Blob-headed fish and amphibious mouse among 27 new species found in ‘thrilling’ Peru expedition

Scientists surprised to find so many animals unknown to science in Alto Mayo, a well-populated region

The expedition was “thrilling to be part of”, said Dr Trond Larsen, senior director of biodiversity and ecosystem science at Conservation International’s Moore Centre for Science,

Researchers in the Alto Mayo region of north-west Peru have discovered 27 species that are new to science, including a rare amphibious mouse, a tree-climbing salamander and an unusual “blob-headed fish”. The 38-day survey recorded more than 2,000 species of wildlife and plants.

The findings are surprising given the region’s high human population density, with pressures including deforestation and agriculture.

The expedition was “thrilling to be part of”, said Dr Trond Larsen, senior director of biodiversity and ecosystem science at Conservation International’s Moore Centre for Science, who led the survey.

“The Alto Mayo landscape supports 280,000 people in cities, towns and communities. 

With a long history of land-use change and environmental degradation, I was very surprised to find such high overall species richness, including so many new, rare and threatened species, many of which may be found nowhere else.” 

The “new” species include four mammals: a spiny mouse, a short-tailed fruit bat, a dwarf squirrel and the semi-aquatic mouse. 

Discovering a new species of amphibious mouse was “shocking and exciting”, Larsen said. 

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.

"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.” 

The dwarf squirrel is about 14cm long and fast-moving, making it extremely difficult to spot in the dense rainforest.

Larsen was particularly satisfied to find a new arboreal salamander “with stubby little legs and mottled chestnut-brown colouration, climbing at chest height in a small patch of white sand forest”. But the most intriguing find was “the blob-headed fish, which looks similar to related catfish species but with a truly bizarre speckled blob-like extension on the end of its head”, Larsen said. 

A new species of ‘blob-headed’ fish. The function of their unusual structure remains a mystery. Picture: Robinson Olivera.

“The function of this ‘blob’ remains a complete mystery. 

If I had to speculate, I might guess it could have something to do with sensory organs in the head, or it may assist with buoyancy control, provide fat reserves or aid in its foraging strategy.” 

Seven other new types of fish were also documented, along with a new species of narrow-mouthed frog, 10 new butterflies and two new dung beetles. Another 48 species that were found may also be new to science, with analysis under way to confirm.

The expedition also documented 49 “threatened” species from the IUCN’s red list , including two critically endangered monkeys (the Peruvian yellow-tailed woolly monkey and San Martin titi monkey ), two endangered birds (the speckle-chested piculet and long-whiskered owlet ) and an endangered harlequin frog.

The survey was conducted in June and July 2022, using camera traps, bioacoustics sensors and environmental DNA (eDNA) collected from rivers and other water sources. The team of 13 scientists included Peruvian scientists from Global Earth, as well as seven technical assistants with extensive traditional knowledge from Feriaam (the Indigenous Regional Federation of the Alto Mayo Awajún Communities).

Of the 2,046 total species recorded, at least 34 appear to live only in the Alto Mayo landscape or the San Martin region it falls in.

While the species have never been described by science (the process of assigning a species and name), some were already known to Indigenous communities. “As Awajún people, we have a great deal of knowledge about our territory,” said Yulisa Tuwi, who assisted with the research on reptiles and amphibians. 

We know the value of our plants, how they cure us, how they feed us and we know paths within the forest that have led us to meet different animals.

“Although we don’t know scientific names, we’ve developed a classification of these species … I believe the discoveries are for the scientific world, not so much for us, as these species are known under other names or for their usefulness or behaviour in nature.”

Researchers hope the survey will bolster conservation efforts, including plans to create a network of local protected areas.