Why you'll never find water voles living in a stony-bottomed stream

I've been watching a water vole swimming below the surface for the last half hour, and noting how, when the vole feels threatened, it kicks up a cloud of mud to hide itself (see second picture down) before slipping into an underwater burrow. A mud or silt screen is a really important defence mechanism, so it's crucial for good habitat.

I include a photo of a new burrow that's appeared over the last week - note the neatness of the entrance and the grazing around it.