The Guardian. Retrieved January 13, 2021.
86. Sonstige, Wilson, Don E. 1944- Hrsg. Cavallini, Paolo (2013). Handbook of the mammals of the world. Lynx Edicions. ISBN 978-84-96553-89-7. OCLC 1222638259.
87. 13-Million-Year-Old Gibbon Ancestor Discovered in India, auf sci-news vom 9. September 2020
88. VANČATA, Václav. Primatologie – Díl 2. Catarrhina - opice a lidoopi. Praha: Univerzita Karlova, 2003. S. 108–121.
89. NOWAK, Ronald M. Walker's primates of the World. Baltimore: Johns Hopkins University Press, 1999. Dostupné online. S. 168.
90. REICHARD, Ulrich H.; PREUSCHOFT, Holger. Why is the siamang larger than other hylobatids?. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 169–183. (anglicky)
91. «ARKive: Siamang (Symphalangus syndactylus)». Arhivēts no oriģināla, laiks: 2013. gada 22. septembrī. Skatīts: 2014. gada 8. aprīlī. Arhivēts 2013. gada 22. septembrī, Wayback Machine vietnē.
92. ANDĚRA, Miloš. Savci (1). Praha: Albatros, 1997. (Svět zvířat; sv. 1). S. 132–134.
93. «Bristol Zoo: Agile gibbon». Arhivēts no oriģināla, laiks: 2014. gada 18. jūnijā. Skatīts: 2014. gada 8. aprīlī.
94. VAUGHAN, Terry A.; RYAN, James M.; CZAPLAWSKI, Nicholas J. Mammalogy. 6. vyd. Burlington, MA: Jones & Bartlett Learning, 2015. S. 181. (anglicky)
95. Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. «Family Hylobatidae gibbons and lesser apes» (en anglès), 2008. [Consulta: 13 agost 2011].
96. Ankel-Simons, F. 2007, p. 316
97. Ankel-Simons, F. 2007, p. 328
98. Lull, Richard Swann (1921). "Seventy Seven". Organic Evolution. New York: The Macmillan Company. pp. 641–677.
99. Ankel-Simons, F. 2007, p. 346
100. Geissmann, T. (2011). "Typical Characteristics". Gibbon Research Lab. Retrieved 17 August 2011.
101. Nowak, RM 1999, p. 168
102. Ankel-Simons, F. 2007, p. 274
103. CUNNINGHAM, Clare L.; ANDERSON, James R.; MOOTNICK, Alan R. The evolution of technical intelligence: perspectives from the Hylobatidae. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 291–311. (anglicky)
104. Ankel-Simons, F. 2007, p. 150
105. Ankel-Simons, F. 2007, p. 442
106. HUTCHINS, M.; KLEIMAN, D. G.; GEIST, V.; MCDADE, M. C. Mammals III. 2. vyd. Farmington Hills, MI: Gale, 2003. (Grzimek's animal life encyclopedia; sv. 14). S. 207–215. (anglicky)
107. Hutchins, M 2003, p. 210
108. van Gulik, Robert. "The gibbon in China. An essay in Chinese animal lore." E. J. Brill, Leiden, Holland. (1967). Brief summary
109. Cyril C. Grueter, Xuelong Jiang, Roger Konrad, Pengfei Fan, Zhenhua Guan, Thomas Geissmann: Are Hylobates lar Extirpated from China? In: International Journal of Primatology, August 2009, Volume 30, Issue 4, S. 553–567. doi:10.1007/s10764-009-9360-3
110. REICHARD, Ulrich H.; BARELLI, Claudia; HIRAI, Hirohisa. The evolution of gibbons and siamang. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 3–41. (anglicky)
111. «Gibbon Conservation Center» (en anglès). Arxivat de l'original el 23 de març 2010. [Consulta: 22 setembre 2011].
112. «Asian Apes». Arhivēts no oriģināla, laiks: 2014. gada 2. augustā. Skatīts: 2014. gada 8. aprīlī.
113. Ankel-Simons, F. 2007, p. 381
114. Nowak, RM 1999, p. 169
115. , Temporada:1 , episodi:8. « »
116. Nationalgeographic: Gibbon Hylobatidae
117. The extraordinary athletic performance of leaping gibbons[novecojusi saite]
118. Ankel-Simons, F. 2007, p. 149
119. Aerts, P.; d'Août, K.; Thorpe, S.; Berillon, G.; Vereecke, E. (2018). "The gibbon's Achilles tendon revisited: consequences for the evolution of the great apes?". Proceedings of the Royal Society B. 285 (1880) 20180859. doi:10.1098/rspb.2018.0859. PMC 6015853. PMID 29899076.
120. Attenborough, David. Life of Mammals, "Episode 8: Life in the Trees", BBC Warner, 2003.
121. David Attenborough, Life of Mammals, Episode 8: Life in the Trees. BBC Warner, 2003.
122. Hutchins, M 2003, p. 213
123. «What are Gibbons?». Arhivēts no oriģināla, laiks: 2014. gada 6. jūnijā. Skatīts: 2014. gada 8. aprīlī.
124. Nowak, RM 1999, p. 171
125. Reichard, U (1995). "Extra-pair copulations in a monogamous gibbon (Hylobates lar)". Ethology. 100 (2): 99–112. Bibcode:1995Ethol.100...99R. doi:10.1111/j.1439-0310.1995.tb00319.x.
126. Briggs, Mike; Briggs, Peggy (2005). The Encyclopedia of World Wildlife. Parragon. p. 146. ISBN 978-1-4054-5680-7.
127. BARELLI, Claudia; MATSUDAIRA, Kazunari; WOLF, Tanja. Extra‐pair paternity confirmed in wild white‐handed gibbons. American Journal of Primatology. 2013-12, roč. 75, čís. 12, s. 1185–1195. Dostupné online [cit. 2026-03-15]. ISSN 0275-2565. doi:10.1002/ajp.22180. (anglicky)
128. Fuentes, Agustin (2000). "Hylobatid communities: Changing views on pair bonding and social organization in hominoids". American Journal of Physical Anthropology. 113 (S31): 33–60. doi:10.1002/1096-8644(2000)43:31+<33::AID-AJPA3>3.0.CO;2-D. ISSN 1096-8644. PMID 11123837.
129. Malone, Nicholas; Fuentes, Agustin (2009), "The Ecology and Evolution of Hylobatid Communities: Causal and Contextual Factors Underlying Inter- and Intraspecific Variation", in Whittaker, Danielle; Lappan, Susan (eds.), The Gibbons: New Perspectives on Small Ape Socioecology and Population Biology, New York, NY: Springer, pp. 241–264, doi:10.1007/978-0-387-88604-6_12, ISBN 978-0-387-88604-6, retrieved 2024-12-03
130. Nowak, R.M., 1999, p. 171
131. Gibbon - Monkey Worlds Retrieved Feb-12-2015
132. Hutchins, M 2003, p. 212
133. Dao-Ying, Lan (1993-02-08). "Feeding and Vocal Behaviours of Black Gibbons (Hylobates concolor) in Yunnan: A Preliminary Study". Folia Primatologica. 60 (1–2): 94–105. doi:10.1159/000156679. ISSN 1421-9980. PMID 8335299.
134. Bleisch, William V.; Chen, Nan (1991-10-01). "Ecology and behavior of wild black-crested gibbons (Hylobates concolor) in China with a reconsideration of evidence for polygyny". Primates. 32 (4): 539–548. doi:10.1007/BF02381946. ISSN 1610-7365.
135. MCCONKEY, Kim R. Seed dispersal by primates in asian habitats: from species, to communities, to conservation. International Journal of Primatology. 2018-06, roč. 39, čís. 3, s. 466–492. Dostupné online [cit. 2026-03-14]. ISSN 0164-0291. doi:10.1007/s10764-017-0013-7. (anglicky)
136. Edward Osborne Wilson: Socjobiologia. Poznań: Zysk i S-ka Wydawnictwo s.c., 2001. ISBN 83-7150-682-1.
138. Clarke E, Reichard UH, Zuberbühler K (2006). Emery N (ed.). "The Syntax and Meaning of Wild Gibbon Songs". PLOS ONE. 1 (1) e73. Bibcode:2006PLoSO...1...73C. doi:10.1371/journal.pone.0000073. PMC 1762393. PMID 17183705.
139. FELDHAMER, G. A.; MERRITT, J. F.; KRAJEWSKI, C. & kol. Mammalogy: adaptation, diversity, ecology. 5. vyd. Baltimore, Maryland: Johns Hopkins University Press, 2020. ISBN 978-1-4214-3652-4, ISBN 978-1-4214-3653-1. S. 321. (anglicky)
140. Glover, Hilary. Recognizing gibbons from their regional accents Archived 2021-02-27 at the Wayback Machine, BioMed Central, EurekAlert.org, 6 February 2011.
141. 『動物大百科3』 p126
142. Geissmann, Thomas (maj 2009). ”Door slamming: Tool-use by a captive white-handed gibbon (Hylobates lar)”. Gibbon Journal Issue No. 5. Gibbon Conservation Alliance (www.gibbonconservation.org). sid. 53–60. Arkiverad från originalet den 14 september 2012. https://web.archive.org/web/20120914005249/http://www.gibbonconservation.org/07_journal/gibbon_journal_5.pdf. Läst 17 april 2010. ”A typical cycle of events occurring several times in a gibbon duet song bout begins with male short phrases (often accompanied by female short phrases), followed by the onset of a female great-call. The male falls silent during the build-up phase of the great-call and adds a coda at the climax. After that, he resumes the production of short phrases (again, with or without female short phrases).”
143. KODA, Hiroki. Gibbon songs: understanding the evolution and development of this unique form of vocal vommunication. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 349–359. (anglicky)
144. KODA, Hiroki; LEMASSON, Alban; OYAKAWA, Chisako. Possible role of mother-daughter vocal interactions on the development of species-specific song in gibbons. PLoS ONE. 2013-08-12, roč. 8, čís. 8, s. e71432. Dostupné online [cit. 2026-03-15]. ISSN 1932-6203. doi:10.1371/journal.pone.0071432. PMID 23951160. (anglicky)
145. PRIME, Jacqueline M.; FORD, Susan M. Hand manipulation skills in hylobatids. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 269–289. (anglicky)
146. TOMASELLO, Michael; CALL, Josep. Primate cognition. New York: Oxford University Press 517 s. ISBN 978-0-19-510623-7, ISBN 978-0-19-510624-4. S. 48–49, 80–81, 111, 120, 333. (anglicky)
147. LIEBAL, Katja. Communication and cognition of small apes. In: REICHARD, Ulrich H.; HIRAI, Hirohisa; BARELLI, Claudia. Evolution of gibbons and siamang: phylogeny, morphology, and cognition. New York: Springer, 2016. ISBN 978-1-4939-5614-2. S. 313–347. (anglicky)
148. YI, Yoonjung; MARDIASTUTI, Ani; CHOE, Jae C. How to be a good partner and father? The role of adult males in pair bond maintenance and parental care in Javan gibbons. Proceedings of the Royal Society B: Biological Sciences. 2023-06-28, roč. 290, čís. 2001. Dostupné online [cit. 2026-03-15]. ISSN 0962-8452. doi:10.1098/rspb.2023.0950. PMID 37369349. (anglicky)
149. Jerzy A. Kowalski: Homo eroticus. Opole: Wydawnictwo IBS, 2011, s. 18, seria: Eros i logos. ISBN 978-83-931776-0-8.
150. GEISSMANN, T.; GESCHKE, K.; BLANCHARD, B. J. Longevity in gibbons (Hylobatidae). Gibbon Journal. 2009, roč. 5, s. 81–91. Dostupné online [cit. 2026-04-01]. doi:10.5167/UZH-20115.
151. CLARKE, Esther; REICHARD, Ulrich H.; ZUBERBÜHLER, Klaus. The anti-predator behaviour of wild white-handed gibbons (Hylobates lar). Behavioral Ecology and Sociobiology. 2012-01-01, roč. 66, čís. 1, s. 85–96. Dostupné online [cit. 2026-03-15]. ISSN 1432-0762. doi:10.1007/s00265-011-1256-5. (anglicky)
152. MALINTAN, Rizka; SUPIYANI, Atin; OKTAVIANI, Rahayu. Endoparasites of wild Javan Gibbon (Hylobates moloch) at Gunung Halimun Salak National Park, Indonesia. HAYATI Journal of Biosciences. 2024-06-12, roč. 31, čís. 5, s. 929–941. Dostupné online [cit. 2026-03-15]. ISSN 2086-4094. doi:10.4308/hjb.31.5.929-941. (anglicky)
153. BROWN, Katherine; TARLINTON, Rachael E. Is gibbon ape leukaemia virus still a threat?. Mammal Review. 2017-01, roč. 47, čís. 1, s. 53–61. Dostupné online [cit. 2026-03-16]. ISSN 0305-1838. doi:10.1111/mam.12079. (anglicky)
154. GEISSMANN, T.; BLEISCH, W. Nomascus hainanus [online]. The IUCN Red List of Threatened Species, 2020 [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2025-05-07. (anglicky)
155. Hainan gibbon conservation [online]. zsl.org [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2026-02-17. (anglicky)
156. «Lesser Apes» (en anglès). Conservation Internacional. Arxivat de l'original el 2013-11-05. [Consulta: 13 agost 2011].
157. WEARN, O. R.; FAN, Pengfei. Cao-vit gibbon. In: Russell A. Mittermeier, Kim E. Reuter, Anthony B. Rylands, Andie Ang, Leandro Jerusalinsky, Stephen D. Nash, Christoph Schwitzer, Jonah Ratsimbazafy & Tatyana Humle. Primates in peril: The World’s 25 most endangered primates 2023–2025. Washington, DC.: IUCN SSC Primate Specialist Group (PSG), International Primatological Society (IPS) and Re:wild, 2024. ISBN 979-8-218-44952-0. S. 87–91. (anglicky)
158. Threats [online]. Gibbon SSP [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2025-09-15. (anglicky)
159. «The Gibbon Trade» (en anglès). Conservation Internacional, 01-11-2007. Arxivat de l'original el 2013-11-05. [Consulta: 13 agost 2011].
160. gibbon rehabilitation project
161. CHEYNE, Sm. Challenges and opportunities of primate rehabilitation – gibbons as a case study. Endangered Species Research. 2009-10-05, roč. 9, s. 159–165. Dostupné online [cit. 2026-03-01]. ISSN 1863-5407. doi:10.3354/esr00216. (anglicky)
162. Cheyne, SM «Challenges and opportunities of primate rehabilitation - Gibbons as a case study» (en anglès). Endangered Species Research, 9, 2009, p. 159-165. Arxivat de l'original el 2018-10-24 [Consulta: 7 juny 2021].
163. Gibbons in peril as trafficking peaks. traffic.org [online]. 2025-10-24 [cit. 2026-03-01]. Dostupné online. (anglicky)
164. Hylobatidae [online]. CITES [cit. 2026-03-16]. Dostupné online. (anglicky)
165. Mittermeier, Russell. "Letter of Endorsement - Year of the Gibbon" (PDF). IUCN SSC PSG Section on Small Apes. IUCN SSC Primate Specialist Group. Archived from the original (PDF) on 4 March 2016. Retrieved 30 July 2015.
166. International Gibbon Day: Learn more to protect more [online]. news.cgtn.com, 2022-10-24 [cit. 2026-04-01]. Dostupné v archivu pořízeném z originálu dne 2024-11-07. (anglicky)
167. Establishment of the Global Gibbon Network Initiative. iucn.org [online]. 2020-12-17 [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2026-01-16. (anglicky)
168. "The Gibbon Rehabilitation Project".
169. "Projets". Kalaweit (in French). Retrieved 2023-05-09.
170. ŠUSTA, František. Rehabilitační stanice pro gibony lary. Živa. 2005, čís. 3, s. 135–136. Dostupné online.
171. Kalaweit à Bornéo.
172. https://www.kalaweit.org/sites-kalaweit-sumatra.php Kalaweit à Sumatra].
173. The Gibbon SSP [online]. Gibbon SSP [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2026-01-05. (anglicky)
174. Tales of the gibbons [online]. gibbons.asia [cit. 2026-03-01]. Dostupné v archivu pořízeném z originálu dne 2024-08-13. (anglicky)
175. Geissmann, Thomas. "Gibbon paintings in China, Japan, and Korea: Historical distribution, production rate and context" Archived 2008-12-17 at the Wayback Machine, Gibbon Journal, No. 4, May 2008. (includes color reproductions of a large number of gibbon paintings by many artists)
176. GEISSMANN, Thomas. Gibbon paintings in China, Japan, and Korea: historical distribution, production rate and context. Gibbon Journal. 2008, roč. 4, s. 1–38. Dostupné v archivu pořízeném z originálu dne 2008-12-17. (anglicky)
177. 山下善也「ほほ笑みのお猿 山雪の猿猴図」 - 東京国立博物館、2022年10月5日閲覧。
178. 影山純夫『禅画を読む』淡交社 2011年、ISBN 9784473037268 pp.118-121
179. VAN GULIK, R. The monkey and the tiger. Chicago: University of Chicago Press, 1992. Dostupné online. (anglicky)
180. ฟ้าวันใหม่สุดสัปดาห์ 310 05 58 เบรก 2
181. TURVEY, Samuel T.; BRYANT, Jessica V.; MCCLUNE, Katherine A. Differential loss of components of traditional ecological knowledge following a primate extinction event. Royal Society Open Science. 2018-06, roč. 5, čís. 6, s. 172352. Dostupné online [cit. 2026-03-01]. ISSN 2054-5703. doi:10.1098/rsos.172352. PMID 30110450. (anglicky)
182. "Bản sao đã lưu trữ". Bản gốc lưu trữ ngày 21 tháng 9 năm 2014. Truy cập ngày 18 tháng 4 năm 2011.