Animal Diversity Web

Ge­o­graphic Range

The en­tire pop­u­la­tion of the Hainan black-crested gib­bon, No­mas­cus hainanus, is found in the 300 km^2 Bawan­gling Na­tional Na­ture Re­serve (BNNR) on Hainan Is­land off of the coast of China. His­tor­i­cally, N. hainanus was wide­spread on Hainan Is­land but a re­cent es­ti­mate put its en­tire ge­o­graphic range as low as 14 to 16 km^2 of BNNR. (Zhang, et al., 2010; Zhou, et al., 2005)

• Biogeographic Regions
• oriental
  • native

• Other Geographic Terms
• island endemic

Habi­tat

Hainan black-crested gib­bons live in trop­i­cal pri­mary forests. It is es­ti­mated that 95% of their orig­i­nal habi­tat has been lost. Hainan black-crested gib­bons re­quire in­dige­nous for­est of Hainan Is­land and do not in­habit re­cently planted pine forests or rub­ber plan­ta­tions. Due to habi­tat loss and hunt­ing, this species has shifted its pri­mary habi­tat from low­land for­est to higher moun­tain­ous for­est (with el­e­va­tions rang­ing from 100 to 1800 m on Hainan Is­land). Op­ti­mal habi­tat is hard to de­ter­mine as a re­sult of the small pop­u­la­tion size and al­tered en­vi­ron­ment on the en­tire is­land. How­ever, ma­ture, ravine trop­i­cal forests, in par­tic­u­lar, seem to be fa­vored. Like other gib­bons, Hainan black-crested gib­bons are spe­cial­ized for liv­ing in the canopies of forests. (Zhang, et al., 2010; Zhou, et al., 2008)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest
• mountains

• Range elevation

  100 to 1800 m

  328.08 to 5905.51 ft

Phys­i­cal De­scrip­tion

Adult males and ju­ve­niles have com­pletely black pelage while fe­males are brown­ish buff with some black hairs ap­pear­ing on the limbs as they age. Males and fe­males have a large black crest of fur on the top of their heads. The crest is ap­prox­i­mately 10 by 3 cm. Fe­males also have a char­ac­ter­is­tic white face ring. In­fants are born tawny brown, be­com­ing black within 5 to 6 months. (Liu, et al., 1989; Moot­nick and Fan, 2011)

Adults weigh be­tween 5.8 and 10 kg. Hind limbs are 70.4% the length of fore­limbs, which is slightly longer than in other black-crested gib­bons (No­mas­cus species). The in­teror­bital dis­tance ranges from 10.4 to 10.7 mm. Along with pelage col­oration, phys­i­cal size is the main iden­ti­fy­ing char­ac­ter­is­tic of No­mas­cus species. Due to the rar­ity of Hainan black-crested gib­bons, very few spec­i­mens have been col­lected and lit­tle is known of vari­a­tion in size. How­ever, within gib­bons there is lit­tle vari­a­tion in body size. Most likely N. hainanus has a sim­i­lar body length as other gib­bons and this as­sump­tion is sup­ported by anec­do­tal ev­i­dence (Pocock 1905). Lar gib­bons (Hy­lo­bates lar) are re­ported to reach an adult size of 42 to 60 cm in length (ex­clud­ing the tail). (Ma, et al., 1988; Pocock, 1905; Uh­len­broek, 2011; Zihlman, et al., 2011)

There is no sex­ual di­mor­phism in size in gib­bons. How­ever, there is sex­ual di­mor­phism in col­oration, also known as sex­ual dichro­ma­tism. (Bleisch and Chen, 1991; Leigh and Shea, 1995)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently

• Range mass

  5.8 to 10 kg

  12.78 to 22.03 lb

Re­pro­duc­tion

So­cial polyg­yny, with two fe­males and a sin­gle male, is the usual mat­ing sys­tem in N. hainanus. Fe­males ini­ti­ate mat­ing by ap­proach­ing a male and mov­ing their head and limbs in rhyth­mic, jerky mo­tions. Mul­ti­ple cop­u­la­tions via dorsoven­tral mount­ing may occur in a sin­gle day. Sex­u­ally ac­tive fe­males oc­ca­sion­ally en­gage in post-con­cep­tion cop­u­la­tion, which is rel­a­tively rare amongst the pri­mates. (Zhou, et al., 2008)

• Mating System
• polygynous

The amount of time be­tween births is ap­prox­i­mately 24 months. This tim­ing may be caused by bian­nual fruit­ing of many fa­vored food sources and thus link re­pro­duc­tion with the abun­dance of food. Two fe­males in a sin­gle so­cial group may rear off­spring from the same male at the same time. Ges­ta­tion has been es­ti­mated to be 136 to 173 days. (Moot­nick, et al., 2012; Zhou, et al., 2008)

• Key Reproductive Features
• iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

• Breeding interval

  Nomascus hainanus females give birth every second year.

• Breeding season

  Breeding season is not reported in the literature.

• Average number of offspring

  1

• Range gestation period

  136 to 173 days

In­fants are de­pen­dent on their mother for the first 1.5 years of their lives, but re­main in the so­cial group as ju­ve­niles for some time after this. It is dur­ing this in­fant de­pen­dency pe­riod where lac­ta­tion oc­curs. Lac­ta­tion is en­er­get­i­cally costly for fe­male gib­bons of other species. (Lap­pan, 2009; Zhou, et al., 2008)

In one case, a ma­tur­ing male off­spring was dri­ven out of the group at 5.5 years of age. This is quite early com­pared to most other gib­bon species, which ma­ture from 6 to 9 years. A pos­si­ble rea­son for this evic­tion, be­sides ac­tual sex­ual ma­tu­rity is that, due to lim­ited re­sources, the alpha male may have been forced to drive out the ma­tur­ing off­spring. (Tilsen, 1979; Zhou, et al., 2008)

• Parental Investment
• female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifes­pan/Longevity

Al­though lifes­pan data is lim­ited due to their rar­ity, gib­bons live longer than most other pri­mates, with a record of 60 years in a Hy­lo­bates muel­leri in­di­vid­ual. Lifes­pan is not re­ported in No­mas­cus hainanus. (Geiss­man, et al., 2009)

Be­hav­ior

Hainan black-crested gib­bons are found in so­cial groups com­posed of fe­males, ju­ve­niles, in­fants and, oc­ca­sion­ally, males. Males will also live soli­tar­ily. Group size has been hard to de­ter­mine due to the ex­tremely low pop­u­la­tion size and fluc­tu­a­tions in be­hav­ior of N. hainanus as a re­sult of the degra­da­tion of habi­tat. (Zhou, et al., 2005)

The most com­mon form of lo­co­mo­tion in a closely re­lated species of black crested gib­bon (No­mas­cus con­color con­color) is brachi­a­tion (rapid swing­ing from branch to branch via the fore­limbs) through the canopy. Leap­ing, walk­ing and climb­ing were also ob­served but the gib­bons were never seen to come to the ground. Brachi­a­tion has also been ob­served in N. hainanus. (Haimoff, 1984; Haimoff, 1987)

• Key Behaviors
• arboreal
• scansorial
• diurnal
• motile
• sedentary
• social

Home Range

No­mas­cus hainanus in­di­vid­u­als oc­cupy home ranges of 200 to 500 hectares (2 to 5 km^2), which are the largest home range sizes of any gib­bon. How­ever, this large size might be the re­sult of re­duced in­traspe­cific com­pe­ti­tion or in­creased area be­tween suit­able food patches. It is sug­gested that home range size might re­cently have in­creased to nearly 1000 hectares (10 km^2) due to degra­da­tion of habi­tat qual­ity. (Zhang, et al., 2010; Zhou, et al., 2005; Zhou, et al., 2008)

Com­mu­ni­ca­tion and Per­cep­tion

Hainan black-crested gib­bons often per­form morn­ing duets be­tween male and fe­male pairs. The fe­male usu­ally only emits a sin­gle loud noise often re­ferred to as a great-call. The male’s song is more elab­o­rate and has at least three dis­tinct calls. The pres­ence of a la­ryn­geal sac in males may con­tribute to the in­creased com­plex­ity of vo­cal­iza­tions. Hainan black-crested gib­bons are be­lieved to be the only gib­bon species with a male dom­i­nated duet. (Haimoff, 1984)

Hainan black-crested gib­bons are one of only three gib­bon species in which the fe­male makes vo­cal­iza­tions dur­ing mat­ing. There are many hy­pothe­ses con­cern­ing these soft grunts of the fe­male but it might have be re­lated to the so­cial polyg­yny of N. hainanus and it may be an ad­ver­tise­ment of ovu­la­tion to other fe­males. (Zhou, et al., 2008)

• Communication Channels
• visual
• acoustic
• chemical

• Other Communication Modes
• duets

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Hainan black-crested gib­bons are al­most ex­clu­sively fru­gi­vores. In the refuge they in­habit, the most com­mon food sources are the fruits from Litchi ca­nen­sis, Nephelium topengii, and var­i­ous Ficus species. Figs in par­tic­u­lar have been noted as a fa­vored food source. Closely re­lated species of gib­bons eat in­sects, seeds, and grains and N. hainanus may have a sim­i­lar diet. (Mc­Conkey, 2005; Zhou, et al., 2008)

• Primary Diet
• herbivore
  • frugivore

• Animal Foods
• insects

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit

Pre­da­tion

Tree se­lec­tion for sleep­ing is an an­tipreda­tor be­hav­ior for gib­bons. They often sleep in the tallest trees in an area which would safe­guard them from most ter­res­trial preda­tors. Gib­bons also sleep on branches with many twigs so that the twigs, which vi­brate eas­ily, will act as an early warn­ing sys­tem. Hainan black-crested gib­bons were not ex­plic­itly men­tioned in a Fei et al. 2012 study, but these in­sights into their close rel­a­tives, N. na­su­tus, may hold true for them as well. (Fei, et al., 2012)

Two at­tacks from an uniden­ti­fied species of hawk last­ing ap­prox­i­mately 15 min­utes have been ob­served on N. hainanus. A species sur­vey of Hainan Is­land recorded 7 species of car­niv­o­rous ea­gles and hawks. (Li, et al., 2013; Zhou, et al., 2005)

Hu­mans are the main preda­tors of Hainan black-crested gib­bons. Hu­mans can ben­e­fit by sell­ing adults into the il­le­gal an­i­mal trade, use the meat for food, or sell the bones for use in tra­di­tional Chi­nese med­i­cine. Mass slaugh­ters have been recorded on nu­mer­ous oc­ca­sions. (Zhou, et al., 2005)

• Known Predators

  • humans (Homo sapiens)

Ecosys­tem Roles

Hainan black-crested gib­bons have been de­scribed as an um­brella species for the local ecosys­tem. An um­brella species is one which in­di­cates the over­all health of an ecosys­tem. Gib­bons may also play a role in the seed dis­per­sal of many of the fruits that they eat. (Mc­Conkey, 2005; Zhang, et al., 2010)

• Ecosystem Impact
• disperses seeds

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Hainan black-crested gib­bons can act as seed dis­persers for for­est tree species. Trade in live N. hainanus as well as body parts, can re­sult in hefty prof­its from black mar­ket Chi­nese med­i­cine. There is no proven ef­fi­cacy of these tra­di­tional "med­i­cines" and the im­pact on wildlife pop­u­la­tions is dev­as­tat­ing. (Mc­Conkey, 2005; Zhou, et al., 2005)

• Positive Impacts
• source of medicine or drug

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Due to the crit­i­cally en­dan­gered sta­tus of Hainan black-crested gib­bons, the Chi­nese gov­ern­ment has put a ban on all types of forestry in or around BNNR. Hainan Is­land, which is home to many in­tro­duced rub­ber plan­ta­tions, has been forced to stop the ex­pan­sion of the rub­ber in­dus­try in order to save N. hainanus and other en­dan­gered species. This is a short-term neg­a­tive eco­nomic im­pact, but has long-term pos­i­tive im­pacts be­cause it helps to pro­tect a crit­i­cal and unique ecosys­tem. (Zhou, et al., 2005; Zhou, et al., 2008)

Con­ser­va­tion Sta­tus

The IUCN cur­rently lists Hainan black-crested gib­bons as crit­i­cally en­dan­gered. Some have sug­gested that they are the rarest mam­mals in the world, with ap­prox­i­mately 20 in­di­vid­u­als counted in a re­cent sur­vey. A major con­cern is that of the ap­prox­i­mately 20 in­di­vid­u­als left, only 4 are adult fe­males and one of these may be post-re­pro­duc­tive. Num­bers have in­creased since 2003, when it was be­lieved that there were as few as 13 in­di­vid­u­als. (Moot­nick, et al., 2012; Zhou, et al., 2005)

Con­ser­va­tion ef­forts are var­ied. Tech­nolo­gies such as re­mote sens­ing and ge­o­graphic in­for­ma­tion sys­tems are being used to de­ter­mine suit­able habi­tats. The gov­ern­ment is also plan­ning on adding to the list of pro­tected for­est on Hainan Is­land. In 2003, the Hainan Gib­bon Ac­tion Plan was launched. Pop­u­la­tion sur­veys, re­for­esta­tion, and the train­ing of staff to mon­i­tor the gib­bons are all parts of the Ac­tion Plan. (Moot­nick, et al., 2012; Zhang, et al., 2010)

Habi­tat loss and human en­croach­ment and ac­tiv­ity are the main rea­sons for the de­cline in pop­u­la­tion of Hainan black-crested gib­bons. The species has seen a dras­tic re­duc­tion in range and pop­u­la­tion since the 1950s. The an­nual rate of habi­tat loss is ap­proach­ing zero, al­though more work needs to be done con­cern­ing crit­i­cal habi­tat con­ser­va­tion, but Hainan black-crested gib­bons are, with­out a doubt, on the very edge of ex­tinc­tion. (Zhang, et al., 2010)

• IUCN Red List

  Critically Endangered

• CITES

  Appendix I

Other Com­ments

It is im­por­tant to note that N. hainanus and most other gib­bon species are in the midst of con­tro­versy con­cern­ing their clas­si­fi­ca­tion. By the 1980s, Ma et al. re­ported that N. hainanus has been known as Hy­lo­bates hainanus, Hy­lo­bates pilea­tus, Hy­lo­bates con­color con­color and was then known as Hy­lo­bates con­color hainanus. Wei et al. noted that since the 1980s the species has been known as No­mas­cus con­color, No­mas­cus na­su­tus, and Hy­lo­bates (No­mas­cus) hainanus. Wei et al re­ferred to the species as No­mas­cus sp. cf. Na­su­tus hainanus. The species is now known as No­mas­cus hainanus based on mor­pho­log­i­cal, vocal, and ge­netic char­ac­ters. (Ma, et al., 1988; Moot­nick and Fan, 2011; Moot­nick, et al., 2012; Wei, et al., 2004)

There are cur­rently four gen­era of gib­bons; Hoolock, Hy­lo­bates, No­mas­cus, and Sym­pha­lan­gus. Each genus dif­fers in the num­ber of chro­mo­somes, with all six species of No­mas­cus hav­ing 52. Zihlman et al. be­lieve that the dis­tri­b­u­tion of body mass can also be used to clas­sify species into these gen­era. (Zihlman, et al., 2011)

Con­trib­u­tors

Rob Gre­goire (au­thor), Uni­ver­sity of Man­i­toba, Jane Wa­ter­man (ed­i­tor), Uni­ver­sity of Man­i­toba, Tanya Dewey (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

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