Two newly recognized howler monkey species have been discovered in the Amazon rainforest, marking the first identification of a new howler species in 85 years. Scientists described the moment as a "critical call for the conservation of threatened Brazilian ecosystems."

The discovery followed the first genome wide study of the genus Alouatta, better known as howler monkeys. These noisy primates live across Central and South America and are famous for their unmistakable hoots, roars, and barks.

Howler monkeys are considered the loudest land animals in the world. Their guttural calls can be heard from as far as 5 kilometers (3 miles) away and are used to discourage rivals, mark territory, and communicate without violence.

Scientists led by Dr Romina Batista and Professor Jean Boubli of the University of Salford gathered genetic evidence from 86 howler monkeys across the animals’ range. The research included material taken from museum specimens.

One DNA sample came from pieces of dried skin found on two mounted specimens at the Zoologische Staatssammlung München, also known as the Bavarian State Collection of Zoology in Munich. Such samples contributed to a broad examination of howler monkey genomes.

The analysis confirmed suspicions held by many biologists that the howler monkey family tree is unusually complex and requires substantial revision. Most notably, the genetic evidence revealed two species that had not previously been formally recognized.

The first is Alouatta iroi, also called the Pantepui red howler. It inhabits the northwestern Amazon between the Rio Branco and Rio Cauaburi and can be recognized by its bright yellowish brown to golden coat.

The second is Alouatta matogrossensis, also known as the Mato Grosso red howler. This separate species lives in southern Amazonia between the Rio Madeira and Rio Teles Pires and has a bright reddish brown coat.

"Our study shows that the Amazon still holds remarkable biological secrets, even among well-known animals such as howler monkeys," Dr Romina Batista said in a statement. The findings show how genetic research can reveal hidden distinctions even among familiar animals.

Beyond identifying the two new species, the paper proposes a wider reconsideration of how several other howler monkeys are classified. The evidence indicates that A. puruensis is not a valid species and is instead the same species as A. juara.

The researchers also support the possibility that the Trinidad howler, A. insulanus, is a distinct species rather than merely a subspecies. However, nuclear DNA is still required to confirm that proposed classification.

By examining the monkeys’ genes, the researchers also developed a detailed picture of their evolutionary history. Their findings suggest the Alouatta genus most likely originated in Mesoamerica before spreading south into South America.

The earliest divergences within the genus occurred around 3.5 million years ago, separating Central American and South American howlers. That timing roughly corresponds with the formation of the Panama land bridge.

Additional species emerged as major rivers developed across the region. Rivers including the Amazon blocked gene flow between populations, allowing separated groups to follow distinct evolutionary paths over time.

Other geographical changes in the basin also encouraged speciation. The formation of savannas in parts of the Amazon Basin divided the ranges of A. nigerrima and A. sara, contributing to further separation.

Researchers say the discoveries carry urgent conservation importance as deforestation, climate change, and habitat loss threaten Amazonian animals before they have been fully understood or discovered by science. "We hope these findings will help conservation organisations identify the most vulnerable populations and prioritise protection efforts across the Amazon Basin," Professor Jean Boubli said.

A more precise understanding of the genus and its genetic diversity could help conservation organizations fine tune their work and determine which populations most need protection. The study was published in the journal Communications Biology.