The Mysterious African Wading Rat

Photo One fromhttps://www.newscientist.com/article/2256702-rat-that-uses-whiskers-to-hunt-underwater-prey-is-really-four-species/ by Velizar Simeonovski, Field Museum
The African Wading Rat (Formerly known as Colomys goslingi) (Photo One)

Dear Readers, many of you were so convinced that it was April 1st when I reported on tardigrades last week that I thought I’d give another unlikely creature its moment in the spotlight today. The African Wading Rat was formerly thought to be just one species (Colomys goslingi), but recent studies have found that there are at least four different species, found from Liberia to Kenya.

However, the interesting thing about the African Wading rat is that it hunts for its food (insects, small fish and the occasional tadpole) in streams and rivers. This is most unusual behaviour for a rodent. Furthermore, it uses its long whiskers to sense the presence of prey by draping them on the surface of the water. And, finally, it apparently strides into the water with its ‘stilt-like feet’. What’s not to love?

Photo https://www.semanticscholar.org/paper/The-African-rodent-Colomys-goslingi-Thomas-and-%2C-(-Parey/de568cae8f2f0089e3c37d801b87275cdebda889 from
Photos from the 1907 Wading Rat study (Photo Two)

Until recently, the main study of these rodents seems to have been in 1907, hence the quality of the photos above. The wading rat was seen using its whiskers to hunt for tadpoles (sorry to any of my frog-loving readers). Unfortunately the rodents were then killed and their stomach contents examined to see that they ate, well, tadpoles. Thank goodness for the more observational approach taken by most scientists today.

We have no idea how many wading rats there are, where they live or what they get up to, but the scientists who discovered how varied they are are obviously concerned about all the usual things – deforestation, political strife and mining. And their closest relative is none other than the Ethiopian amphibious rat (Nilopegamys plumbeus), known to science from a single animal found in the 1920s. The animal lived close to the source of the river Little Abbai in North-Western Ethiopia, but the area has long been degraded by over-grazing, and is now apparently completely destroyed. From the one specimen that we have, it’s clear that the rat was extremely well adapted for the aquatic life, with enlarged back feet to help with swimming and a dense coat to keep it warm in the water.

Photo Three fromhttps://www.globalwildlife.org/lost-small-mammals/
Ethiopian aquatic rat (Nilopegamys plumbeus) (Photo Three)

Furthermore, both the Ethiopian and the African species described above seem to have large brains compared to other rodents of a similar size. In creatures like raccoons, the areas of their brains associated with their sensitive hands are much enlarged, so maybe the ‘whisker area’ of these animals’ brains is particularly well-developed: they have a lot of complex processing to do when they’re trying to find and catch their aquatic prey.

There have been two attempts to find the Ethiopian aquatic rat, but no luck so far. It’s probably worth asking the local people (if that hasn’t happened already) as they are usually the ones who know what animals can be found where. At any rate, let’s hope that the wading rats that are going about their business all over Africa don’t end up disappeared in the same way as their Ethiopian cousin. We need all the biodiversity that we can get.

Photo Credits

Photo One from https://www.newscientist.com/article/2256702-rat-that-uses-whiskers-to-hunt-underwater-prey-is-really-four-species/ by Velizar Simeonovski, Field Museum

Photo Two from https://www.semanticscholar.org/paper/The-African-rodent-Colomys-goslingi-Thomas-and-%2C-(-Parey/de568cae8f2f0089e3c37d801b87275cdebda889

Photo Three from https://www.globalwildlife.org/lost-small-mammals/

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