The European water vole or northern water vole, Arvicola amphibius (formerly A. terrestris), is a semi-aquatic rodent. It is often informally called the water rat, although it only superficially resembles a true rat. Water voles have rounder noses than rats, deep brown fur, chubby faces and short fuzzy ears; unlike rats their tails, paws and ears are covered with hair.
In the wild, on average, water voles only live about five months. Maximum longevity in captivity is 2 and a half years
Water voles reach 140–220 millimetres (5.5–8.7 in) in length plus a tail of 55–70 millimetres (2.2–2.8 in) of this. Adults weigh from 160–350 grams (5.6–12.3 oz), juveniles weigh less but must reach around 140–170 grams (4.9–6.0 oz) to be able to survive their first winter.