Animal Diversity Web

Di­ver­sity

Pongo spp con­sists of three species of orang­utan, the largest ar­bo­real species, and a mem­ber of the Great Apes. The first two ar­tic­u­lated species were P. abelii (Les­son 1827)(Suma­tran Orang­utan) and P. pyg­maeus (Lin­neus 1760) (Bornean Orang­utan) who were rec­og­nized as dis­tinct species since 2001 based on mi­to­chon­dr­ial DNA analy­sis. How­ever, a small south­ern pop­u­la­tion of the Suma­tran Orang­utan, pre­vi­ously thought of as P. abelii, was rec­og­nized as their own species in 2017 as P. tapan­ulien­sis (Tapan­uli orang­utan). This was due to a com­bi­na­tion of small mor­pho­log­i­cal dif­fer­ences like skull size, first molar size, hair tex­ture and ge­nomic di­ver­sity. The mor­pho­log­i­cal and be­ha­vo­r­ial dif­fer­ences be­tween P. abelii and P. pyg­maeus are more ap­par­ent, with Bornean orang­utans (P. pyg­maeus) com­ing to the ground less fre­quently than P. abelii and hav­ing more fatty flanges in the adult males. ("Mor­pho­me­t­ric, Be­hav­ioral, and Ge­nomic Ev­i­dence for a New Orang­utan Species", 2017; Xu and Ar­na­son, 1996)

Ge­o­graphic Range

All three species of genus Pongo are found in the Ori­en­tal Re­gion, specif­i­cally the is­lands of In­done­sia. P. abelii and P. tapan­ulien­sis are found in North­ern Suma­tra. P. pyg­maeus is found ex­clu­sively in Bor­neo, from the north­ern provinces of Sabah to Kali­man­tan. ("Bornean Orang­utan", 08 Feb­ru­ary 2016; "Suma­tran Orang­utan", 16 Oc­to­ber 2017; "Tapan­uli Orang­utan", 11 Oc­to­ber 2017)

• Biogeographic Regions
• indian ocean
  • native

Habi­tat

Mem­bers of Pongo spp. re­side mainly in trop­i­cal ever­green forests, but their high­est pop­u­la­tion den­si­ties occur in swamps, fer­tile val­leys, and low­land soils. Orang­utans pre­fer places with the most fer­tile soil, as this will yield the most fruit. Fruit trees in the Meli­acedae (ma­hogany) fam­ily rep­re­sent a com­mon fea­ture of many of their cho­sen habi­tats. Gen­er­ally, it is as­sumed that Bornean orang­utans have smaller ranges than those on Suma­tra, but this is not the case. Males typ­i­cally have larger ranges than fe­males, and both male and fe­male ranges will over­lap with other orang­utans. Range size is de­bated and varies from 850ha. to 2500ha, and per­haps even more.

Orang­utans also uti­lize dis­turbed and frag­mented forests, a trait that is price­less with the rapid de­te­ri­o­ra­tion of their old-growth habi­tat. They pre­fer areas of in­creased canopy clo­sure, ver­ti­cal sta­bil­ity, and uni­form height. Canopy lay­er­ing and shape was of lit­tle im­por­tance for se­lec­tion. Orang­utans in­hab­it­ing highly frag­mented areas are im­por­tant for con­nec­tiv­ity of metapop­u­la­tions and can still per­sist in these areas, like palm-oil forests.

There are vast areas of un­in­hab­ited trop­i­cal for­est in both Bor­neo and Suma­tra as well as swamps, and re­searchers think this could come from a vast array of rea­sons. Thou­sands of years of hunt­ing in com­bi­na­tion with oc­ca­sional droughts caus­ing star­va­tion could have con­tributed to the va­cancy in these now high-qual­ity habi­tats. (An­cre­naz, et al., 2021; Davies, et al., 2017; Payne and Pru­dente, 2008; Sea­man, et al., 2019)

• Habitat Regions
• tropical

• Terrestrial Biomes
• rainforest

• Wetlands
• swamp

Sys­tem­atic and Tax­o­nomic His­tory

Orang­utans are clas­si­fied as mem­bers of the pla­cen­tal mam­mals, or in­fr­a­class Eu­the­ria. They are mem­bers of fam­ily ho­minidae, or the fam­ily con­tain­ing Great Apes and Hu­mans. Great Apes in­clude bono­bos, east­ern and west­ern go­ril­las, chim­panzees, and the orang­utans.

In 2009, re­searchers found that at least 13 mil­lion years ago, hu­mans and orang­utans shared a com­mon an­ces­tor al­though species from genus Pongo are the least re­lated great ape to hu­mans.

Based on his­tor­i­cal bio­geo­graph­i­cal re­con­struc­tion, the an­ces­tral pop­u­la­tion of orang­utan most likely came from main­land Asia and set­tled on the North­ern end of Suma­tra. Within the Suma­tran pop­u­la­tion, re­cently a new species has been ar­tic­u­lated sep­a­rate from P. abelii. Ge­netic ev­i­dence in com­bi­na­tion with de­vel­op­men­tal dif­fer­ences in skull size dis­tin­guish P. tapan­ulien­sis as a species and thus, one of the most en­dan­gered species of Great Ape, with per­haps only 800 in­di­vid­u­als in ex­is­tence today. How­ever, P. tapan­ulien­sis is also the old­est species of orang­utan, di­verg­ing about 3.38 mil­lion years ago. About 674 thou­sand years ago, ge­netic mod­el­ing in­di­cates that the Suma­tran and Bornean pop­u­la­tions split. (Gre­han and Schwartz, 2009; "Mor­pho­me­t­ric, Be­hav­ioral, and Ge­nomic Ev­i­dence for a New Orang­utan Species", 2017; Xin, et al., 2013; Xu and Ar­na­son, 1996)

• Synonyms

  • Faunus (Oken, 1816)
  • Lophotus (Fischer, 1813)
  • Macrobates (Bilberg, 1828)
  • Satyrus (Lesson, 1840)

• Synapomorphies

  • Exclusively Arboreal (unless male is too large for branches)
  • Cheek Flanges in males

Phys­i­cal De­scrip­tion

Orang­utans are char­ac­ter­ized by their ape-like ap­pear­ance and dis­tinc­tive red, shaggy hair that cov­ers al­most their en­tire body, with males and some fe­male pos­sess­ing a beard of the same color. Their long arms, up to 7 or 8 feet in length, also char­ac­ter­ize this genus. Males weigh around 160 pounds with fe­males around 80. They have ex­tremely flex­i­ble joints with full ro­ta­tion of their hips. Both their long arms and flex­i­ble hips aid in their quadru­manous scram­bling, which dif­fers from swing­ing from branches, and fea­tures in­di­vid­u­als shift­ing their weight to force branches to bend over to the next branch. Their weight is also note­wor­thy, with males weigh­ing up­wards of 300 pounds and fe­males at 150.

Most his­toric lit­er­a­ture is cur­rently aimed at dis­tin­guish­ing phys­i­cal char­ac­ter­is­tics of the Bornean and Suma­tran pop­u­la­tions of orang­utan. There are gen­eral trends be­tween the two is­lands, with Suma­tran in­di­vid­u­als hav­ing a less broad of a face and being slightly lighter than Bornean Orang­utans. Per­haps the biggest dif­fer­ence in the two re­gional pop­u­la­tions is the shape and tex­ture of the male cheek flanges (pads). Male orang­utans pos­sess cheek flaps later in de­vel­op­ment as a form of sex­ual se­lec­tion, with big­ger flanges in­di­cat­ing a more suc­cess­ful mate. Suma­tran males are noted to have a di­a­mond like shape of their flanges, with tufts of short yel­low or white hair. Bornean coun­ter­parts have a more square shape of the flanges, de­vel­op­ing more lat­er­ally and rounded. It has few hairs and wrin­kles the brow and creases the nose, giv­ing Bornean males a mostly grumpy ap­pear­ance. (Abrams, 2017; Mack­in­non, 1975)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Re­pro­duc­tion

Orang­utans are known for hav­ing the slow­est life his­tory of not only all great apes, but mam­mals in gen­eral. It takes an av­er­age of 15.4 years for a fe­male to be­come re­pro­duc­tively ac­tive, with a range of 13-18 years. Fe­males, on av­er­age, birth young about every 9 years.

Fe­males that are re­pro­duc­tively ac­tive are usu­ally trav­el­ing alone or with their off­spring. If there is a male and a fe­male trav­el­ing to­gether, it may be due to a sex­ual re­la­tion­ship or a co­in­ci­den­tal close­ness in prox­im­ity from feed­ing. Males, flanged or un­flanged, pur­sue fe­males that are re­pro­duc­tively re­cep­tive, and will fight for a re­pro­duc­tively ac­tive fe­male. Flanged males have cheek pads and longer vo­cal­iza­tions, as well as usu­ally being more dom­i­nant and sex­u­ally suc­cess­ful. How­ever, they are ex­tremely in­tol­er­ant of other males, using their vo­cal­iza­tions from throat pouches as a way to alert other males of their pres­ence.

The bi­ma­tur­ism of male orang­utans have im­pli­ca­tions on their court­ing be­hav­ior for a fe­male. As noted, flanged males use pri­mar­ily their vo­cal­iza­tions that deter males and at­tract a fe­male. Un­flanged males re­sort to search­ing for a fe­male.

Fe­male choice is the main fac­tor in mat­ing suc­cess. Older fe­males pre­fer more flanged, dom­i­nant males. Some­times, forced mat­ing oc­curs, and this is ac­com­pa­nied by re­sis­tance and/or a fight. Fe­males can be co­op­er­a­tive at the be­gin­ning and re­sis­tant to­wards the end or vice versa.

Once the fe­male is re­cep­tive to re­pro­duc­tion, an in­vol­un­tary con­sortship is formed for any­where from a few days to a month. Dur­ing this time, the male and fe­male travel to­gether, and both flanged and un­flanged males ex­hibit mate guard­ing be­hav­ior to keep other males away. How­ever, usu­ally more dom­i­nant, flanged males are more suc­cess­ful in mate guard­ing, while un­flanged males being kicked out by a larger male if en­coun­tered. (Payne and Pru­dente, 2008; Shu­maker, et al., 2008; S.S, et al., 2009)

• Mating System
• polyandrous

Once im­preg­nated, ges­ta­tion for fe­male orang­utans lasts about 8 and a half months. There is no breed­ing sea­son for this genus, and fe­males are able to have off­spring year-round up until they die. As stated pre­vi­ously, fe­males have off­spring about every 9 years al­most al­ways to one, with very rarely hav­ing twins.

New­born orang­utans are ex­tremely de­pen­dent upon their mother, and weigh 3.5-4.5 pounds. Body con­tact is con­tin­u­ous for the first 3 months, but en­tire de­pen­dence on food lasts for the first two years. At around 3 years of age, young orang­utans make play nests and start ex­plor­ing their habi­tat while al­ways in view of the mother.

Full wean­ing of milk does not occur until about 3.5 years old. Young orang­utans will spend the next few years im­i­tat­ing their mother's be­hav­ior through trial and error. The mother will teach her young every­thing from swing­ing through trees, using tools for food, and over­all how to live in the for­est.

At about six or seven years of age, off­spring are con­sid­ered ado­les­cents and spend more and more time away from their mother. At this age, fe­males ex­press an in­ter­est in sex­ual se­lec­tion and can be re­pro­duc­tively ac­tive, al­though males tend to pur­sue older, more es­tab­lished fe­males. Fe­males may not give birth until they are 10-15 years of age. Nei­ther males or fe­males are fully grown at this age, and will oc­ca­sion­ally come into con­tact with their mother dur­ing this pe­riod. Their mother may have given birth to a sib­ling by then, giv­ing these ado­les­cents some­one to play with. Males will not re­pro­duce until they are 13-15 years old, de­spite being re­pro­duc­tively fer­tile well be­fore that. (Payne and Pru­dente, 2008; Shu­maker, et al., 2008; S.S, et al., 2009)

• Key Reproductive Features
• year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

Orang­utans are semi-soli­tary in na­ture, so males have al­most no in­vest­ment or care into off­spring.

Fe­males de­velop a strong bond with their young, and tim­ing and in­vest­ment are stated in the pre­vi­ous sec­tion. When she gives birth to a new­born, she often shields it from view. A wild fe­male orang­utan may only have 3-5 off­spring in her en­tire life. (Payne and Pru­dente, 2008; Shu­maker, et al., 2008; S.S, et al., 2009)

• Parental Investment
• altricial
• female parental care
• pre-fertilization
  • protecting
    • male
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• extended period of juvenile learning

Lifes­pan/Longevity

Orang­utans are fairly long-lived apes in the wild liv­ing up to 58 years for males and 53 for fe­males. In cap­tiv­ity, they are known to live as long, but the old­est cap­tive orang­utan is thought to have been 61 when she died.

Orang­utans most com­monly die of old age in the wild, but cur­rent hu­man-in­duced threats in­clude star­va­tion, hunt­ing by hu­mans as pests, cap­tur­ing ba­bies to be sold on the black mar­ket as pests, and wild­fires. (Tacutu, et al., 2017)

Be­hav­ior

As stated be­fore, mem­bers of the genus pongo are semi-soli­tary for most of their adult life. They are motile, and their day-to-day move­ments are largely a re­sponse to spa­tiotem­po­ral vari­abil­ity in food avail­abil­ity. They eat mainly ripe fruits and food dis­tri­b­u­tion is vari­able, so most orang­utans travel alone un­less it is a fe­male with her off­spring. Adult flanged males are the most in­tol­er­ant of other mem­bers of their species un­less they are ac­tively try­ing to form a con­sortship with an­other fe­male, thus they are rarely ter­ri­to­r­ial. Be­sides when mat­ing, orang­utans are tol­er­ant of other mem­bers of their species in their home range, how­ever males tend to stay away from each other more than fe­males. They are motile, and their day-to-day move­ments are largely a re­sponse to spa­tiotem­po­ral vari­abil­ity in food avail­abil­ity.

There is a so­cial hi­er­ar­chy, but flanged males are at the top. They can out­com­pete un­flanged males for a mate and will typ­i­cally choose an older fe­male rather than an ado­les­cent one.

Their lo­co­mo­tion through the trees is a dis­tin­guish­ing char­ac­ter­is­tic of these Great Apes. They climb, clamor, and brachi­ate through the canopy, in­gest­ing over 90% of their diet in this re­gion.

Tool use also de­fines orang­utans. Most stud­ies have fo­cused on the be­hav­ioral dif­fer­ences be­tween the two re­gional pop­u­la­tions of orang­utans, or Bornean and Suma­tran Is­land pop­u­la­tions. Most orang­utan off­spring learn all of their be­hav­iors from their mother, in­clud­ing tool use. In­ter­est­ingly, re­search has found that dif­fer­ent pop­u­la­tions of orang­utan dis­play dif­fer­ent be­hav­iors based off of their ge­o­graphic re­gion, an in­di­ca­tion of a cul­ture. Roof build­ing of nests (to stop rain) was ob­served in Bor­neo, but not on Suma­tra. There were other be­hav­iors, like cov­er­ing your­self in leaves to pro­tect from the sun, that were ob­served in some of the pop­u­la­tions on Bor­neo and Suma­tra, but not all.

Orang­utans on the is­land Suma­tra have gen­er­ally been ob­served using tools more than that of Bor­neo. These orang­utans are known to use sticks to poke out in­sects from trees and leaves to hold fruits with spines, as well as many oth­ers. Bornean orang­utans are gen­er­ally more so­cial, and thus in cap­tiv­ity, have learned a va­ri­ety of be­hav­iors from orang­utans and hu­mans that are ob­vi­ously not their species or di­rect mother. They have been known to make paint­ings in cap­tiv­ity as well as learn sign lan­guage, or as­so­ci­ate spe­cific signs with spe­cific human mean­ings. Re­ha­bil­i­tat­ing orang­utans in Tan­jung Na­tional Park in Kali­man­tan were seen im­i­tat­ing human be­hav­ior like clothes wash­ing, teeth brush­ing, ham­mer­ing nails, and vol­un­tar­ily rid­ing in boats. (Payne and Pru­dente, 2008; Schaik, et al., 2008)

• Key Behaviors
• arboreal
• scansorial
• diurnal
• motile
• solitary
• dominance hierarchies

Com­mu­ni­ca­tion and Per­cep­tion

Com­mu­ni­ca­tion among mem­bers of genus Pongo is per­haps one of the most com­plex and di­verse char­ac­ter­is­tics of these an­i­mals. The most dis­tinct and charis­matic form of com­mu­ni­ca­tion for orang­utans is the "long call," per­formed by adult flanged males only. Heard from over a mile away, these long calls in­vite be­hav­ioral re­sponses from all ages and sexes, but other adult males re­spond the most. The flanged male uses their throat sac to emit a long, some­times min­utes long, se­ries of "roars." Their cheek pads fun­nel the sound in a par­tic­u­lar di­rec­tion, and stud­ies have shown males will some­times make these calls in the di­rec­tion they are trav­el­ing to warn other males they are on the move to­wards them as early as one day in ad­vance. Other males use their long calls in re­sponse to trees falling, mostly be­cause some males will knock down trees as a form of dom­i­nance. Some males use their long calls to at­tract fe­males, and it has been noted that Bornean fe­male orang­utans can rec­og­nize the calls of in­di­vid­ual males.

Be­sides long calls, there are many other forms of orang­utan vocal com­mu­ni­ca­tion. Bornean orang­utans were ob­served in 2019 to have 11 vocal sig­nal types. These vocal sig­nals can be any­thing from dis­plea­sure, to play­ful in­fants fight­ing, to warn­ing of rain­fall. In fact, Suma­tran orang­utans were ob­served sup­press­ing alarm calls up to 20 min­utes when wait­ing for threats to pass. This means they are ca­pa­ble time-space-dis­placed re­sponses or giv­ing in­for­ma­tion about an event that has hap­pened in the past.

Ges­tures are per­haps the most widely-used orang­utan form of com­mu­ni­ca­tions. Over 21 ges­ture types were iden­ti­fied in a Bornean pop­u­la­tion of orang­utans in 2019. They have a range of mean­ings, from re­quest­ing ob­jects, shar­ing tools, warn­ing of harm­ful be­hav­ior, climb over/on me, re­sume play, etc. Ges­tures can be made by hands or feet, though hands are pre­ferred. Orang­utans have also been known to re­peat ges­tures when their mes­sage was only par­tially un­der­stood, and in some cases can change their ges­tures if they be­lieve their mes­sage was not un­der­stood at all. (Cart­mill and Byrne, 2010; Galdikas and In­s­ley, 1988; Lameira and Call, 2018; Leav­ens, 2007; Payne and Pru­dente, 2008)

• Communication Channels
• visual
• acoustic

• Other Communication Modes
• mimicry

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Orang­utans are highly op­por­tunis­tic for­agers, with over 317 food sources noted in 1988 with a com­plete species list num­ber­ing over 1600 dif­fer­ent species preyed upon by orang­utans. When re­sources are abun­dant, they pre­fer to con­sume fruits as 60% of the orang­utan diet is fruit, but this varies month to month. When fruit is avail­able, they con­sume a plethora of dif­fer­ent species like ficus and durian, the bulk of their diet, but they will eat ap­ples, or­anges, ba­nanas, berries, ly­chees, bread­fruit, and jack­fruit. With de­creas­ing habi­tat avail­able, many orang­utans are raid­ing farm­ers fruit crops, with fe­males being more likely to raid than males. In ad­di­tion, it's been found that the great­est fac­tor to their dis­tri­b­u­tion, which is linked to for­ag­ing, is rest­ing time. While much of their time is spent for­ag­ing, the pe­ri­ods of rest in be­tween are the main de­ter­mi­nant of dis­tri­b­u­tion.

When fruit isn't an op­tion, many orang­utans will in­crease from 22% of their for­ag­ing time for bark to 44%. In ad­di­tion to tree bark, species like Giron­niera ner­vosa are also an im­por­tant source of leaves and flow­ers. Most mem­bers of pongo pre­fer younger leaves and flow­ers, as many adult leaves de­velop tox­ins that can be harm­ful for her­bi­vores. They also con­sume nec­tar and honey from trees and plants.

Orang­utans don't only eat plants, con­sum­ing in­ver­te­brate species in­clude 4 species of ants, 4 species of ter­mites, 2 species of cater­pil­lars, leeches, mag­gots, ticks, and lar­vae. They poke out many of these in­ver­te­brates using a stick in the bur­rows or crevices where the in­ver­te­brates re­side. Orang­tu­ans will also eat ver­te­brates in­clud­ing the eggs of many bird species, tree rats, small lizards, and pri­mates like loras or gib­bons.

There are a few re­gional dif­fer­ences be­tween the orang­utan diet. Sub­pop­u­la­tions of orang­utans each vary widely on what they eat, as their for­ag­ing be­hav­ior de­ter­mines what they eat, and their be­hav­ior varies by pop­u­la­tion. For ex­am­ple, on the is­land of Suma­tra, figs are much more preva­lent, so Suma­tran orang­utans have a higher fig den­sity in their diet. (Camp­bell-Smith and Camp­bell-Smith, 2011; Carne, et al., 2015; Galdikas and In­s­ley, 1988; Rus­son, et al., 2009)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates
  • insectivore
• herbivore
  • folivore
  • frugivore
  • granivore
  • lignivore
  • nectarivore
• omnivore

Pre­da­tion

There are few preda­tors for mem­bers of genus pongo be­sides hu­mans. Tigers and leop­ards are the main preda­tor of orang­utan, but it is very rare as most of these preda­tors have been ex­tir­pated from their orig­i­nal home ranges. Young orang­utans are at most risk of pre­da­tion, but being ar­bo­real, orang­utans are rarely pre­dated upon. Bornean orang­utans do not have to worry about tigers, as they have been erad­i­cated from the is­land for decades. If a preda­tor is spot­ted, many orang­utans will raise an alarm call for neigh­bor­ing orang­utans, often after the preda­tor has passed. (Lameira and Call, 2018; Schaik, et al., 2008)

• Known Predators

  • Leopard
  • Tiger

Ecosys­tem Roles

With hun­dreds of plant and tree species pre­dated upon by the genus g. pongo, orang­utans are im­por­tant seed dis­persers for the forests they re­side in. These forests house many other spec­tac­u­lar and rare species, like the Suma­tran tiger or Suma­tran ele­phant. (Galdikas, 1988)

• Ecosystem Impact
• disperses seeds
• creates habitat

Con­ser­va­tion Sta­tus

All 3 species in this genus are con­sid­ered crit­i­cally en­dan­gered by the IUCN. Pro­jec­tions aren't up to date but es­ti­mate around 102,000 Bornean orang­utans, 13,800 Suma­tran orang­utans, and fewer than 800 Tapan­uli orang­utans. All major threats to mem­bers of pongo* are hu­man-in­duced or hu­man-re­lated, with the largest of these threats is habi­tat loss. Con­ver­sion of for­est to agri­cul­ture is the main form of habi­tat loss, with the Suma­tran orang­utan being heav­ily af­fected by palm-oil plan­ta­tions. Leg­is­la­tion like the Aceh Provin­cial Spa­tial Plan of 2013 dis­re­gards Suma­tran orang­utan habi­tat in favor of ex­pan­sion of palm oil plan­ta­tions into their ter­ri­tory. Hous­ing, tourism, and recre­ation de­vel­op­ment also threaten orang­utan habi­tat. Log­ging for tim­ber, cre­ation of roads, and min­ing op­er­a­tions all con­tribute to habi­tat frag­men­ta­tion. Orang­utans are also sub­ject to the il­le­gal pet trade, with in­ten­tional killing of adult fe­male orang­utans and the sell­ing of her or­phans on the black mar­ket. Fires on Bor­neo af­fect the Tapan­uli and Bornean orang­utans, like when 90% of Kutai Na­tional Park was burned and killed thou­sands of orang­utans in the process.

Con­ser­va­tion Ac­tion is cur­rently lack­ing for orang­utans. There is no sys­tem­atic mon­i­tor­ing scheme for any species of orang­utan. There are ac­tion re­cov­ery plans for all but the species P. pyg­maeus, or the Bornean Orang­utan. Con­ser­va­tion sites have been iden­ti­fied for all 3 species of orang­utan, but P. pyg­maeus is lack­ing sites over their en­tire range. While over 90% of the Suma­tran pop­u­la­tion is pro­tected, a mere 35% is pro­tected for Bornean species, and only 1-10% for the Tapan­uli orang­utan. How­ever, there is hope, as all species have been in­cluded in in­ter­na­tional leg­is­la­tion and are sub­ject to in­ter­na­tional trade con­trol. There have also been re­cent ed­u­ca­tion and aware­ness pro­grams for all 3 species. ("IUCN Red List", 16 Oc­to­ber 2017; "IUCN Red List", Feb­ru­ary 8 2016; "IUCN Red List", Oc­to­ber 11 2017)

• IUCN Red List [Link]

  Not Evaluated

Con­trib­u­tors

Alexan­der Hey (au­thor), Col­orado State Uni­ver­sity, Tanya Dewey (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

08 Feb­ru­ary 2016. "Bornean Orang­utan" (On-line). IUCN Red List. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​iucnredlist.​org/​species/​17975/​123809220.

Feb­ru­ary 8 2016. "IUCN Red List" (On-line). Bornean Orang­utan. Ac­cessed Oc­to­ber 27, 2021 at https://​www.​iucnredlist.​org/​species/​17975/​123809220.

16 Oc­to­ber 2017. "IUCN Red List" (On-line). Suma­tran Orang­utan. Ac­cessed Oc­to­ber 27, 2021 at https://​www.​iucnredlist.​org/​species/​121097935/​123797627.

Oc­to­ber 11 2017. "IUCN Red List" (On-line). Tapan­uli Orang­utan. Ac­cessed Oc­to­ber 27, 2021 at https://​www.​iucnredlist.​org/​species/​120588639/​120588662.

2017. Mor­pho­me­t­ric, Be­hav­ioral, and Ge­nomic Ev­i­dence for a New Orang­utan Species. Cur­rent Bi­ol­ogy, 27: 3487-3498.e10. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​sciencedirect.​com/​science/​article/​pii/​S0960982217312459.

16 Oc­to­ber 2017. "Suma­tran Orang­utan" (On-line). IUCN Red List. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​iucnredlist.​org/​species/​121097935/​123797627.

11 Oc­to­ber 2017. "Tapan­uli Orang­utan" (On-line). IUCN Red List. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​iucnredlist.​org/​species/​120588639/​120588662.

Abrams, S. 2017. "New Eng­land Pri­mate Con­ser­vancy" (On-line). Suma­tran Orang­utan. Ac­cessed Sep­tem­ber 29, 2021 at https://​www.​neprimateconservancy.​org/​sumatran-orangutan.​html.

An­cre­naz, M., F. Oram, N. Nardiy­ono, M. Slimi. 2021. Im­por­tance of Small For­est Frag­ments in Agri­cul­tural Land­scapes for Main­tain­ing Orang­utan Metapop­u­la­tions. Fron­tiers in Forests and Global Change, 4: 5. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​frontiersin.​org/​articles/​10.​3389/​ffgc.​2021.​560944/​full.

Camp­bell-Smith, G., M. Camp­bell-Smith. 2011. Raiders of the Lost Bark: Orang­utan For­ag­ing Strate­gies in a De­graded Land­scape. PLoS ONE, Vol­ume 6, Issue 6: e20962. Ac­cessed Oc­to­ber 20, 2021 at https://​www.​ncbi.​nlm.​nih.​gov/​pmc/​articles/​PMC3120831/​.

Carne, C., S. Sem­ple, J. Lehmann. 2015. In­ves­ti­gat­ing Con­straints on the Sur­vival of Orang­utans Across Bor­neo and Suma­tra. Trop­i­cal Con­ser­va­tion Sci­ence, Vol­ume 8, Issue 4: 940-954. Ac­cessed Oc­to­ber 20, 2021 at https://​doi.​org/​10.​1177/​194008291500800405.

Cart­mill, E., R. Byrne. 2010. Se­man­tics of pri­mate ges­tures: in­ten­tional mean­ings of orang­utan ges­tures. An­i­mal Cog­ni­tion, 13/6: 793-804. Ac­cessed Oc­to­ber 13, 2021 at 10.1007/s10071-010-0328-7.

Davies, A., M. An­cre­naz, F. Oram, G. Asner. 2017. Canopy struc­ture dri­ves orang­utan habi­tat se­lec­tion in dis­turbed Bornean forests. Pro­ceed­ings of the Na­tional Acad­emy of Sci­ences, 114: 8307-8312. Ac­cessed Sep­tem­ber 15, 2021 at https://​www.​pnas.​org/​content/​114/​31/​8307.

Galdikas, B. 1988. Orang­utan diet, range, and ac­tiv­ity at Tan­jung Put­ing, Cen­tral Bor­neo. In­ter­na­tional Jour­nal of Pri­ma­tol­ogy, Vol­ume 9, Issue 1: 1-35. Ac­cessed Oc­to­ber 20, 2021 at https://​doi.​org/​10.​1007/​BF02740195.

Galdikas, B., S. In­s­ley. 1988. The Fast Call of the Adult Male Orang­utan. Jour­nal of Mam­mal­ogy, 69/2: 371-375. Ac­cessed Oc­to­ber 13, 2021 at https://​www.​jstor.​org/​stable/​1381390.

Gre­han, J., J. Schwartz. 2009. Evo­lu­tion of the sec­ond orang­utan: phy­logeny and bio­geog­ra­phy of ho­minid ori­gins. Jour­nal of Bio­geog­ra­phy, 36: 1823-1844.

Lameira, A., J. Call. 2018. Time-space–dis­placed re­sponses in the orang­utan vocal sys­tem. Sci­ence Ad­vances, 4/11. Ac­cessed Oc­to­ber 13, 2021 at https://​www.​science.​org/​doi/​10.​1126/​sciadv.​aau3401.

Leav­ens, D. 2007. An­i­mal Cog­ni­tion: Mul­ti­modal Tac­tics of Orang­utan Com­mu­ni­ca­tion. Cur­rent Bi­ol­ogy, 17: R762-R764. Ac­cessed Oc­to­ber 13, 2021 at https://​www.​sciencedirect.​com/​science/​article/​pii/​S0960982207016880.

Mack­in­non, J. 1975. Dis­tin­guish­ing char­ac­ters of the in­su­lar forms of orang-utan. In­ter­na­tional Zoo Year­book, 15: 195-197. Ac­cessed Sep­tem­ber 29, 2021 at https://​onlinelibrary.​wiley.​com/​doi/​abs/​10.​1111/​j.​1748-1090.​1975.​tb01398.​x.

Payne, J., C. Pru­dente. 2008. Orang­utans: Be­hav­ior, Ecol­ogy, and Con­ser­va­tion. North Amer­ica: The MIT Press.

Rus­son, A., S. Wich, M. An­cre­naz, T. Kanamori, C. Knott. 2009. Ge­o­graphic vari­a­tion in orang­utan diets. Orang­utans: ge­o­graphic vari­a­tion in be­hav­ioral ecol­ogy and con­ser­va­tion: 135-156. Ac­cessed Oc­to­ber 20, 2021 at https://​www.​zora.​uzh.​ch/​id/​eprint/​31255/​.

S.S, U., T. Setia, B. Goossens, J. S, C. Knott. 2009. Orang­utan mat­ing be­hav­ior and strate­gies. Orang­utans: Ge­o­graphic Vari­a­tion in Be­hav­ioral Ecol­ogy and Con­ser­va­tion, 1: 235-244. Ac­cessed Oc­to­ber 06, 2021 at https://​www.​researchgate.​net/​publication/​230823426_​Orangutan_​mating_​behavior_​and_​strategies.

Schaik, C., A. Mar­shall, S. Wich. 2008. Ge­o­graphic vari­a­tion in orang­utan be­hav­ior and bi­ol­ogy. Orang­utans: 351-361. Ac­cessed Oc­to­ber 13, 2021 at https://​oxford.​universitypressscholarship.​com/​view/​10.​1093/​acprof:​oso/​9780199213276.​001.​0001/​acprof-9780199213276-chapter-24.

Sea­man, D., H. Bernard, M. An­cre­naz, D. Coomes. 2019. Den­si­ties of Bornean orang‐utans (Pongo pyg­maeus morio) in heav­ily de­graded for­est and oil palm plan­ta­tions in Sabah, Bor­neo. Amer­i­can jour­nal of pri­ma­tol­ogy, 81: e23030–n/a.

Shu­maker, R., S. Wich, L. Perkins. 2008. Re­pro­duc­tive Life His­tory Traits of Fe­male Orang­utans (Pongo spp.). Pri­mate Re­pro­duc­tive Aging, 36: 147-161. Ac­cessed Oc­to­ber 06, 2021 at https://​www.​karger.​com/​Article/​FullText/​137705.

Tacutu, R., D. Thorn­ton, E. John­son, A. Bu­dovsky, D. Barado, T. Craig, E. Diana, G. Lehmann, D. Toren, J. Wang. 2017. "Human Age­ing and Ge­nomic Re­sources" (On-line). AnAge entry for Pongo pyg­maeus. Ac­cessed Sep­tem­ber 30, 2021 at https://​genomics.​senescence.​info/​legal.​html#​citation.

Xin, M., J. Kel­ley, K. Eil­ert­son, S. Musharoff, J. De­gen­hardt. 2013. Pop­u­la­tion Ge­nomic Analy­sis Re­veals a Rich Spe­ci­a­tion and De­mo­graphic His­tory of Orang-utans (Pongo pyg­maeus and Pongo abelii). PLOS ONE, 10: e77175. Ac­cessed Sep­tem­ber 22, 2021 at https://​journals.​plos.​org/​plosone/​article?​id=10.​1371/​journal.​pone.​0077175.

Xu, X., U. Ar­na­son. 1996. The mi­to­chon­dr­ial DNA mol­e­cule of Suma­tran orang­utan and a mol­e­c­u­lar pro­posal for two (Bornean and Suma­tran) species of orang­utan. Jour­nal of Mol­e­c­u­lar Evo­lu­tion, 43: 431-437. Ac­cessed Sep­tem­ber 15, 2021 at https://​pubmed.​ncbi.​nlm.​nih.​gov/​8875856/​.