Average male body length is 210 mm, with females averaging 187 mm. Tail length averages 124 mm in males and 116.5 in females. Males average 263 g, while females average 232 g (Thompson, 1964).
With a dense coat of fur, small, rounded ears, and short tail, A. amphibius resembles other voles of similar size. Water voles are relatively large voles. Their pelage is thick and extends from the head to the end of the tail. Coloration ranges from light to dark brown on top (sometimes black); and from white to slate gray on their underside. This coloration makes them difficult to see in the dense vegetation they prefer. Claws on each of the feet are well developed, and flank glands on the sides of the body used to mark territory are visible most of the time as well. Water voles possess the typical rodent dental formula and posses continuously growing cheek teeth (Niethammer, 1990; Nowak, 1991).
Range mass: 70 to 250 g.
Range length: 120 to 220 mm.
Other Physical Features: endothermic ; bilateral symmetry