Continual monitoring, using chocolate wax blocks is central to the success of this project. Vital to this is an ability to recognise teeth marks on the blocks and to ascertain whether any of these belong to rats.

The block in the photograph below has been nibbled by mice:

Shrews have even smaller, finer nibble marks:

Rats toothmarks are larger than mice:

Rats have two noticeable grooves, whereas rabbits (below) have four grooves on top, with a large single one below: 

Birds also peck the wax blocks and leave a set of pointed grooves as shown below:

These bird grooves are often quite deep.

Mouse photo Bob Swann, other photos Biz Bell, WMIL

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