The behavioural patterns of domesticated pigs are well conserved from their ancestors. This suggests that the underlying motivational systems are similar to those of wild boar and feral domestic populations. This chapter describes how commercial conditions, whilst providing some welfare benefits, can constrain behavioural expression. The chapter reviews the behavioural ecology of pigs, introduces the concept of behavioural needs and considers the developmental and additive genetic basis behind individual differences in behaviour. It looks ahead to future trends in research in this area and provides suggestions for extensive further reading on the subject.