Water Vole – Arvicola amphibius
Rat-sized with dark chestnut-brown/black fur. Blunt muzzle and short rounded ears. Hair-covered tail about half the length of head and body. Makes a characteristic ‘plop’ when entering the water. Swims with much of the body showing above the surface but may also swim totally under the water.
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Droppings: Water vole droppings are particularly distinctive as they are often described as having a tic-tac shape—no other mammal has droppings comparable to the water vole. Droppings are usually found in latrines and in small heaps close to water. Width 8-12mm, 4-5mm thick. Variable in colour – usually dark green when broken up. Odourless.
Feeding signs: Nibbled stalks of grass in small piles along tunnels in long grass indicate the presence of water voles. However, field voles and bank vole do leave similar feeding signs, so always look for supporting evidence, ideally droppings. Water voles can be seen during the day feeding on grasses and reeds, sitting on their hind feet and holding a stalk in front of their paws. They will bite the grass at 45 degree angles, as shown in the photo.
Brown rat (Rattus norvegicus)
Grey/brown coat on top with grey underside, compared to chestnut brown colour of water vole. More pointed muzzle than water vole, which has more of a blunt muzzle. Hairless tail, 90% length of body, proportionately longer than water vole’s, which is 60%. Rat ears are bigger and much more prominent than water voles, which are very subtle, usually covered by fur.
Field vole (Microtus agrestis)
Much smaller than water vole, with head and body length of 9-12cm, compared with 14-22cm for water vole. Yellowish or grey/brown, much lighter than water vole which has darker chestnut brown fur. Tail shorter than water vole tail, only 30% length of head & body, whilst water vole’s is 60%.
Bank vole (Myodes glareolus)
Bank vole much smaller than water vole with head and body length of 9-11cm compared to 14-22cm. Water vole tail is slightly longer than that of bank vole, with it being 60% head and body length compared to 50%.
Derek Crawley, Staffordshire Mammal Group, says:
“Water voles can be quick and very hard to see on the bank of a water course, but once they start swimming then the movement catches the eye. Here, the fact that their whole body is above the water, whereas a rat shows just the head, makes recognition easier.”