Tail biting in pigs is a problem of modern pig production and can occur at all stages in the production cycle. It leads to tail damage of varying severity (see Hunter et al., 1999) and can include swelling and infection, which travels up the spinal cord causing abscesses in the lungs, and pyaemia (a type of septicaemia causing widespread abscesses in the organs (see Schröder-Pedersen and Simonsen, 2001 for full details). Tail biting is therefore a serious welfare issue. In order to reduce the risk of tail biting in modern pig production systems, producers dock the tails of pigs, either with side cutting pliers or gas-heated cautery clippers. Tail docking does not eliminate tail biting however, and is a procedure that causes acute and transient pain, with potential long term chronic discomfort.