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). 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. 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. Starting with the 2004–2006 report, the title changed to "Primates in Peril: The World's 25 Most Endangered Primates". That same year, the list began to provide information about each species, including their conservation status and the threats they face in the wild. The species text is written in collaboration with experts from the field, with 60 people contributing to the 2006–2008 report and 85 people contributing to the 2008–2010 report. The 2004–2006 and 2006–2008 reports were published in the IUCN/SSC PSG journal Primate Conservation,, since then they have been published as independent publications.
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).
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." 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. 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.
Key +Key for column headingsSpeciesCommon and scientific name of the species, including a picture if availableYears listedYears the species has been included in the IUCN's list of the "Top 25 Most Endangered Primates"Location(s)Countries in which it is foundEstimated populationLatest population estimate from the IUCNIUCN statusConservation status of the species, per the IUCN as of the date of the latest list publicationThreatsA list of threats facing the species; used by the IUCN in assessing conservation status
Current list
+ The World's 25 Most Endangered Primates, 2018–2020: Madagascar Species Years listed Location(s) Estimated population IUCN status Threats Bemanasy mouse lemurMicrocebus manitatra 2018 Madagascar unknown loss of habitat (agricultural encroachment) Lac Alaotra bamboo lemurHapalemur alaotrensis 2000201420162018 Madagascar 2,500(2018 estimate) 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 lemurLepilemur jamesorum 20162018 Madagascar 1,386 (2010 estimate) habitat loss (shifting agriculture) hunting (bushmeat) live capture (pet trade) IndriIndri indri 20122018 Madagascar unknown loss of habitat (slash-and-burn agriculture, firewood) hunting (bushmeat, skins) Aye-ayeDaubentonia madagascariensis 20162018 Madagascar unknown 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 Species Years listed Location(s) Estimated population IUCN status Threats Rondo dwarf galagoGalagoides rondoensis 2006200820102012 Tanzania unknown very small range habitat loss and fragmentation (agricultural encroachment, charcoal production, logging) Roloway monkeyCercopithecus roloway 20022006200820102012 Côte d'IvoireGhana unknown hunting (bushmeat) habitat loss and fragmentation (agricultural encroachment, charcoal production, logging) Tana River red colobusPiliocolobus rufomitratus 20022004200620082012 Kenya 1,100–1,300 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 colobusPiliocolobus pennantii pennantii 2004200620102012 Equatorial Guinea (Bioko Island) fewer than 5,000 habitat degradation hunting (bushmeat) small range Eastern lowland gorillaGorilla beringei graueri 20102012 Democratic Republic of the Congo 6,800 (2021) 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 Species Years listed Location(s) Estimated population IUCN status Threats Javan slow lorisNycticebus javanicus 200820102012 Indonesia (Java) unknown live capture (pet trade [intense]) hunting (traditional medicine [intense]) habitat loss (agriculture, development activities [roads], human disturbance) Pig-tailed langurSimias concolor 200220042006200820102012 Indonesia (Mentawai Islands) 700–3,347 habitat loss (human encroachment, product extraction, commercial logging, conversion to cash crops and oil palm plantations) hunting (bushmeat) live capture (pet trade) Delacour's langurTrachypithecus delacouri 2000200220042006200820102012 Vietnam fewer than 250 habitat fragmentation hunting (bushmeat, traditional medicine) Golden-headed langurTrachypithecus poliocephalus 2000200220042006200820102012 Vietnam 60–70 habitat fragmentation (human encroachment, development for tourism) hunting (bushmeat, traditional medicine) Western purple-faced langurSemnopithecus vetulus nestor 20042006200820102012 Sri Lanka unknown 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 doucPygathrix cinerea 2000200220042006200820102012 Vietnam 600–700 restricted range habitat loss and fragmentation (agricultural encroachment, illegal logging, firewood) hunting (bushmeat, traditional medicine) live capture (pet trade) Tonkin snub-nosed monkeyRhinopithecus avunculus 2000200220042006200820102012 Vietnam 200–250 habitat loss and fragmentation (logging, firewood, roads) hunting (bushmeat, traditional medicine) Eastern black crested gibbonNomascus nasutus 200820102012 ChinaVietnam around 110 habitat loss, fragmentation, and disturbance (agricultural encroachment, pastoral farming, firewood, charcoal production) hunting (bushmeat) Pygmy tarsierTarsius pumilus 2012 Indonesia (Sulawesi) unknown habitat loss (human encroachment)
+ The World's 25 Most Endangered Primates, 2012–2014: Neotropics Species Years listed Location(s) Estimated population IUCN status Threats Brown spider monkeyAteles hybridus 20042006200820102012 ColombiaVenezuela unknown habitat loss and fragmentation (agricultural encroachment, cattle-ranching, logging) hunting (bushmeat) live capture (pet trade) Brown-headed spider monkeyAteles fusciceps fusciceps 20062012 Ecuador unknown habitat loss and fragmentation hunting (bushmeat) Kaapori capuchinCebus kaapori 2012 Brazil unknown habitat loss and degradation (selective logging) hunting (bushmeat) live capture (pet trade) Rio Mayo titiPlecturocebus oenanthe 2012 Peru unknown habitat loss and fragmentation (rice and coffee plantations, roads, cattle-ranching) hunting (bushmeat) live capture (pet trade) Northern brown howlerAlouatta guariba guariba 2012 Brazil fewer than 250 habitat loss (selective logging) hunting (bushmeat) disease epidemics
Former list members
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). 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. 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. 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.
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. The same approach was taken with the 2012–2014 list.
+ Primates formerly listed in the Top 25 Most Endangered Primates: Madagascar Species Years listed Location(s) Estimated population IUCN status Threats Greater bamboo lemurProlemur simus 20022004200620082010 Madagascar 500 or fewer 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 lemurVarecia variegata 2010 Madagascar unknown loss of habitat and fragmentation (slash-and-burn agriculture, mining, logging)