Editing Orangutan (section)

=== Reproduction and development ===

{{multiple image
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 | image1 = Male Bornean Orangutan - Big Cheeks.jpg
 | image2 = Here's Looking At You, Kid (5656539778).jpg
 | caption1 = Flanged male orangutan
 | alt caption1= Male orangutan exhibiting the facial flange and throat pouch
 | caption2 = Unflanged male orangutan
 |alt caption2 = A male orangutan with no facial flange or throat pouch
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Males become sexually mature at around age 15. They may exhibit [[Neoteny|arrested development]] by not developing the distinctive cheek pads, pronounced throat pouches, long fur, or long calls until a resident dominant male is absent. The transformation from unflanged to flanged can occur quickly. Flanged males attract females in [[oestrous]] with their characteristic long calls, which may also suppress development in younger males.<ref name="Utami 2002">{{cite journal | last1 = Utami | first1 = S. S. | last2 = Goossens | first2 = B. | last3 = Bruford | first3 = M. W. | last4 = de Ruiter | first4 = J. R. | last5 = van Hooff | first5 = J. A. R. A. M. | author-link5 = Jan van Hooff | year = 2002 | title = Male bimaturism and reproductive success in Sumatran orangutans | journal = Behavioral Ecology | volume = 13 | issue = 5| pages = 643–52 | doi = 10.1093/beheco/13.5.643| doi-access = free }}</ref><ref name=Payne/>{{rp|100}}

Unflanged males wander widely in search of oestrous females and upon finding one, may [[Sexual coercion among animals|force copulation]] on her, the occurrence of which is unusually high among mammals. Females prefer to mate with the fitter flanged males, forming pairs with them and benefiting from their protection.<ref name="Fox 2002">{{cite journal | last1 = Fox | first1 = E. A. | year = 2002 | title = Female tactics to reduce sexual harassment in the Sumatran orangutan (''Pongo pygmaeus abelii'') | journal = [[Behavioral Ecology and Sociobiology]] | volume = 52 | issue = 2| pages = 93–101 | doi = 10.1007/s00265-002-0495-x| s2cid = 13583879 }}</ref><ref name="Delgrado 2000" /><ref name=Knott2009>{{cite journal|last1=Knott|first1=Cheryl Denise|last2=Thompson|first2=Melissa Emery|last3=Stumpf|first3=Rebecca M|last4=McIntyre|first4=Matthew H|year=2009|title=Female reproductive strategies in orangutans, evidence for female choice and counterstrategies to infanticide in a species with frequent sexual coercion|journal=Proceedings of the Royal Society B: Biological Sciences|volume=277|issue=1678|pages=105–13|doi=10.1098/rspb.2009.1552|pmid=19812079|pmc=2842634|doi-access=free}}</ref> Non-[[ovulation|ovulating]] females do not usually resist copulation with unflanged males, as the chance of conception is low.<ref name=Knott2009/> [[Homosexual behavior in animals|Homosexual behaviour]] has been recorded in the context of both affiliative and aggressive interactions.<ref>{{cite journal|last=Fox|first=Elizabeth A|year=2001|title=Homosexual behavior in wild Sumatran orangutans (''Pongo pygmaeus abelii'')|journal=American Journal of Primatology|volume=55|issue=3|pages=177–81|doi=10.1002/ajp.1051|pmid=11746281|s2cid=21561581}}</ref>
[[File:Bukit Lawang, orangutans (6785217748).jpg|thumb|left|upright|alt=A mother orangutan with her offspring|Mother orangutan with young]]
Unlike females of other non-human great ape species, orangutans do not exhibit [[sexual swelling]]s to signal fertility.<ref name=Knott2009/> A female first gives birth around 15 years of age and they have a six- to nine-year interbirth interval, the longest among the great apes.<ref name=Wich>{{cite book|last1=Wich |first1=Serge A. |author2=de Vries, Hans |author3=Ancrenaz, Marc |author4=Perkins, Lori |author5=Shumaker, Robert W. |author6=Suzuki, Akira| author7=van Schaik, Carel P. |contribution=Orangutan life history variation|editor1-first=Serge A. |editor1-last=Wich |editor2-first=S. Suci Utami |editor2-last=Atmoko |editor3-first=Tatang Mitra |editor3-last=Setia |editor4-last=van Schaik|editor4-first=Carel P. |title=Orangutans: Geographic Variation in Behavioral Ecology and Conservation|year=2009|url=https://archive.org/details/orangutansgeogra00wich|url-access=registration|publisher=Oxford University Press|pages=67–68|isbn=978-0199213276}}</ref> Gestation is around nine months long and infants are born at a weight of {{convert|1.5|–|2|kg|lb|abbr=on}}.<ref name=Payne/>{{rp|99}} Usually only a single infant is born; twins are a rare occurrence.<ref>{{cite journal|last1=Goossens|first1=B|last2=Mohd|first2=D|last3=Kapar|last4=Kahar|first4=S|year=2011|title=First Sighting of Bornean Orangutan Twins in the Wild|journal=Asian Primates Journal|volume=2|issue=1|pages=10–12|url=https://www.researchgate.net/publication/245023318}}</ref> Unlike many other primates, male orangutans do not seem to practise [[Infanticide (zoology)|infanticide]]. This may be because they cannot ensure they will sire a female's next offspring, because she does not immediately begin ovulating again after her infant dies.<ref>{{cite journal |last1=Beaudrot |first1=LH |last2=Kahlenberg |first2=SM |last3=Marshall |first3=AJ |year=2009 |title=Why male orangutans do not kill infants |journal=Behavioral Ecology and Sociobiology |volume=63 |issue=11 |pages=1549–62 |pmid=19701484 |pmc=2728907 |doi=10.1007/s00265-009-0827-1}}</ref> There is evidence that females with offspring under six years old generally avoid adult males.<ref>{{cite journal|last1=Scott|first1=A. M.|last2=Knott|first2=C. D.|last3=Susanto|first3=T. W.|year=2019|title=Are Male Orangutans a Threat to Infants? Evidence of Mother–Offspring Counterstrategies to Infanticide in Bornean Orangutans (''Pongo pygmaeus wurmbii'')|journal=International Journal of Primatology|volume=44|issue=3|pages=435–55|doi=10.1007/s10764-019-00097-8|hdl=2144/39274|s2cid=198190605|hdl-access=free}}</ref>

Females do most of the caring of the young. The mother will carry the infant while travelling, suckle it and sleep with it.<ref name=Payne/>{{rp|100}} During its first four months, the infant is almost never without physical contact and clings to its mother's belly. In the following months, the amount of physical contact the infant has with its mother declines. When an orangutan reaches the age of one-and-a-half years, its climbing skills improve and it will travel through the canopy holding hands with other orangutans, a behaviour known as "buddy travel".<ref name="Munn 1997">{{cite book |last1=Munn|first1= C. |last2=Fernandez|first2= M.|year=1997|contribution=Infant development |title=Orangutan Species Survival Plan Husbandry Manual |editor-first=Carol |editor-last=Sodaro |publisher=[[Chicago Zoological Park]] |pages=59–66 |oclc=40349739}}</ref> After two years of age, juvenile orangutans will begin to move away from their mothers temporarily. They reach adolescence at six or seven years of age and are able to live alone but retain some connections with their mothers.<ref name=Payne/>{{rp|100}} Females may nurse their offspring for up to eight years, which is more than any other mammal.<ref>{{cite journal|last1=Smith|first1=Tanya M.|last2=Austin|first2=Christine|last3=Hinde|first3=Katie|last4=Vogel|first4=Erin R.|last5=Arora|first5=Manish|year=2017|title=Cyclical nursing patterns in wild orangutans|journal=Evolutionary Biology|volume=3|issue=5|page=e1601517|doi=10.1126/sciadv.1601517|pmid=28560319|pmc=5435413|bibcode=2017SciA....3E1517S|doi-access=free}}</ref> Typically, orangutans live over 30 years both in the wild and in captivity.<ref name=Payne />{{rp|15}}
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