Two new species of aquatic mice discovered in the Congo

A pair of newly discovered aquatic mice species – with elongated feet and water resistant fur – are amongst the ‘world’s rarest mammals’, a new study found.

Researchers from the Field Museum, Chicago, say the mice are native to the remote Congo basin and evaded scientific detection due to political unrest in the area. 

The two species, previously unknown to science, are related to a mouse known as ‘Nilopegamys’ – or mouse from the source of the Nile found 93 years ago in ethiopia.

The new mice are cousins of that species – now believed to be extinct – and are both types of a ‘Colomy’ or stilt mouse – found in the Congo Basin and western Africa.

‘Stilt mice’ feast on water-dwelling insects in swamps, streams and rivers and use their whiskers on the water’s surface to detect movements of insects – like sonar. 

An illustration of one of the newly-described species of stilt mouse, Colomys lumumbai, wading in a stream to hunt

Ninety-three years ago, a scientist trapped a mouse in a stream in Ethiopia and it stood out as one of the most adapted for living in water – the specimen is the only known member of a species dubbed Nilopegamys – housed in the Field Museum. 

Nilopegamys is believed to be extinct but the two new Colomy species of mouse are thought to be its closest living relatives. 

Study author Dr Julian Kerbis Peterhans said the two species of mouse had been confused with one another since Nilopegamys was first discovered.

They are both ‘remarkably similar’ in how well adapted they are to living in water.  

The elusive mammals have unusually large brains to process this sensory information from their whiskers when they hunt, according to Dr Kerbis Peterhans, who has studied aquatic rodents for over three decades.

They’re cute, too, added Peterhans, saying when he caught his first member of the Colomy family 30 years ago it was the ‘most beautiful African mouse’ he’d ever seen. 

They’re soft, and they have this remarkable snow-white belly,’ said Kerbis Peterhans.

Due to the fact they live in the water – and can go out to areas up to four feet deep – they are remarkably hard to catch, according to the team. 

‘They’ve been so elusive for so long, they’re some of the rarest animals in the world, so it’s exciting to finally figure out their family tree,’ Kerbis Peterhans said.

Lead researcher Dr Tom Giarla, at Siena College in New York, added that very little is known about biodiversity of small animals, particularly in the tropics. 

‘We’re not discovering a whole lot of new lions, tigers, and bears, but there’s an incredible potential for discovery of new species of small mammals,’ he said.

Specimens of the stilt mice studied by the team - the already-known species C. goslingi on the left, and the new species C. lumumbai on the right

Specimens of the stilt mice studied by the team – the already-known species C. goslingi on the left, and the new species C. lumumbai on the right

‘They’re sort of under-appreciated animals – they’re really cool when you start to learn about their ecology. These are semi-aquatic mice, so they’re not just your average, everyday rodents.’  

Dr Terry Demos, also at the Field Museum, added: ‘To cross one of the rivers where I caught a Colomys, you have to use walking sticks, the water’s up to your waist.

‘And you can have torrential rain in the tropics, so sometimes half the traps get swept away, and you have to go downriver to try to find them.’

For this study, the researchers analysed the stilt mice’s physical traits and DNA and discovered two entirely new species within the Colomys genus.

The team named the species Colomys lumumbai and Colomys Wologizi, after the Congolese independence leader Patrice Lumumba and Liberia’s Wologizi Mountains.

Rangers from Itwombe Natural Reserve crossing a river to get to the shallows on the other side to collect stilt mice

Rangers from Itwombe Natural Reserve crossing a river to get to the shallows on the other side to collect stilt mice

Learning about the different species of mice in streams halfway around the world has broad implications for conservation science, according to the team.

Dr Demos said: ‘The new species we named are part of a global effort to understand the biodiversity of African rainforests and highlight the critical areas to be preserved.

‘There are vast areas of the Congo Basin that have barely been explored in the last seventy years, places that are hard to access due to political instability.

‘We’re not even completely sure how these animals are distributed, there are big gaps,’ adding that the findings could help inform public health efforts.

Dr Giarla added: ‘COVID is a zoonotic disease, and biodiversity research is essential to understanding zoonotic disease. We need to understand what species are present in natural areas, especially natural areas being changed by humans.’

The research has been published in the Zoological Journal of the Linnean Society. 


Nature is in more trouble now than at any time in human history with extinction looming over one million species of plants and animals, experts say.

That’s the key finding of the United Nations‘ (UN) first comprehensive report on biodiversity – the variety of plant and animal life in the world or in a particular habitat.

The report – published on May 6, 2019 – says species are being lost at a rate tens or hundreds of times faster than in the past. 

Many of the worst effects can be prevented by changing the way we grow food, produce energy, deal with climate change and dispose of waste, the report said.

The report’s 39-page summary highlighted five ways people are reducing biodiversity:

– Turning forests, grasslands and other areas into farms, cities and other developments. The habitat loss leaves plants and animals homeless. About three-quarters of Earth’s land, two-thirds of its oceans and 85% of crucial wetlands have been severely altered or lost, making it harder for species to survive, the report said.

– Overfishing the world’s oceans. A third of the world’s fish stocks are overfished.

– Permitting climate change from the burning of fossil fuels to make it too hot, wet or dry for some species to survive. Almost half of the world’s land mammals – not including bats – and nearly a quarter of the birds have already had their habitats hit hard by global warming.

– Polluting land and water. Every year, 300 to 400 million tons of heavy metals, solvents and toxic sludge are dumped into the world’s waters.

– Allowing invasive species to crowd out native plants and animals. The number of invasive alien species per country has risen 70 per cent since 1970, with one species of bacteria threatening nearly 400 amphibian species.

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