Expedition Discovers 27 New Species in Peru, From an ‘Exceedingly Rare’ Amphibious Mouse to a Blob-Headed Fish

Between the Andes Mountains and the Amazon, a verdant pocket of land known as Alto Mayo supports roughly 280,000 people—but despite decades of human encroachment and deforestation, scientists have discovered it also hosts a staggering level of biodiversity.

In June and July 2022, researchers led by the nonprofit Conservation International made a 38-day expedition to the Alto Mayo region of Peru and uncovered 27 new species. The previously unknown creatures include four mammals, eight fish, three amphibians and ten butterflies, the team writes in a 474-page report published Friday.

In a region with high human population density—with settlements dotted between scribbles of rivers and towers of forested mountains—these finds were unexpected.

“People had been operating under the assumption that with so much human influence, there wouldn’t be very high biodiversity,” Trond Larsen, senior director for biodiversity and ecosystem science at Conservation International, explains to Annie Roth of the New York Times. “But we found the exact opposite.”

Among the most surprising new finds were an “exceedingly rare amphibious mouse,” a “narrow-mouthed frog” and a “bizarre ‘blob-headed’ fish for which the function of its unusual head remains a mystery,” according to a statement from Conservation International.

The discovery of the amphibious mouse with webbed feet was particularly “shocking and exciting,” Larsen tells Graeme Green of the Guardian.

“It belongs to a group of carnivorous, semi-aquatic rodents, for which the majority of species are exceedingly rare and difficult to collect, giving them an almost mythical status among mammal experts,” he adds. “We only found this amphibious mouse in a single unique patch of swamp forest that’s threatened by encroaching agriculture, and it may not live anywhere else.”

But the other findings are also unusual. The “blob-headed fish” is technically a bristlemouth armored catfish with a bulbous nose—and it is, by all accounts, strange. Prosanta Chakrabarty, an ichthyologist at Louisiana State University who was not part of the expedition, speculates that the nose might have a role in sensing underwater prey, though its function remains a mystery.

The presence of “weirdos” like this catfish, he tells the New York Times, “goes to show you how many fish species there still are to discover.”

In total, the expedition recorded 2,046 species, 49 of which are listed as threatened by the International Union for Conservation of Nature and at least 34 of which appear to live only in Alto Mayo and its surrounding San Martin region. Among the rarest finds were two critically endangered primates: the Peruvian yellow-tailed woolly monkey and the San Martin titi monkey.

“There’s a lot of agriculture and land conversion going on in the area,” Reynaldo Linares-Palomino, a tropical biologist at the Smithsonian’s National Zoo and Conservation Biology Institute who was not part of the expedition, tells the New York Times. “Despite that, this team still managed to document new species, which is exciting.”

But, Linares-Palomino adds, “the existing conservation initiatives are not enough.”

In recent years, Alto Mayo has made the news as the site of controversial conservation work. When companies buy carbon credits to offset their emissions, their money often goes to green initiatives like reforestation. Disney, for instance, spent about 40 percent of its carbon offsets between 2012 and 2020 in Alto Mayo, “in theory cancelling out rising emissions from cruise ships and theme parks,” Patrick Greenfield reported for the Guardian in 2023.

From one perspective, Alto Mayo was a success story, with corporate-funded conservation efforts stopping more than 8,000 acres of forest from disappearing during that time period, according to the Guardian.

But this model of conservation can reportedly come at a cost to humans in the relatively densely populated region. In some cases, residents, often poor, smallholder farmers, are asked to sign voluntary conservation agreements regulating their land use. In other cases, residents told the publication they had been forced off their land by authorities.

“They told us to get our things ready and leave,” Abel Carrasco, a 39-year-old coffee farmer whose house was demolished in 2021, told the Guardian. “They said it’s a protected forest, nobody can be here.”

Some residents express frustration that international corporations, nonprofits and the Peruvian state are letting the cost of conservation fall on some of the country’s most vulnerable populations.

“They build the roads, and then they get mad when people come here,” Jose Gilmer Vasquez, an Alto Mayo resident who unwittingly moved into the protected region in the 1990s, told Blanca Begert for Sapiens in 2021. “Where are we supposed to go?”

Conservation International acknowledges that the livelihoods of Alto Mayo’s residents can unintentionally rely on land-use practices that run counter to the best interests of the rare species in the region. Around the turn of the 21st century, many local people rented land to migrant farmers to earn a living, leading to deforestation.

“Communities didn’t deforest their land because they wanted to—it was out of necessity,” Diego Dourojeanni, who leads Conservation International’s work with the Indigenous peoples of the Alto Mayo, says in another statement. “While it helped in the short term, it became clear that this practice came at a steep cost to resources, food security and the ecosystem services like clean water that the forests provide.”

In these conditions, landscape restoration and conservation initiatives become ethically and politically fraught, and questions around how the land should be managed are complex. But efforts like the 2022 expedition, the team argues, show that the region is not yet a lost cause—and that it has many further natural wonders that can still be saved.

“We need to keep documenting the diversity of organisms around us if we want to understand what is happening and the best ways to manage our environment,” Linares-Palomino tells the New York Times.

Dourojeanni points out that “it’s really, really hard to compete with agricultural drivers of deforestation.” But he remains optimistic that communities will value the forest and its biological riches for more “emotional” reasons, rather than “just for income’s sake.”

“It’s not too late yet,” he says in the statement. “If we do the right thing, people and nature can co-exist on this landscape.”