This month, NHSN naturalist, Chris Wren takes a focus on the Greater White Toothed Shrew in the North East.
It is not every day that a new terrestrial mammal species is recorded in the UK. In fact the Greater White-toothed Shrew (Crocidura russula) is the first in a century, discovered only four years ago. It came to notice when a photo of a shrew brought in by a cat in Sunderland was posted on Facebook and was noticed by local mammalogist and ecologist Ian Bond. It looked different from any of our native shrews and was subsequently confirmed to be a new British species. How it got here is not established but looking back at earlier photos of dead shrews it has probably been present at least since 2015.
You can’t see the white teeth unless you have a live-trapped or dead animal but the Greater White-toothed Shrew can be identified by being medium-sized for a shrew, having grey fur, large protruding ears, white hairs on its tail and a distinctive nose profile described as looking like a Womble or a Clanger (if you are young enough to remember those). The zoomed-in screen grabs from trail camera video freeze-frames aren’t the best quality but this is the nose shape and large ears,
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and here you can make out the white tail hairs.
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All these are clearer on the trail camera video. These few clips are all I have so far and because we are looking at a shrew they are fairly brief.
The camera box was placed close to a hedgerow in Elemore Park, only a mile or so from Easington Lane where the original Greater White-toothed Shrew was recorded. A few interesting observations about the recordings: all were in daylight and Greater White-toothed Shrews are known to be mainly diurnal in habit; there were a few Common Shrew recordings but no Pygmy Shrews, a few Field Voles but no Bank Voles; and no Wood Mice, which was a surprise. I had enough videos of Common and Greater White-toothed Shrews to make this short slow-motion comparison video.
The Greater White-toothed Shrew is a resident of much of Western Europe and some of the Channel Islands. It was discovered in Ireland in 2007 and is causing concern there because its spread has completely displaced the native Pygmy Shrew. The small mammal ecology of Ireland is different from ours as there is only one native shrew, one mouse (Wood Mouse) and one vole (Bank Vole, accidentally introduced in the 1920s). The Greater White-toothed Shrew lives at much higher densities than the Pygmy Shrew and probably out-competes it by eating all the food. Since its discovery here a monitoring programme has been put in place by the Mammal Society, mainly involving barn owl pellet dissection, to monitor the spread of the Greater White-toothed Shrew and its effect, if any, on the Pygmy Shrew. It won’t necessarily have the same impact as in Ireland as the small mammal ecology of Great Britain is different with a wider range of small mammals and predators. In Ireland this is classed as an invasive species but although there is now evidence that the Greater White-toothed Shrew has spread across the eastern half of County Durham the effect on Pygmy Shrews is unknown, so here it is a non-native species. Genetic analysis suggests the Sunderland shrew came from France and not from Ireland.
Our three native shrew species, Common Shrew (Sorex araneus), Pygmy Shrew (Sorex minutus) and Water Shrew (Neomys fodiens), all have red-tipped teeth whose enamel is strengthened with iron. As a reminder, here is what they look like on trail camera. The Pygmy Shrew is very small and slim with a long furry tail. The Common Shrew is chunky in build, has only a medium length tail and is tricoloured on the sides, dark, medium and light. The Water Shrew is large and is black and white.
The discovery of the Greater White-toothed Shrew highlights the importance of citizen science and recording observations. Mammals are some of the most under-recorded species in Britain so if you see a shrew or any small mammal be sure to report it to the Mammal Society or to iRecord.