Someone on the Wild About Britain forums told me this: that if you grab a wood mouse's tail, the skin sloughs off painfully, and then that portion of the tail dies and falls away. I found this dead wood mouse in a field and tried to move it so I could take a picture, and sure enough, away came the tail skin. It's a survival strategy, but a costly one. The correct way to hold a wood mouse is by its scruff, like the yellow-necked mouse and bank vole here: http://urbanextension.wordpress.com/2008/10/11/a-morning-with-mice-voles-shrews-moths-at-corfe-mullen-meadow-reserve/
Short walk this afternoon down Edgeley Road revealed this water vole latrine. It seems very late in the year to be seeing latrines. Does that mean late-breeding females?