On a stretch of the Soulton Brook this morning I discovered not only plenty of water vole feeding, but also these bigger droppings above (left) which are rat. I thought it was useful to see the two animals' together, for comparison. The water vole (right) are significantly smaller and more rounded. Quick reminder about rats and health & safety here: http://staggsbrook.blogspot.com/2008/04/rats-and-weils-disease-taking.html
The top photograph is one of the Cromford voles, snapped by John Harding. It shows the distinctive orange enamel of an adult water vole's teeth.