Two New Howler Monkey Species Found in the Amazon After 84 Years
Two monkeys lived in the Amazon for hundreds of thousands of years before anyone gave them a scientific name. On October 30, 2026, a team led from Brazil and the UK described them in the journal Communications Biology: the Pantepui red howler and the Mato Grosso red howler. The University of Salford, home of the senior author, says they are the first new howler monkey species described in 84 years.
Lead author Romina Batista of the National Institute of Amazonian Research (INPA) in Manaus and senior author Jean P. Boubli of Salford headed a paper with 41 authors. They used genome-wide data, DNA markers read from across the whole genome instead of one or two genes, covering 11 of the 13 howler species recognised at the time. BioExplorer, which reviewed the paper, reports the main analysis drew on 83 monkeys and nearly 2,000 genetic markers. The team then checked the genetic groups against fur patterns and other physical traits in museum specimens.
The count changes too. According to the German science site wissenschaft.de, the genus had 13 species and 3 subspecies before the study. The authors now propose 16 species and 2 subspecies, because one former subspecies moves up to full species alongside the two new ones. Taxonomic databases have not yet reviewed the revision.
Two monkeys, two ranges
The Pantepui red howler, A. iroi, lives in northwestern Brazil between the Rio Branco and the Rio Cauaburi, north of the Rio Negro. Its range likely reaches north into the Pantepui, the region of tabletop mountains called tepuis. The name comes from iro, the Yanomami word for howler monkey. Its closest relative is the Guyanan red howler. The two split about 700,000 years ago, the most recent split in the howler family tree, and the authors suspect the Rio Branco kept them apart.
The Mato Grosso red howler, A. matogrossensis, lives in the southern Brazilian Amazon, from the east bank of the Rio Madeira to the west bank of the Rio Teles Pires, with the Rio Guaporé at its southwestern edge. Open savanna separates it from its closest relative, the Bolivian red howler. National Geographic reports the researchers estimate it has been its own species for more than half a million years.
How rivers split one species into several
The Salford release says big rivers such as the Amazon, Rio Branco and Xingu have worked as barriers for millions of years, so populations on opposite banks evolved apart. What scientists had counted as one species held several separate lineages. Howlers can swim. As BioExplorer reports Batista's point, a river does not have to stop every crossing to slow the flow of genes between its banks.
One of the new species is already at risk
The Mato Grosso red howler lives inside the Arc of Deforestation, the southern rim of the Brazilian Amazon where forest loss runs highest. Batista ties that loss mainly to farm monocultures, cattle ranching and growing towns. The authors write that the species is likely to qualify as Critically Endangered, the most severe threat category on the International Union for Conservation of Nature (IUCN) Red List short of extinction in the wild. It also had the lowest genome-wide heterozygosity, a measure of genetic variety, of any howler lineage sampled. The IUCN has not assessed it yet.
Boubli told National Geographic he believes the species is either endangered or critically endangered, judging by the state of its forest. The genus was in trouble before this paper: its abstract says 11 of the 16 howler species and subspecies recognised before the study are listed as threatened. "Understanding the different species in existence is the first step towards protecting them," Batista said in the Salford release.
A name gives conservation a target
A species without a name cannot go on a threatened list or into a protection plan. Boubli says he hopes the findings help conservation groups find the populations most at risk and set protection priorities across the Amazon Basin. The Mato Grosso red howler now has a mapped range, a type specimen and a case for a formal IUCN assessment.
Help on the ground already exists. Projeto Reconecta, led by road ecologist Fernanda Abra, strings rope bridges over roads so tree-dwelling animals can cross without coming down to traffic. A camera on one bridge in Alta Floresta, a growing town in Mato Grosso, photographed a Mato Grosso red howler using it.
📍 Multiple Perspectives on the Story
Specimens that waited years for a name
The type specimens, the individuals that formally define each species, were collected long before the paper, BioExplorer reports. The Pantepui red howler's is an adult male taken in 2005 at the foot of the Serra do Aracá in Amazonas state. The Mato Grosso red howler's is a female taken in 2014 on the Rio Teles Pires near Alta Floresta. The same analysis redraws the older branches of the family tree too, dating the split between Central and South American howlers to about 3.5 million years ago.
One road crossing, three recently named monkeys
Abra told National Geographic the Reconecta bridges now serve three monkeys described in recent years: the Critically Endangered Alta Floresta titi monkey, named in 2019, Schneider's marmoset, named in 2021, and the new howler. Cameras on the bridges also record capuchins and other marmosets and titis. National Geographic says the bridges appear to prevent roadkill but gives no figures, so the size of that effect is not public yet.
The other new species has its own threats
Most coverage has focused on the Mato Grosso red howler. BioExplorer reports the authors also flag risks for the Pantepui red howler: a planned dam on the Rio Branco, the same river that likely separates it from its closest relative, and projected climate change. No population estimate exists for it either.
A name is not protection
The paper names two species. It protects none. No new protected area came with it, and the Critically Endangered label is the authors' expectation, not an IUCN ruling. The 16-species count is a proposal that taxonomic databases still have to accept. The "84 years" figure matches 1941 to 2025, the year the paper was submitted; by its 2026 publication the gap was 85.
Fieldwork that depended on local help
In the paper's acknowledgments, Boubli thanks the Yanomami people and the ribeirinho (riverside) communities of the Rio Negro Basin for their help during surveys, along with Catholic and Evangelical missionaries who supported the team at remote outposts. The Rio Branco and the Rio Cauaburi, the two rivers that bound the Pantepui red howler's range, both feed the Rio Negro.
What to watch next
The IUCN assessment of the Mato Grosso red howler will put the authors' warning on the formal record, or revise it. Field surveys still need to count both species, since none of the reporting gives a population figure for either. Land decisions between the Madeira and Teles Pires rivers, and on the planned Rio Branco dam, will decide how much forest each species keeps. Meanwhile the Reconecta cameras in Alta Floresta keep recording which animals cross.
Frequently Asked Questions
What are the two new howler monkey species?
The Pantepui red howler (Alouatta iroi) lives in northwestern Brazil, north of the Rio Negro between the Rio Branco and the Rio Cauaburi. The Mato Grosso red howler (Alouatta matogrossensis) lives in the southern Brazilian Amazon between the Rio Madeira and the Rio Teles Pires. Both were described in Communications Biology on October 30, 2026.
Why did it take so long to recognise them?
Scientists had grouped each of them with close relatives. Genome-wide DNA from 11 of the 13 recognised howler species showed separate lineages, split by rivers and savanna, and museum specimens backed up the split. The University of Salford says the last new howler species was described in 1941.
Is the Mato Grosso red howler endangered?
The IUCN has not formally assessed it. The study authors expect it to qualify as Critically Endangered because its range lies inside the Arc of Deforestation in southern Amazonia, and senior author Jean Boubli told National Geographic it is either endangered or critically endangered.
How many howler monkey species are there now?
The authors propose 16 howler species and 2 subspecies, up from 13 species and 3 subspecies, because one subspecies moves up to full species besides the two new ones. Taxonomic databases have not yet reviewed the revision.