IUCN Top 25: The world’s most endangered primates

The International Union for Conservation of Nature (IUCN), together with the International Primatological Society and Re:wild, has published the new list of the world’s 25 most endangered primates for the period 2023–2025. This now twelfth edition of the report Primates in Peril: The World’s 25 Most Endangered Primates 2023-2025, which deals with monkeys, prosimians and great apes, is not only an appeal to the global community but also a reflection of alarming developments in primate habitats worldwide.

A global look at the threat situation

The current edition of the Top25 Most Endangered Primates covers species from all major primate regions: six species each come from Africa and the Neotropics, nine from Asia and four from Madagascar. Countries with exceptionally high endemic biodiversity such as Indonesia, Madagascar, Vietnam and China are particularly affected. In total, 15 species were added to the list – eight of them appear for the very first time.

However, the fact that a species has been replaced on the list does not necessarily mean an improvement in its situation. On the contrary: many of the removed species are still considered critically endangered. The aim of the list is therefore not to provide a complete overview or to document progress, but to draw targeted attention to selected, often overlooked species whose situation is just as critical.

Although the report speaks of the “25 most endangered primates”, it actually includes significantly more species. In addition to the main list, other highly threatened species are also listed – so-called Other Species Considered. These were either covered in previous editions or their level of threat is considered comparably severe. Their mention shows how far-reaching the crisis in primate conservation has become.

Threat factors: habitat loss, hunting and the climate crisis

The decline of many primate species is dramatic – and the causes are diverse but well known: the loss and fragmentation of habitats due to deforestation, agriculture and infrastructure projects are among the greatest threats. Added to this is illegal hunting – often for the meat trade or the pet trade – as well as increasing conflicts with humans, for example during harvests on plantations. Climate change further exacerbates many of these problems, for instance through more frequent extreme weather events such as droughts or cyclones.

Species with an already small range are particularly at risk. Many critically endangered primates occur only in very limited regions – for example on individual islands or in isolated mountain forests. Even small-scale interventions, such as building a road or a dam, can have serious consequences there. Social structures within groups also suffer from the decline: if only a few animals survive, reproduction rates drop, conflicts increase and genetic exchange comes to a standstill.

Some species have only recently been scientifically described – and are already on the verge of extinction. Others were long considered common but are increasingly disappearing from their native habitat. In many cases, protected areas exist on paper, but a lack of resources, political instability or weak enforcement often causes effective protection to fail. The threats are complex – all the more important to look closely at each species and its specific situation.

Top 25 of the world’s most endangered primates

The selection of the 25 species is therefore not to be understood as an objective ranking, but as the result of intensive expert consultation, strategic weighing of priorities and international collaboration. The list is meant to be a wake-up call – and to focus attention on those species for which time is especially running out.

Madame Berthe’s mouse lemur (Microcebus berthae) – Madagascar – estimated population: < 8,000 animals (2005)

The smallest primate known in the world lives exclusively in the dry forests of Kirindy and Ambadira in western Madagascar. As early as 2019, a locally monitored population in Kirindy was reported extinct. The species is sensitive to habitat loss caused by slash-and-burn clearing, charcoal production and illegal logging.

The species avoids heavily degraded forests and therefore depends on intact, contiguous forest areas. If deforestation continues at the current rate, it risks losing its entire habitat within the next decade. In addition, it faces competition from other mouse lemurs, with which it must compete for resources in highly fragmented forests.

Northern sportive lemur (Lepilemur septentrionalis) – Madagascar – population approx. 50–70 animals

The species’ population has fallen by more than 80 % over the past 20 years. Today, the nocturnal, strictly herbivorous northern sportive lemur lives only in the highly fragmented forest area of Montagne des Français at the northern tip of Madagascar.

The main threats are the loss of its habitat through illegal charcoal production and the hunting of the animals as bushmeat. In former range areas such as Sahafary and Analalava, the species is now considered extinct. There is still no captive-breeding program – protecting the remaining habitat is therefore the last chance for the survival of this rare species.

Coquerel’s giant mouse lemur (Mirza coquereli) – Madagascar – estimated decline: > 50 % over three generations

This nocturnal lemur species inhabits the dry deciduous forests of western Madagascar, but today occurs only in highly fragmented remnant populations. In undisturbed forests such as Kirindy, up to 120 individuals per square kilometer used to be counted – by now, populations there have shrunk considerably.

The main causes are the ongoing destruction of its habitat through slash-and-burn clearing, illegal charcoal production and poaching. Added to this are bushmeat hunting and increasing human settlement pressure. Because deforestation continues unabated and population growth is rapid, a further decline of at least 50 % is projected – leaving the species’ future uncertain.

Red ruffed lemur (Varecia rubra) – Madagascar – suspected decline: ≥ 80 % in 24 years

The red ruffed lemur lives in the evergreen rainforests of the Masoala Peninsula in northeastern Madagascar. Its population density varies widely and is much higher in intact forest areas than near human settlements. The species suffers massively from habitat loss caused by slash-and-burn clearing for subsistence agriculture, illegal timber trade (e.g. rosewood) and increasingly frequent cyclones that devastate large areas of forest. Added to this is heavy hunting for the local meat market.

Particularly alarming is the ongoing fragmentation of its habitat, which isolates remaining populations from one another and reduces genetic diversity. Without effective protection measures, the loss of large parts of the population in the coming decades is likely.

Rondo dwarf galago (Paragalago rondoensis) – Tanzania – population unknown

The smallest of all galagos lives exclusively in the highly fragmented coastal forests of Tanzania. The species inhabits small, isolated forest islands in up to three regions that are far apart. The main threats are habitat loss due to charcoal production, agriculture and infrastructure projects. In some areas, the forest has almost completely disappeared. Although there are protected areas such as the Rondo Nature Reserve or Pande GR, many populations are considered unstable. Population figures are not precisely known, but occurrences continue to shrink – with local extinctions in several former habitats.

Golden-bellied mangabey (Cercocebus chrysogaster) – DR Congo – population unknown

The golden-bellied mangabey lives in two regions that are far apart in the Democratic Republic of the Congo. For decades it was common in some areas; today, large groups are hardly observed anymore. Over the past 20 years, at least 32 % of its habitat has been destroyed, and in a further 7 % the species has already disappeared.

Particularly alarming is the commercial bushmeat trade: in some markets, golden-bellied mangabeys made up as much as 70 % of what was on offer. Entire groups are deliberately slaughtered. In addition, industrial logging threatens around 30 % of its range. A decline of at least 50 % is expected by 2029. Illegal pet trade also puts pressure on the species: juveniles are regularly offered at markets in Kinshasa and Lusambo, usually as bycatch of the bushmeat trade. Some reach South Africa or Asia via smuggling routes. Between 2018 and 2022, 120 wild-caught animals from the DR Congo were officially exported – additional pressure on already severely depleted populations.

Southern patas monkey (Erythrocebus baumstarki) – Tanzania – 80–200 individuals

The southern patas monkey is one of the rarest primate species in Africa – its numbers have collapsed dramatically over recent decades. Today, probably only 80 to 200 individuals remain, spread across small, often isolated groups in western Tanzania, especially in the western Serengeti ecosystem. In former range areas, the species is considered gone.

The main causes of the decline are the loss and fragmentation of its habitat due to agricultural expansion, charcoal production, livestock grazing and the construction of settlements and roads. Increasing competition with livestock at water sources also has a negative impact. In addition, patas monkeys are hunted – whether for their meat, for traditional ceremonies or in retaliation for alleged crop damage. Particularly problematic is the rapid population growth in the region, which further increases pressure on the last refuges. Without targeted conservation measures, this distinctive savanna primate is at risk of going extinct in the near future.

Red-bellied monkey (Cercopithecus erythrogaster) – Nigeria, Benin & Togo – population decline ≥ 50 % in 25 years

The shy and barely studied red-bellied monkey lives in small, scattered forest remnants in West Africa. Especially in Nigeria it still inhabits larger areas, but even there rainforests are shrinking rapidly – since 1990 alone, more than half of its habitat has been lost. Added to this is intensive hunting for bushmeat, which has increased with the decline of larger monkey species.

Particularly worrying: hunting for its meat is sometimes organized via social-media apps and carried out with dogs. In Togo, a planned dam threatens its habitat in the Togodo Forest. A decline of the total population by at least 50 % over three generations is likely – without consistent protection, this trend will continue.

Niger Delta red colobus (Piliocolobus epieni) – Nigeria – probably a few hundred animals

Discovered only in 1993, the Niger Delta red colobus was initially considered relatively common – but just a few years later it had disappeared from many of its original sites. Habitat loss through small-scale logging, the expansion of settlements, activities of the oil industry and altered waterways have severely damaged the forests in the Niger Delta. In many areas, large and medium-sized trees that serve as food plants are now missing. High human in-migration into the region further increases pressure on the last refuges.

The current population is likely only in the low hundreds – perhaps only a few viable groups remain. While targeted hunting has so far been rare, pressure from local use is rising rapidly. Conservation measures such as reforestation, habitat connectivity and education are urgently needed to prevent the species from disappearing entirely.

Cross River gorilla (Gorilla gorilla diehli) – Nigeria & Cameroon – <250 animals

The Cross River gorilla is the most endangered subspecies of all great apes. An estimated fewer than 250 adult individuals live in eleven isolated forest areas along the Nigeria–Cameroon border. Although around 70 % of its range lies within protected areas, habitat loss, fragmentation, road building and forest fires are leading to ever-increasing fragmentation. Genetic exchange between subpopulations is hardly possible anymore.

Political unrest in Cameroon also makes access for conservation measures difficult and has probably led to renewed hunting. The illegal shooting of even individual animals is particularly critical given the small population size. Although camera traps in Nigeria occasionally show offspring, without international cooperation, improved habitat connectivity and updated population data, this subspecies risks extinction.

Northern pygmy loris (Xanthonycticebus intermedius) – Vietnam, Laos & China – decline > 50 % in 20 years

The northern pygmy loris is highly threatened and is already considered gone from many parts of its range. In Vietnam, population densities are extremely low; in Laos and China, recent records are missing in many places. Even in protected areas, encounters are rare – in some cases, comprehensive surveys over years did not record a single animal.

The main threats are habitat loss and intensive hunting: in Vietnam, the species is killed for traditional medicine because of its supposed healing powers, captured for the pet trade and hunted for consumption. Internationally, the intermediate slow loris is also among the most frequently traded primate species. Many animals end up on social media as “cute pets”, but the trade is mostly based on wild capture. Without effective conservation measures, a further decline of more than 50 % over the coming decades is likely.

Sangihe tarsier (Tarsius sangirensis) – Sangihe Island (Indonesia) – at most 2,800 viable animals

The tiny, nocturnal Sangihe tarsier lives exclusively on the remote Indonesian island of Sangihe – an isolated volcanic arc between Sulawesi and the Philippines. With an area of less than 550 km², Sangihe is smaller than Singapore, and almost all of the original forest has now been fragmented or lost due to agriculture, settlement expansion and slash-and-burn clearing. Today, the species occurs almost only on the extinct volcano Mt. Sahendaruman, where the last larger forest area remains – but even this is part of a controversial gold-mining concession.

Another risk factor is the active volcano Mt. Awu, one of the most dangerous in Indonesia. It threatens not only the remaining forests but also the entire island population. Estimates suggest that at most 2,800 viable individuals could exist – probably far fewer, as many subhabitats are too small or too degraded to support stable groups. The species lives in monogamous family groups with small home ranges, depends on undisturbed forest structure and is extremely sensitive to disturbance. A single catastrophic event – whether a volcanic eruption, large-scale clear-cutting or the start of industrial mining – could mean the extinction of the entire species. At present, neither a protected area nor a breeding program exists.

Cat Ba langur (Trachypithecus poliocephalus) – Cat Ba Island (Vietnam) – approx. 90 animals

The Cat Ba langur is Vietnam’s rarest primate and lives exclusively on the island of the same name in Ha Long Bay. The current population is around 90 animals (as of mid 2024), spread across three small groups – only two of which reproduce. The species is highly specialized on karst limestone mountains and highly fragmented habitats. A surplus of males and group breakups regularly lead to conflict, infanticide and reproductive failure.

Although the region is under national and international protection (including UNESCO World Natural Heritage), enforcement remains weak. Tourism, settlement pressure and poaching – for example for traditional medicine – continue to endanger the species. Supported by German zoos, a conservation program has been running since 2000. Thanks to these measures, the population is slowly increasing, but the situation remains critical due to low reproduction rates, lack of genetic mixing and insufficient habitat connectivity.

Pig-tailed langur (Simias concolor) – Mentawai Islands (Indonesia) – decline > 80 %

The pig-tailed langur is one of the most endangered primate species in Southeast Asia. Since 1980, its total population has shrunk by more than 80 %. The subspecies S. c. concolor on the Pagai Islands now numbers only 700 to 1,800 individuals and may already be locally extinct. The Siberut subspecies (S. c. siberu) also suffers from heavy hunting: in a recent interview, more than 1,600 animals were reported as the annual hunting take – up to 50 % of the estimated population.

The main causes are poaching, commercial logging and the conversion of rainforest into oil palm plantations. Even in protected areas such as Siberut National Park, populations are declining. The species is preferentially hunted, whether for cultural, ritual or economic reasons.

Myanmar snub-nosed monkey (Rhinopithecus strykeri) – Myanmar & China – < 950 animals

The rare Myanmar snub-nosed monkey was only scientifically described in 2010. It lives in hard-to-reach mountain forests on the border between Myanmar and China. The total population is estimated at fewer than 950 individuals, divided into small, isolated groups. Most records come from camera traps or reports by local supporters.

The main threats are habitat destruction through large-scale logging, road building and dam projects. Mechanical logging reaches elevations above 2,000 m – precisely those regions where the animals rely on lichens in winter. They also often get caught in wire snares that are actually set for wild boar or deer. As infrastructure expands, pressure from poaching and the local bushmeat trade also increases. Without massive conservation measures, a population decline of more than 80 % over the next 30 years is feared.

Raffles’ banded langur (Presbytis femoralis) – Singapore & Malaysia – a few hundred animals

Raffles’ banded langur is now found only in highly isolated forest areas in Southeast Asia. In Singapore, there are only around 70 individuals in the Central Catchment Nature Reserve – a population with low genetic diversity. In Malaysia, a few hundred animals live in separate forests, especially in the state of Johor.

The main threats are habitat loss due to urbanization, oil palm plantations and infrastructure projects. Roads, power lines and settlements further fragment the habitat of Raffles’ banded langur. Animals repeatedly die in traffic or from electrocution while searching for new habitat.

Sarawak surili (Presbytis chrysomelas) – Malaysia & possibly Indonesia – 200–500 animals

The Sarawak surili used to be widespread, but today it is confirmed only at a few isolated sites in Sarawak – including Maludam, Samunsam, Tanjung Datu and Similajau. The total population is estimated at only 200 to 500 individuals. The main threat is habitat loss through large-scale conversion of rainforest into oil palm plantations. Many former occurrence areas are now considered abandoned. Infrastructure projects and selective logging also contribute to the fragmentation of the remaining forest areas.

Although the species is protected in Sarawak, effective conservation measures have so far been insufficient. In addition, its exact distribution is still unclear, as is the taxonomic distinction from related species. There is therefore an urgent need for research and action to secure remaining populations and ensure its long-term survival.

Eastern black crested gibbon (Nomascus nasutus) – Vietnam & China – approx. 130 animals

The species was long thought to be extinct until a surviving population was discovered in northeastern Vietnam in 2002. Today, around 130 individuals live in about two dozen groups along the Vietnam–China border – the only known population of this species. Thanks to protection measures and monitoring, numbers seem to be slowly increasing, but the species remains critically endangered.

Main threats are habitat loss, firewood collection, livestock grazing and possible inbreeding in the isolated remnant population. Further decline or occasional hunting could seriously endanger its continued survival.

Tapanuli orangutan (Pongo tapanuliensis) – Sumatra (Indonesia) – < 800 animals

With fewer than 800 individuals, the Tapanuli orangutan – only scientifically described in 2017 – is the rarest of all great ape species. It occurs exclusively in the Batang Toru forest complex in northern Sumatra. The species is genetically isolated and already shows signs of inbreeding, which further threatens its long-term viability.

Only about 10 % of its range lies in nationally recognized protected areas. Large parts are designated as “protection forest”, but illegal logging, settlement pressure and poaching are advancing even there. Current infrastructure projects are particularly problematic: a planned hydropower plant threatens about 10 % of the remaining habitat, including the densest populations. Added to this are gold and silver mines as well as a 300 km² primary-forest logging concession.

Olalla brothers’s titi monkey (Plecturocebus olallae) – Bolivia – < 3,000 animals

With a total population of at most 2,855 individuals, the Beni titi monkey lives exclusively in a small, naturally fragmented forest mosaic on the upper Río Yacuma in Bolivia’s Beni Department. The habitat is massively threatened by livestock grazing, fire, road building and settlement expansion. Slash-and-burn burning to rejuvenate pastures in particular leads to forest loss and smoke pollution. As a result, family groups lose their territory or are forced into risky movements on the ground. A planned paved road (Northern Corridor) further increases land-use pressure.

Despite these threats, there is also hope: two community protected areas (“Pampas del Yacuma” and “Rhukanrhuka”) now protect around 90 % of the known range. Environmental education, monitoring and cooperation with ranchers support conservation. Nevertheless, according to the IUCN the Olalla brothers’s titi monkey is endangered – long-term protection is only possible with ecologically adapted regional management.

Barbara Brown’s titi monkey (Callicebus barbarabrownae) – Brazil (Bahia & Sergipe) – < 500 adult animals

The species is endemic to Brazil’s Caatinga dry savanna and is considered endangered. It lives exclusively in small forest remnants that are heavily fragmented by livestock grazing, agriculture and urbanization. Its overall range covers around 291,000 km², but the actually usable habitat has shrunk to less than 2,700 km² – only 1 % of that is protected. A recent count found around 400 adult animals in 194 groups across 92 sites. However, newer data also show local extinctions as a result of slash-and-burn clearing, mining and selective logging. Increasing dryness, urbanization (+67 % in just ten years) and climate change further worsen the situation.

Pied tamarin (Saguinus bicolor) – Brazil – <1,000 animals

The pied tamarin lives exclusively in the area around the Brazilian metropolis of Manaus and is increasingly confined there to small, isolated forest fragments – sometimes only a few hectares in size. In some parks, only individual groups of five to 15 animals remain. Even in the 10,000 ha Ducke Reserve, only about 620 individuals could be counted.

The species is endangered: a decline of at least 80 % is expected over the next 18 years. Main causes are logging, habitat fragmentation, road building, competition with the golden-handed tamarin (Saguinus midas), illegal pet keeping, as well as high losses due to dogs, cats, diseases and power lines.

Central American squirrel monkey (Saimiri oerstedii) – Costa Rica & Panama – ≤ 5,000 animals

The Central American squirrel monkey is divided into two subspecies: S. o. oerstedii in southwestern Costa Rica and adjacent parts of Panama, and S. o. citrinellus in Costa Rica’s central Pacific lowlands. For both populations, a decline of at least 50 % over the last three generations is assumed – due to an approximately 60 % reduction in their range.

Current estimates assume a total of fewer than 5,000 individuals. In some regions, such as the southern La-Amistad National Park, 54 groups with 1,638 animals were recorded. Especially outside protected areas, the animals are increasingly threatened. Main threats: deforestation for agriculture (especially oil palm, teak, bananas), habitat fragmentation, power lines (electrocution), road traffic, attacks by dogs, and illegal pet trade. Even in protected areas, continuous tree corridors are often missing – particularly serious for these small, strictly arboreal monkeys.

Yellow-tailed woolly monkey (Lagothrix flavicauda) – Peru – 1,000–10,000 animals

The yellow-tailed woolly monkey lives in the moist montane cloud forests of northern Peru. Current estimates vary widely, but there are probably only between 1,000 and 10,000 individuals left. The animals occur at very low densities (usually under two groups/km²) and require large, contiguous forest areas.

Up until the 1950s, the inaccessibility of its habitat largely protected the species. Since then, road building, selective logging, mining and hunting have led to massive losses. Between 1981 and 2008, suitable habitat declined by almost half – from 11,240 to 6,300 km². If the current pace continues, by 2030 almost all unprotected forests could be lost. In addition, the species is heavily hunted – both for meat and because juveniles are sold as pets when their mothers are shot. Conflicts over alleged crop damage also lead to killing.

Brown spider monkey (Ateles hybridus) – Colombia/Venezuela – likely decline of >80 % over three generations

The brown spider monkey is among the most endangered primates in South America. Less than 20 % of its original range remains in Colombia; in Venezuela the situation is similarly precarious. Large, contiguous forests exist only in a few regions such as the Serranía de San Lucas and the Perijá Mountains – but even there, the species is heavily hunted, partly for meat and partly for traditional medicine or the pet trade.

A decline of more than 80 % within three generations (2018–2063) is considered very likely. Studies show that in intensively hunted areas, populations of Ateles species can collapse severely. Habitat is also shrinking rapidly – due to cattle ranching, illegal clearing, road building and new settlements. In protected areas, protection is often insufficient: buffer zones are cleared, primary forest disappears. Observations suggest that many former occurrences have already vanished today. The remaining populations live in highly fragmented habitats and are isolated and genetically at risk.

Protection needs data, people and political will

Despite the alarming figures, there is hope. In many regions, conservation measures are being implemented: reforestation, education programs, participatory protected areas, resettlement projects and increased patrols. But the success of these measures depends crucially on political will, the involvement of local communities and international support.

The IUCN report clearly calls for protecting critical habitats more consistently, involving Indigenous communities and strengthening legal frameworks against wildlife trafficking and illegal clearing. It also calls for long-term, well-funded conservation programs and monitoring to detect ecological changes in time and counteract them.

The loss of every single primate species not only means an irreversible cut in biological diversity but can also have far-reaching consequences for humans. Many of these species perform key ecological functions as so-called keystone species. When such species disappear, the corresponding ecosystems become unbalanced and can change permanently.

---

The new list of the 25 most endangered primates makes one thing clear: numerous species are on the brink of extinction – many of them are highly specialized, occur only in tiny regions or have only recently been scientifically described. Habitat loss, poaching, the climate crisis and political instability threaten these animals on multiple levels at once. Despite individual successes and dedicated conservation projects, the challenges are immense – and the remaining time is short.

But there is hope: conservation measures work when they are designed for the long term, well funded and locally anchored. What matters is that political decision-makers, scientists, NGOs and local communities act together. Every primate species that disappears leaves not only an ecological gap – its loss also symbolizes the failure of global species conservation.

Source

• Mittermeier, R.A., Reuter, K.E., Rylands, A.B., Ang, A., Jerusalinsky, L., Nash, S.D., Schwitzer, C., Ratsimbazafy, J. & Humle, T. (Eds.). (2024). Primates in Peril: The World’s 25 Most Endangered Primates 2023–2025. IUCN SSC Primate Specialist Group, International Primatological Society, Re:wild, Washington, DC.