ABSTRACT
Animal behaviour is central to one of the most popular definitions of welfare that requires that animals should have the opportunity to behave naturally (Kiley-Worthington 1989; Rollin 1993). The opportunity to express natural behaviour is therefore viewed by some as a cornerstone of what it means to be in a good state of welfare. Consequently, the execution of species-typical behaviour is therefore seen as an important welfare assessment tool. According to another definition, good animal welfare is when animals are ‘healthy and have what they want’ (Dawkins 2008). Highly motivated behaviours may be thwarted when housing or management practices prevent pigs from ‘having what they want’. The consequence of thwarting highly motivated behaviours has implications in its own right for the welfare of the individual and its group mates. Behaviour, as well as being an indicator of welfare state, therefore also plays a central role itself in some of the most intractable welfare problems in modern production. Indeed, many welfare problems (e.g. tail biting, belly nosing, fighting, maternal crushing and savaging of neonates, vulva biting, heat stress; Fig. 1 and 2) cannot be understood without knowledge of behaviour of domestic pigs and their wild ancestors. This chapter seeks to provide the basis with which to understand the aetiology of some of the prevalent welfare conditions by referring to the behavioural ecology of pigs and the mismatch between highly motivated systems and the opportunities for their behavioural expression under commercial production. It also considers the evidence for, and causes of, individual variability in the expression of behavioural traits that affect welfare.
