A total of 27 new species have been uncovered in the ‘human-dominated’ Peruvian rainforest.

Conservation International led the expedition into the Alto Mayo Landscape that discovered these new species. The list includes four mammals, eight fish, three amphibians and 10 butterfly species.

The team was joined in the field by Peruvian scientists from Global Earth and local experts with extensive traditional knowledge from the Indigenous Regional Federation of the Alto Mayo Awajun Communities.

“Discovering even one new species of mammal on an expedition would be extraordinary, but discovering four new mammal species, as well as eight new fishes and three new amphibians, is mind-blowing,” says Trond Larsen, who leads Conservation International’s Rapid Assessment Program (RAP).

What did researchers find in the Peruvian rainforest?

Once the 2024 fieldwork was complete, months of complex data analyses followed to confirm the discovery of new species and come up with conservation plans for them, explains Larsen.

Researchers found 151 mammals in total, four of them new to science, including a bat, a squirrel, and a spiny mouse. At least 12 of these species are threatened with extinction.

The team also found 68 fish species – with eight new to science – including a fish with a blob head that they don’t yet know the purpose of and that Larsen is “most excited” about, given his personal passion for aquatic creatures.

“It is truly exciting and amazing to encounter a species such as the blob-headed fish that is so bizarre and distinct, yet has never before been seen by scientists,” he says. “It’s fun to speculate and try to understand why this fish species possesses such an unusual structure on its head”.

Larsen is also “exhilarated” by the discovery of an incredibly rare amphibious mouse.

“This new species belongs to a group of semi-aquatic carnivorous rodents that are notoriously rare and difficult to encounter in the field,” he says.

The researchers also found 45 reptile and amphibian species, with three new to science: a rain frog, a narrow-mouthed frog, and a climbing salamander.

12 insects new to science were among the 289 they recorded in total. That is alongside 536 bird species and 955 plant species – including rare orchids and other flora only found in this area.

This ‘blob-headed’ fish (Chaetostoma sp.), is also new to science and was a shocking discovery due to its enlarged blob-like head. © Conservation International/photo by Robinson Olivera

Another 48 species of plants and animals observed during the expedition may also be new to science but require further research before this can be confirmed.

Of the incredible 2,046 different species researchers recorded, at least 34 of them appear to live only in the Alto Mayo Landscape of Peru’s San Martin region.

There are life-threatening risks associated with tropical expeditions

The team didn’t just use traditional methods for surveying plants and animals. They deployed technologies such as automated camera traps, bioacoustic sensors and environmental DNA (eDNA) to identify animals based on DNA they have shed into the water, explains Larsen.

“This expedition was probably the most complex and large-scale RAP we have ever done,” he adds. “The researchers worked non-stop and with little rest to achieve this massive task.”

Larsen, however, says that living in a tent in the tropical rainforest “feels like home.”

Fieldwork in remote tropical places around the world can pose many risks to health.

While Larsen emerged unscathed from this latest Alto Mayo RAP expedition, he’s previously picked up “a variety of diseases and parasites, including malaria, leishmaniasis (a flesh-eating disease), creeping eruption (parasitic worms that form inflamed tunnels as they burrow around just under the skin), botfly maggots that embed themselves into flesh and poke in and out of a breathing hole, and a multitude of intestinal parasites”.

He also now is “deathly allergic” to red meat and dairy after thousands of tick bites gave him a condition called alpha gal syndrome.

How are names selected for new species?

If a species is new to science, then it won’t yet have a common name.

“Researchers choose one based on the discovery’s most distinctive and unusual features,” explains Larsen, as is the case with the blob-headed fish. But also, he says, “common names can refer to the group of species to which the animal belongs, such as the mushroom-tongued salamander, for which other species in the same genus also share a similar yet distinctive tongue.”

Sometimes scientists give a name to other respected field researchers – and Larsen knows a thing or two about this, given that he has 10 beetles named after him.

“I feel grateful and humbled to be recognised and honoured by fellow scientists who have chosen to reward my hard work, dedication and passion for tropical ecology by naming species I have discovered after me.”

“The opportunity to explore new places and immerse myself in nature, discovering and learning more about the incredible diversity of life, is really what drives me and makes me feel happiest.”

Can nature coexist with humans?

The Alto Mayo Landscape is a region with incredible biodiversity despite its relatively high population density. The presence of humans has put major pressure on the local environment from deforestation and agricultural expansion.

But Conservation International has been working with Indigenous groups in the region, such as the Awajún people, as well as local communities and governments to support sustainable livelihoods and agricultural practices that balance the needs of people and nature in the region.

Members of the insect team survey a swamp forest using nets and various types of traps. © Trond Larsen

“The tremendous discoveries and unique biodiversity we found on the Alto Mayo RAP expedition are a testament to the fact that biodiversity can thrive alongside people,” says Larsen.

“These findings underscore that even in areas heavily influenced by people, biodiversity can persist but only if ecosystems are managed sustainably.”

Data from this expedition will help inform plans to connect the Alto Mayo Protected Forest with the Cordillera Escalera Regional Conservation Area and create an ecological corridor that will help species survive.

It will also help local communities to better protect the nature that surrounds them.

“This Rapid Assessment allows the Awajún to protect our culture, natural resources and our territory, as we have a deep connection with nature,” says Yulisa Tuwi, an Awajún woman who assisted with the research on reptiles and amphibians.

“Being part of this research has allowed me to better understand how plants, animals and ecosystems interact with each other, and how this is part of our Awajún cosmovision.”