African wading rats

Rat that uses whiskers to hunt underwater prey is really four species

African wading rats have very sensitive whiskers

Velizar Simeonovski, Field Museum

An elusive type of wading rat armed with super-powered whiskers is actually four separate species, researchers have found.

African wading rats, formerly the single species Colomys goslingi, are truly unusual rodents. They are one of the only semi-aquatic rodents in Africa, striding into streams on long, stilt-like feet. There, they drape long whiskers on the water’s surface, sensing the vibrations of their prey: aquatic insects, tadpoles and small fish moving underwater.

“It was known all the way from Liberia to Kenya, which is an insanely wide distribution for a really small animal,” says Tom Giarla at Siena College in Loudonville, New York.

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This cross-continental range stood out to Giarla and his colleagues, who wondered if the territory was actually inhabited by a series of hidden species.

The team examined dozens of wading rats in museum collections and captured specimens across their wild range. They carefully compared the rodents’ physical feature, and analysed samples of their DNA. The team also compared the rats with the similar Ethiopian amphibious rat (Nilopegamys plumbeus), which was only collected once in 1927 and may be extinct.

Two of the wading rat populations in the Congo basin and West Africa were distinct, unrecognised species. The team named them Colomys lumumbai and Colomys wologizi, respectively. The team also discovered that a Colomys goslingi subspecies in Cameroon was a full species, and that the wading rat’s closest genetic relative is the mysterious Nilopegamys.

Giarla says he is most interested in learning more about how the new species interact with their environments. Understanding the rats’ habitat requirements is crucial because their rainforests are threatened by deforestation, mining and political strife.

“Species cannot be adequately conserved and protected unless they are described,” says Emily Roycroft at the Australian National University in Canberra. “I’m hopeful that this study and future studies will aid the conservation of African biodiversity into the future.”

Journal reference: Zoological Journal of the Linnean Society, DOI: 10.1093/zoolinnean/zlaa108

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