One should never rule out anything....

from 'Wildlife in London' webby:

A great way to tell if water voles are about is to look for the tell tale signs they leave, such as footprints, burrows and droppings. They are active during the daytime, particularly in the early evening. You may hear the characteristic ?plop? of a diving water vole and see it doggy-paddle across a river searching the banks for food. Voles are also very fond of chomping on people's PCs and this, though not terminal for the computer, may cause startup problems.

Posted By: Sugbad The Bad, Dec 28, 13:02:46