I had a mouse in the kitchen and put a trap down before I went to work.
The trap caught the mouse but by its back half. Obviously the mouse had still been alive and tried to get away by going under the skirting board. The front half of the mouse got under the board but the back half, with trap attached couldn't make it.
By the time I got home from work the mouse was dead and rigor mortice had set in so when I tried to get the mouse out it snapped in half, leaving the front half stuck under the skirting board.