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The World's 25 Most Endangered Primates is a list of highly endangered primate species selected and published by the International Union for Conservation of Nature (IUCN) Species Survival Commission (SSC) Primate Specialist Group (PSG), the International Primatological Society (IPS), Global Wildlife Conservation (GWC), and Bristol Zoological Society (BZS).^[1] The IUCN/SSC PSG worked with Conservation International (CI) to start the list in 2000, but in 2002, during the 19th Congress of the International Primatological Society, primatologists reviewed and debated the list, resulting in the 2002–2004 revision and the endorsement of the IPS. The publication was a joint project between the three conservation organizations until the 2012–2014 list when BZS was added as a publisher.^[2] The 2018–2020 list was the first time Conservation International was not among the publishers, replaced instead by GWC. The list has been revised every two years following the biannual Congress of the IPS.^[1] Starting with the 2004–2006 report, the title changed to "Primates in Peril: The World's 25 Most Endangered Primates".^[3] That same year, the list began to provide information about each species, including their conservation status and the threats they face in the wild.^[4] The species text is written in collaboration with experts from the field, with 60 people contributing to the 2006–2008 report^[5] and 85 people contributing to the 2008–2010 report.^[4] The 2004–2006 and 2006–2008 reports were published in the IUCN/SSC PSG journal Primate Conservation,^[3][6], since then they have been published as independent publications.^{[4][7][2][8][9][1]}

The 25 species on the 2018–2020 list are distributed between 32 countries. The country with the most species on the list is Madagascar with five species, Indonesia, Brazil, Ghana, and Côte d'Ivoire each have three. The list is broken into four distinct regions: the island of Madagascar, the continent of Africa, the continent of Asia including the islands of Indonesia, and the Neotropics (Central and South America).^[1]

The purpose of the list, according to Russell Mittermeier, the president of CI, is "to highlight those [primate species] that are most at risk, to attract the attention of the public, to stimulate national governments to do more, and especially to find the resources to implement desperately needed conservation measures."^[10] Species are selected for the list based on two primary reasons: extremely small population sizes and very rapid drops in numbers. These reasons are heavily influenced by habitat loss and hunting, the two greatest threats primates face. More specifically, threats listed in the report include deforestation due to slash-and-burn agriculture, clearing for pasture or farmland, charcoal production, firewood production, illegal logging, selective logging, mining, land development, and cash crop production; forest fragmentation; small population sizes; live capture for the exotic pet trade; and hunting for bushmeat and traditional medicine.^[4] Twelve species were dropped for the 2018–2020 list, Mittermeier notes this was not because their situation has improved but instead to focus attention on other species that are also have "bleak prospects for their survival.^[1]

The World's 25 Most Endangered Primates, 2018–2020: Madagascar^[1]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Bemanasy mouse lemur Microcebus manitatra	2018	Madagascar	unknown	Critically Endangered[11]	loss of habitat (agricultural encroachment)
Lac Alaotra bamboo lemur Hapalemur alaotrensis	2000 2014 2016 2018	Madagascar	2,500 (2018 estimate)	Critically Endangered[12]	loss of habitat (agricultural encroachment, burning of marshlands [to create rice paddies, catch fish, and for cattle grazing] hunting (bushmeat) live capture (local pet trade)
James' sportive lemur Lepilemur jamesorum	2016 2018	Madagascar	1,386 (2010 estimate)	Critically Endangered[13]	habitat loss (shifting agriculture) hunting (bushmeat) live capture (pet trade)
Indri Indri indri	2012 2018	Madagascar	unknown	Critically Endangered[14]	loss of habitat (slash-and-burn agriculture, firewood) hunting (bushmeat, skins)
Aye-aye Daubentonia madagascariensis	2016 2018	Madagascar	unknown	Endangered[15]	habitat loss (selective logging for local use [boats, houses, coffins], agricultural encroachment, fire) hunting (pests, local taboos, bushmeat)

The World's 25 Most Endangered Primates, 2012–2014: Africa^[2]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Rondo dwarf galago Galagoides rondoensis	2006 2008 2010 2012	Tanzania	unknown	Critically Endangered[16]	very small range habitat loss and fragmentation (agricultural encroachment, charcoal production, logging)
Roloway monkey Cercopithecus roloway	2002 2006 2008 2010 2012	Côte d'Ivoire Ghana	unknown	Endangered[17]	hunting (bushmeat) habitat loss and fragmentation (agricultural encroachment, charcoal production, logging)
Tana River red colobus Procolobus rufomitratus	2002 2004 2006 2008 2012	Kenya	1,100–1,300	Endangered[18]	hunting (bushmeat) habitat loss and fragmentation (agricultural encroachment, fire, firewood, selective logging for local use [houses, canoes]) habitat degradation (livestock, dam construction, irrigation projects) parasitic infection of isolated populations
Bioko red colobus Piliocolobus pennantii pennantii	2004 2006 2010 2012	Equatorial Guinea (Bioko Island)	fewer than 5,000	Endangered[19]	habitat degradation hunting (bushmeat) small range
Eastern lowland gorilla Gorilla beringei graueri	2010 2012	Democratic Republic of the Congo	5,000	Critically Endangered[20]	habitat loss and fragmentation (agricultural encroachment, pastoral farming, illegal mining, charcoal production, wood and bamboo harvesting) hunting (bushmeat, infant capture)

The World's 25 Most Endangered Primates, 2012–2014: Asia^[2]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Javan slow loris Nycticebus javanicus	2008 2010 2012	Indonesia (Java)	unknown	Critically Endangered[21]	live capture (pet trade [intense]) hunting (traditional medicine [intense]) habitat loss (agriculture, development activities [roads], human disturbance)
Pig-tailed langur Simias concolor	2002 2004 2006 2008 2010 2012	Indonesia (Mentawai Islands)	700–3,347	Critically Endangered[22]	habitat loss (human encroachment, product extraction, commercial logging, conversion to cash crops and oil palm plantations) hunting (bushmeat) live capture (pet trade)
Delacour's langur Trachypithecus delacouri	2000 2002 2004 2006 2008 2010 2012	Vietnam	fewer than 250	Critically Endangered[23]	habitat fragmentation hunting (bushmeat, traditional medicine)
Golden-headed langur Trachypithecus poliocephalus	2000 2002 2004 2006 2008 2010 2012	Vietnam	60–70	Critically Endangered[24]	habitat fragmentation (human encroachment, development for tourism) hunting (bushmeat, traditional medicine)
Western purple-faced langur Semnopithecus vetulus nestor	2004 2006 2008 2010 2012	Sri Lanka	unknown	Critically Endangered[25]	habitat loss and fragmentation (urbanization, agricultural encroachment) dependent on gardens for survival live capture (pet trade) hunting (pests) other human factors (electrocution [power lines], road kill, dog attacks)
Grey-shanked douc Pygathrix cinerea	2000 2002 2004 2006 2008 2010 2012	Vietnam	600–700	Critically Endangered[26]	restricted range habitat loss and fragmentation (agricultural encroachment, illegal logging, firewood) hunting (bushmeat, traditional medicine) live capture (pet trade)
Tonkin snub-nosed monkey Rhinopithecus avunculus	2000 2002 2004 2006 2008 2010 2012	Vietnam	200–250	Critically Endangered[27]	habitat loss and fragmentation (logging, firewood, roads) hunting (bushmeat, traditional medicine)
Eastern black crested gibbon Nomascus nasutus	2008 2010 2012	China Vietnam	around 110	Critically Endangered[28]	habitat loss, fragmentation, and disturbance (agricultural encroachment, pastoral farming, firewood, charcoal production) hunting (bushmeat)
Pygmy tarsier Tarsius pumilus	2012	Indonesia (Sulawesi)	unknown	Data deficient[29]	habitat loss (human encroachment)

The World's 25 Most Endangered Primates, 2012–2014: Neotropics^[2]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Brown spider monkey Ateles hybridus	2004[N 1] 2006 2008 2010 2012	Colombia Venezuela	unknown	Critically Endangered[30]	habitat loss and fragmentation (agricultural encroachment, cattle-ranching, logging) hunting (bushmeat) live capture (pet trade)
Brown-headed spider monkey Ateles fusciceps fusciceps	2006 2012	Ecuador	unknown	Critically Endangered[31]	habitat loss and fragmentation hunting (bushmeat)
Kaapori capuchin Cebus kaapori	2012	Brazil	unknown	Critically Endangered[32]	habitat loss and degradation (selective logging) hunting (bushmeat) live capture (pet trade)
Rio Mayo titi Callicebus oenanthe	2012	Peru	unknown	Critically Endangered[33]	habitat loss and fragmentation (rice and coffee plantations, roads, cattle-ranching) hunting (bushmeat) live capture (pet trade)
Northern brown howler Alouatta guariba guariba	2012	Brazil	fewer than 250	Critically Endangered[34]	habitat loss (selective logging) hunting (bushmeat) disease epidemics

With each new publication, species are both added and removed from the list. In some cases, removal from the list signifies improvement for the species. With the publication of the 2006–2008 list, four species were removed because of increased conservation efforts: the black lion tamarin (Leontopithecus chrysopygus), golden lion tamarin (Leontopithecus rosalia), mountain gorilla (Gorilla beringei beringei), and Perrier's sifaka (Propithecus perrieri).^[35] In 2008, the black lion tamarin went from critically endangered to endangered and the golden lion tamarin was similarly promoted in 2003 after three decades of collaborative conservation efforts by zoos and other institutions. Well-protected species such as these still have very small populations, and due to deforestation, new habitat is still needed for their long-term survival.^[10] The Hainan black crested gibbon (Nomascus hainanus), which was removed from the 2008–2010 list, still has fewer than 20 individuals left, but significant efforts to protect it are now being made.^[4] Mittermeier claimed in 2007 that all 25 species could be elevated off the list within five to ten years if conservation organizations had the necessary resources.^[35]

Unlike the changes in the 2006–2008 report, not all species were removed from the 2008–2010 list due to improvement in their situation. Instead, new species were added to bring attention to other closely related species with very small populations that are also at risk of extinction. For example, the highly endangered eastern black crested gibbon (Nomascus nasutus) replaced the Hainan black crested gibbon. The Javan slow loris (Nycticebus javanicus) replaced the Horton Plains slender loris (Loris tardigradus nycticeboides) because the former has been hit the hardest of Asian lorises, all of which are declining rapidly due primarily to capture for the exotic pet trade, as well as use in traditional medicines and forest loss. In another case, the brown-headed spider monkey (Ateles fusciceps fusciceps) was omitted from the list since no spokesperson could be found for the species.^[4] The same approach was taken with the 2012–2014 list.^[2]

Primates formerly listed in the Top 25 Most Endangered Primates: Madagascar^{[4][7][2][8][9]}

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Greater bamboo lemur Prolemur simus	2002 2004 2006 2008 2010	Madagascar	500 or fewer	Critically Endangered[36]	small, isolated populations loss of habitat and fragmentation (slash-and-burn agriculture, mining, illegal logging, cutting of bamboo) hunting (bushmeat) reduced availability of drinking water due to climatic change extreme dietary specialization and dependency on giant bamboo
Black-and-white ruffed lemur Varecia variegata	2010	Madagascar	unknown	Critically Endangered[37]	loss of habitat and fragmentation (slash-and-burn agriculture, mining, logging) hunting (bushmeat)
Gray-headed lemur Eulemur cinereiceps	2004 2006 2008	Madagascar	7,265 ± 2,268	Endangered[38]	very small range (~700 km2) hybridization with red-fronted lemur (E. rufifrons) low population densities habitat loss and fragmentation (fragmented, small populations) cyclones hunting (bushmeat)
Golden-crowned sifaka Propithecus tattersalli	2000	Madagascar	6,000–10,000[39]	Endangered[39]	hunting (by gold miners) loss of habitat (slash-and-burn agriculture, uncontrolled grass fires, wood extraction [housing & firewood], selective logging, gold mining)[39]
Golden bamboo lemur Hapalemur aureus	2000	Madagascar	fewer than 5,916[40]	Endangered[40]	loss of habitat (slash-and-burn agriculture, cutting of bamboo [for building houses, carrying water, making baskets and other local uses]) hunting (bushmeat)[40]
Sahamalaza sportive lemur Lepilemur sahamalazensis	2006	Madagascar	unknown	Data deficient[41]	loss of habitat (agricultural encroachment, charcoal production, selective logging for local use [houses]) hunting (bushmeat)[41]
Perrier's sifaka Propithecus perrieri	2000 2002 2004 2014 2016	Madagascar	around 915[42]	Critically Endangered[42]	loss of habitat (slash-and-burn agriculture, charcoal production, fires to clear forest for pasture, mining) hunting (bushmeat)[42]
Blue-eyed black lemur Eulemur flavifrons	2008 2010 2012	Madagascar	450–2,300	Critically Endangered[43]	very small range (~2,700 km2) loss of habitat (slash-and-burn agriculture, selective logging) hunting (bushmeat) live capture (pet trade)
Northern sportive lemur Lepilemur septentrionalis	2008 2010 2012	Madagascar	around 19	Critically Endangered[44]	very small range habitat loss (firewood, charcoal production, Eucalyptus plantations) hunting (bushmeat)
Silky sifaka Propithecus candidus	2000 2002 2004 2006 2008 2010 2012	Madagascar	fewer than 250	Critically Endangered[45]	very small range hunting (bushmeat) habitat loss (slash-and-burn agriculture, illegal logging, firewood)
Madame Berthe's mouse lemur Microcebus berthae	2012	Madagascar	fewer than 8,000	Critically Endangered[46]	loss of habitat and fragmentation (slash-and-burn agriculture, illegal logging)
Red ruffed lemur Varecia rubra	2012	Madagascar	unknown	Critically Endangered[47]	loss of habitat (slash-and-burn agriculture, illegal logging, human encroachment) hunting (bushmeat)
Lavasoa Mountains dwarf lemur Cheirogaleus lavasoensis	2014	Madagascar	?[48]	Endangered[48]
Gerp's mouse lemur Microcebus gerpi	2016	Madagascar	?[49]	Critically Endangered[49]
Ring-tailed lemur Lemur catta	2016	Madagascar	?[50]	Endangered[50]

Primates formerly listed in the Top 25 Most Endangered Primates: Africa^[4][2]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Mount Rungwe galago Galagoides sp.	2004	Tanzania	unknown	Not evaluated	loss of habitat (logging, agricultural encroachment, charcoal production) hunting (bushmeat)[3]
Sclater's guenon Cercopithecus sclateri	2000	Nigeria	unknown	Vulnerable[51]	habitat loss and fragmentation (logging, agricultural encroachment, oil exploration) high human density hunting (bushmeat)[51]
Drill Mandrillus leucophaeus	2000	Cameroon Equatorial Guinea (Bioko) Nigeria	unknown	Endangered[52]	small range loss of habitat (clearcutting [for chipboard factories and settlement]) hunting (bushmeat, persecution as pests)[52]
Tana River mangabey Cercocebus galeritus galeritus	2002	Kenya	1,000–1,200[53]	Endangered[53]	loss of habitat (palm oil production, logging, agricultural encroachment, grass fires intended to prevent forest regeneration, overgrazing, damming and irrigation projects) hunting (persecution as pests)[53]
Sanje mangabey Cercocebus sanjei	2000 2002 2004	Tanzania	fewer than 1,300[54]	Endangered[54]	loss of habitat (logging, charcoal production) hunting (persecution as pests)[54]
Sooty mangabey Cercocebus atys lunulatus	2000 2002 2004	Côte d'Ivoire Ghana	unknown	Endangered[55]	habitat loss and degradation hunting (bushmeat)[55]
Miss Waldron's red colobus Piliocolobus badius waldronae	2000 2002 2006	Côte d'Ivoire Ghana	unknown	Critically Endangered[56]	very small populations (recent, very rapid declines in numbers) habitat loss hunting (bushmeat)[56]
Mountain gorilla Gorilla beringei beringei	2000 2002 2004	Rwanda Uganda	around 880	Critically Endangered[57]	two isolated populations political instability human diseases hunting (bushmeat)[57]
Niger Delta red colobus Procolobus epieni	2008 2010	Nigeria	unknown	Critically Endangered[58]	very small range (~1,500 km2) hunting (bushmeat) habitat loss and degradation (logging of important food trees, loss of marsh forests due to canal construction)
Kipunji Rungwecebus kipunji	2006 2008	Tanzania	around 1,117	Critically Endangered[59]	very small range habitat loss and fragmentation hunting (bushmeat)
Cross River gorilla Gorilla gorilla diehli	2000 2002 2004 2006 2008	Cameroon Nigeria	200–300	Critically Endangered[60]	small, restricted range habitat loss (agricultural encroachment, fires to clear forest or improve pasture, development activities [roads]) hunting (bushmeat, wire snares set for other wildlife)

Primates formerly listed in the Top 25 Most Endangered Primates: Asia^[4]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Horton Plains slender loris Loris tardigradus nycticeboides	2004 2006	Sri Lanka	unknown	Endangered[61]	five isolated populations habitat loss hunting (bushmeat)[61]
Natuna Island surili Presbytis natunae	2002	Indonesia	fewer than 10,000[62]	Vulnerable[62]	two isolated populations habitat loss and degradation live capture (pet trade)[62]
White-headed langur Trachypithecus poliocephalus leucocephalus	2002	China, Vietnam	fewer than 250	Critically Endangered[63]	very small populations (recent, very rapid declines in numbers) habitat loss hunting[63]
Miller's grizzled langur Presbytis hosei canicrus	2004	Indonesia (Kalimantan)	unknown	Endangered[64]	habitat loss and fragmentation hunting[64]
Black snub-nosed monkey Rhinopithecus bieti	2002	China	fewer than 2,000[65]	Endangered[65]	habitat loss (logging, fires for agricultural use, pasture) pesticide use hunting (non-targeted [snares])[65]
Gray snub-nosed monkey Rhinopithecus brelichi	2002	China	around 750[66]	Endangered[66]	one isolated population (vulnerable to epidemic disease or catastrophes) habitat loss (forest clearing, development for tourism, agricultural expansion, firewood) hunting (non-targeted)[66]
Silvery gibbon Hylobates moloch	2000	Indonesia (Java)	4,000–4,500[67]	Endangered[67]	habitat loss and fragmentation live capture (pet trade)[67]
Hainan black crested gibbon Nomascus hainanus	2000 2004 2006	China (Hainan)	around 20[68]	Critically Endangered[68]	extremely small population size suboptimal, protected habitat possible gender bias in recent births hunting (bushmeat)[68]
Siau Island tarsier Tarsius tumpara	2006 2008 2010	Indonesia (Siau Island)	Low thousands at best	Not evaluated	island population (near an active volcano) very small range high human density hunting [bushmeat (used as snack food)] habitat degradation
Western hoolock gibbon Hoolock hoolock	2006 2008	Bangladesh India Myanmar	fewer than 5,000	Endangered[69]	very small populations (recent, very rapid declines in numbers) habitat loss and fragmentation (human encroachment, tea plantations, slash-and-burn cultivation) hunting (bushmeat, traditional medicine) live capture (pet trade)
Sumatran orangutan Pongo abelii	2000 2002 2004 2006 2008	Indonesia (Sumatra)	around 6,600	Critically Endangered[70]	recent, very rapid declines in numbers only 10 fragmented habitat units habitat loss and fragmentation (fires, agriculture and oil palm plantations, roads, logging, encroachment) hunting (pests, bushmeat) [occasional] live capture (pet trade) [occasional]
Northwest Bornean orangutan Pongo pygmaeus pygmaeus	2010	Indonesia (West Kalimantan, Borneo) Malaysia (Sarawak)	unknown	Endangered[71]	habitat loss and fragmentation (fires, agriculture and oil palm plantations, roads, logging, encroachment) hunting (pests, bushmeat, traditional medicine) live capture (pet trade)
Lion-tailed macaque Macaca silenus	2010	India	fewer than 4,000	Endangered[72]	habitat loss and fragmentation (agriculture and tea/coffee plantations, logging) hunting (bushmeat, traditional medicine)

Primates formerly listed in the Top 25 Most Endangered Primates: Neotropics^[4]

Species	Years listed	Location(s)	Estimated population	IUCN status	Threats
Golden lion tamarin Leontopithecus rosalia	2000	Brazil (Rio de Janeiro)	3,200[73]	Endangered[73]	habitat loss and fragmentation (fires to clear forest for pasture) live capture (pet trade)[73]
Black lion tamarin Leontopithecus chrysopygus	2000	Brazil (São Paulo)	around 1,000[74]	Endangered[74]	small population size (11 isolated populations, but only one is viable) habitat loss and fragmentation[74]
Superagui lion tamarin Leontopithecus caissara	2000 2002 2004	Brazil (Paraná and São Paulo)	fewer than 400[75]	Critically Endangered[75]	small, isolated populations habitat loss and degradation (agricultural encroachment, palm heart harvesting, tourism) high human density (increased squatting by impoverished people, land speculation) hunting (bushmeat)[75]
Golden-bellied capuchin Cebus xanthosternos	2000 2002 2004	Brazil (Bahia, Minas Gerais?)	unknown	Critically Endangered[76]	habitat loss hunting (bushmeat)[76]
Northern muriqui Brachyteles hypoxanthus	2000 2002 2004	Brazil (Bahia, Espírito Santo, Minas Gerais)	fewer than 1,000[77]	Critically Endangered[77]	small, isolated populations habitat loss and fragmentation hunting (bushmeat [past], sport [past])[77]
Yellow-tailed woolly monkey Oreonax flavicauda	2000 2006 2008 2010	Peru	unknown	Critically Endangered[78]	restricted range low population densities habitat loss (agriculture, logging, roads, colonization) hunting (bushmeat, fur) live capture (pet trade)
Cotton-top tamarin Saguinus oedipus	2008	Colombia	fewer than 6,000	Critically Endangered[79]	habitat loss and fragmentation (large-scale agricultural production [cattle] and farming, logging, oil palm plantations, hydroelectric projects) live capture (pet trade [current], biomedical research [past])
Blond capuchin Cebus flavius	2010	Brazil	180	Critically Endangered[80]	habitat loss and fragmentation (coastal development and sugar cane plantations) live capture (pet trade) hunting (bushmeat)

With the exception of the 2000–2002 publication, which was written collaboratively by the IUCN/SSC PSG and CI, the list has been revised every two years following the biannual Congress of the IPS. The 2002–2004 list resulted from the 19th Congress of the IPS in Beijing, China; the 2004–2006 list followed the 20th Congress of the IPS, held in Torino, Italy; the 2006–2008 list after the 21st Congress in Entebbe, Uganda; the 2008–2010 list followed the 22nd Congress held in Edinburgh, UK; the 2010-2012 list followed the 23rd Congress in Kyoto, Japan; the 2012–2014 list after the 24th Congress in Cancún, Mexico; the 2014–2016 list after the 25th Congress in Hanoi, Vietnam; the 2016–2018 list after the 26th Congress in Chicago, US; the 2018–2020 list after the 27th Congress in Nairobi, Kenya; and the 2022–2023 list after the 28th Congress in Quito, Ecuador.^[4]

The 2008 IUCN Red List of Threatened Species offered assessments of 634 primate taxa, of which 303 (47.8%) were listed as threatened (vulnerable, endangered, or critically endangered). A total of 206 primate species were ranked as either critically endangered or endangered, 54 (26%) of which have been included at least once in The World's 25 Most Endangered Primates since 2000.^[4]

• The world's 100 most threatened species
• List of primates by population

• IUCN Primate Specialist Group's Special Reports containing the latest and historic reports.