- The latest list of the 25 most endangered primates includes nine from Asia, six from the Americas, six from the African mainland, and four from Madagascar.
- Madagascar is home to 112 known lemur species, nearly all of which face the threat of extinction or what they report calls “collective endangerment,” where entire taxonomical groups are at risk of dying out.
- Several primates feature on the list for the first time, including the Sahafary sportive lemur, red-bellied monkey, northern pygmy slow loris, Myanmar snub-nosed monkey, Central American squirrel monkey, and Bornean banded langur.
- The report is also designed to spur conservation efforts for the listed species, as happened in the case of Brazil’s pied tamarin, a species for which the Brazilian government created a strict reserve in 2024.
Nearly two-thirds of all primates are in danger of disappearing, including 100 that have only been described by science in the last 25 years. To spotlight their plight, leading conservation organizations compiled a list of 25 of the most endangered primates in the latest edition of the “Primates in Peril” report.
“Since its inception 25 years ago, the Top 25 list has made a significant contribution to primate conservation, highlighting those species in greatest need and often stimulating major conservation measures such as the creation of new protected areas and increased funding for the target species,” said Russell Mittermeier, a renowned U.S. primatologist who heads the Primate Specialist Group at the IUCN, the global wildlife conservation authority.
While many in the order, which includes everything from great apes like gorillas and chimpanzees, to monkeys, lemurs, bush babies and humans, face dire conditions, the selection of the top 25 is purposeful, scientists involved in the report, told Mongabay. It is not a strict ranking based on the severity of threats species face but also aims to be representative of the different geographic regions where primates live and the wide diversity within the primate order.
“We also try to select species where inclusion is actually going to be helpful” and spur conservation efforts, Mittermeier said.
The new report is a collaboration between the IUCN, the International Primatological Society, and the nonprofit Re:wild. Mittermeier is also the chief conservation officer at Re:wild.
The latest list includes nine primates from Asia, six from the neotropics (tropical areas of the Americas), another six from the African mainland, and four from Madagascar.
Mittermeier, a leading authority on Madagascar’s lemurs, spoke to Mongabay from western Madagascar, home to the critically endangered Madame Berthe’s mouse lemur (Microcebus berthae). “It’s the smallest primate in the world and it’s in a lot of trouble. It is one of the two or three highest-priority species,” he said.
Madagascar is considered a separate region from the African mainland because of its tremendous biodiversity and high rates of endemism. The island nation is home to 112 known lemur species, nearly all of which face the threat of extinction or what the report calls “collective endangerment,” where entire taxonomical groups are at risk of dying out.
Another group of concern is the great apes: chimpanzees, bonobos, gorillas and orangutans. Humans are also considered great apes, but have never been featured on the list.
Among the 25 primates in the latest edition of the list, the report highlights the risk to five in particular, including the Cross River gorilla (Gorilla gorilla diehli).
Despite being vanishingly rare, there is a glimmer of hope for these gorillas, according to Inaoyom Imong a Nigerian conservation biologist.
“The Cross River gorillas occur in Nigeria and in Cameroon,” said Imong, director of the Cross River Gorilla Landscape Project at the NGO Wildlife Conservation Society. “[O]n the Nigerian side, the situation is actually improving, at least in terms of hunting and poaching pressure.”
In Cameroon, however, civil unrest and the presence of armed groups inside the forested areas where the gorillas live is putting them at greater risk, Imong told Mongabay.
Cross River gorillas have appeared on the 25 most endangered primates list five times previously; their last inclusion was in 2008. Imong said he hopes the listing will bring renewed attention and funding to protect this rare gorilla subspecies. Only 250 mature Cross River gorillas are thought to remain in the wild.
Another great ape on the list with an alarmingly small population size is the Tapanuli orangutan (Pongo tapanuliensis), found only in the Batang Toru Forest in Sumatra, Indonesia. Scientists first recognized it as a distinct species in 2017, and it has already been featured twice on the list: in 2018 and 2022. Its entire population is estimated at just 800.
Several other primates feature on the list for the first time: the Sahafary sportive lemur (Lepilemur septentrionalis), red-bellied monkey (Cercopithecus erythrogaster), northern pygmy slow loris (Xanthonycticebus intermedius), Myanmar snub-nosed monkey (Rhinopithecus strykeri), Central American squirrel monkey (Saimiri oerstedii), and Bornean banded langur (Presbytis chrysomelas).
Vincent Nijman, a primatologist at Oxford Brookes University in the U.K., who specializes in the study of Southeast Asian primates, said he hopes the listing will bring greater attention to the reclusive Bornean banded langur. These leaf-eating monkeys are found only in hard-to-access swampy woodlands in Borneo. The island, shared between Indonesia, Malaysia and Brunei, is a primate hotspot, especially for langurs.
P. chrysomelas was once very common across this region, but today a few hundred members of the species occupy less than 5% of its historical range. The expansion of cash crop cultivation, land-use changes and forest fires have all eaten into the langur’s habitat.
The dry forest of western Madagascar, the only known home of the Madame Berthe mouse lemur, is also shrinking rapidly.
“Primates are 90% tropical rainforest species,” Mittermeier said. “Tropical rainforests are under the gun in most of the world. The overarching problem is habitat destruction.” The report also cited hunting, bushmeat consumption, trade in wild animals, and diseases as major threats.
Habitats are also being lost to the growing urban footprint of another primate: Homo sapiens. That’s the case for the striking-looking pied tamarin (Saguinus bicolor), a species with a tiny distribution living in the shadow of a major human settlement: the Brazilian city of Manaus. Including the pied tamarin in the top 25 list was a strategic decision, according to Leandro Jerusalinsky, who heads the National Center for Research and Conservation of Brazilian Primates.
Jerusalinsky, who is also the deputy chair of the IUCN’s Primate Specialist Group, said he considers the list “an amazing tool to promote the awareness about the species and to make outreach to the institutions, to enterprises, to governments and to society.”
His experience has borne this out. The 2025 report is a product of the efforts of a global network of scientists who compile the documentation about each species over two years. The list itself was drawn up at a meeting held in August 2023 in Sarawak, Malaysia, during the 29th Congress of the International Primatological Society.
One item on almost every primatologist’s wish list is creating sanctuaries for these rare animals in areas where they still persist. A spot on the most endangered list helped to make that a reality for the pied tamarin: In 2024, the Brazilian government created the Pied Tamarin Wildlife Refuge, a strict reserve.
However, the listing does more than grab the attention of decision-makers; it can also influence fellow scientists, especially the fresh crop of primatologists.
“The attention translates, not just from this report, but in general, to people wanting to protect them, people wanting to raise funds for them, to people wanting to study them,” Nijman said.
He cited the experience of his own department at Oxford Brookes University which offers a master’s degree course in primate conservation. “We’ve looked at how many students focus on the top 25 species over the years, before they became a top 25 species and then subsequently. And we see a change,” he said. “Students are more likely to pick up a species after it’s been put on this list.”
Banner image: Madame Berthe’s mouse lemur (Microcebus berthae) is endemic to Madagascar. Image courtesy of Matthias Markolf.
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