I've posted before about the characteristic star-shaped footprints water voles often leave in soft mud. The second photo down shows the splayed toe formation of the hind foot very clearly (as modelled by "Spot").
This blog charts the fortunes of water voles in and around the Whitchurch area, North Shropshire. Water voles are one of the UK's most threatened mammals, extinct in many counties, and so it's vital they receive as much monitoring and protection as there is going. Here in Whitchurch we're lucky enough to have them right in the middle of town - how cool is that?