Cheyne, S. M.; Thompson, C. J.; Phillips, A. C.; Hill, R. M.; Limin, S. H. (2007). "Density and population estimate of gibbons (Hylobates albibarbis) in the Sabangau catchment, Central Kalimantan, Indonesia". Primates. 49 (1): 50–56. doi: 10.1007/s10329-007-0063-0. PMID 17899314. S2CID 1792717.

Wich, S. A.; Swartz, K. B.; Hardus, M. E.; Lameira, A. R.; Stromberg, E.; Shumaker, R. W. (2008). "A case of spontaneous acquisition of a human sound by an orangutan". Primates. 50 (1): 56–64. doi: 10.1007/s10329-008-0117-y. PMID 19052691. S2CID 708682. Orangutans may be killed for the bushmeat trade [122] and bones are secretly sold in souvenir shops in several cities in Indonesian Borneo. [123] Conflicts between locals and orangutans also pose a threat. Orangutans that have lost their homes often raid agricultural areas and end up being killed by villagers. [124] Locals may also be motivated to kill orangutans for food or because of their perceived danger. [125] Mother orangutans are killed so their infants can be sold as pets. Between 2012 and 2017, the Indonesian authorities, with the aid of the Orangutan Information Center, seized 114 orangutans, 39 of which were pets. [126]Singer, P. (18 July 2008). "Of great apes and men". The Guardian. Archived from the original on 13 November 2012 . Retrieved 10 November 2008. Wich, S A; Meijaard, E; Marshall, A J; Husson, S; etal. (2002). "Distribution and conservation status of the orang-utan ( Pongo spp.) on Borneo and Sumatra: how many remain?". Oryx. 42 (3): 329–39. doi: 10.5167/uzh-3914. Bower, B. (18 April 2011). "Orangutans use simple tools to catch fish". Wired. Archived from the original on 8 July 2013 . Retrieved 5 August 2013.

van Schaik, Carel P.; Damerius, L.; Isler, K. (2013). "Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance". PLoS One. 8 (9): e74896. Bibcode: 2013PLoSO...874896V. doi: 10.1371/journal.pone.0074896. PMC 3770631. PMID 24040357. Scott, A. M.; Knott, C. D.; Susanto, T. W. (2019). "Are Male Orangutans a Threat to Infants? Evidence of Mother–Offspring Counterstrategies to Infanticide in Bornean Orangutans ( Pongo pygmaeus wurmbii)". International Journal of Primatology. 44 (3): 435–55. doi: 10.1007/s10764-019-00097-8. hdl: 2144/39274. S2CID 198190605. In Western sources, the first printed attestation of the word for the apes is in Dutch physician Jacobus Bontius' 1631 Historiae naturalis et medicae Indiae orientalis. He reported that Malays had informed him the ape could talk, but preferred not to "lest he be compelled to labour". [5] The word appeared in several German-language descriptions of Indonesian zoology in the 17th century. It has been argued that the word comes specifically from the Banjarese variety of Malay, [4] but the age of the Old Javanese sources mentioned above make Old Malay a more likely origin for the term. Cribb and colleagues (2014) suggest that Bontius' account referred not to apes (as this description was from Java where the apes were not known from) but to humans suffering some serious medical condition (most likely cretinism) and that his use of the word was misunderstood by Nicolaes Tulp, who was the first to use the term in a publication a decade later. [6] :10–18 Robeson, Dave (1935). Al G. Barnes, Master Showman, as told by Al G. Barnes. Caldwell, Idaho: The Caxton Printers, Ltd. pp.102–103. LCCN 35012032. OCLC 598387. a b Didik, Prasetyo; Ancrenaz, Marc; Morrogh-Bernard, Helen C.; Atmoko, S. Suci Utami; Wich, Serge A.; van Schaik, Carel P. (2009). "Nest building in orangutans". In Wich, Serge A.; Atmoko, S. Suci Utami; Setia, Tatang Mitra; van Schaik, Carel P. (eds.). Orangutans: Geographic Variation in Behavioral Ecology and Conservation. Oxford University Press. pp.270–75. ISBN 978-0-19-921327-6. Archived from the original on 24 April 2016 . Retrieved 16 December 2015.

Another significant threat to orangutan survival is hunting for meat and capture of wild orangutans for sale into the pet trade. This practice is closely tied to what is called swidden agriculture: as locals burn fires to clear forested areas, orangutans within those areas flee from the conflagration and are captured for meat or sale. Dellios, Paulette (2008). "A lexical odyssey from the Malay World". Studia Universitatis Petru Maior. Philologia. 4 (4): 141–44. Hardus, M. E.; Lameira, A. R.; van Schaik, C. P.; Wich, S. A. (2009). "Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?". Proceedings of the Royal Society B. 276 (1673): 3689–94. doi: 10.1098/rspb.2009.1027. PMC 2817314. PMID 19656794.

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a b c d Ancrenaz, M.; Gumal, M.; Marshall, A. J.; Meijaard, E.; Wich, S. A.; Husson, S. (2016). "Pongo pygmaeus". IUCN Red List of Threatened Species. 2016: e.T17975A17966347. doi: 10.2305/IUCN.UK.2016-1.RLTS.T17975A17966347.en.