Individual differences in behavioural responses of pigs exposed to non-social and social challenges

Abstract

The existence of individual differences in behaviour is a rarely considered but almost universal phenomenon. Individual differences in behaviour may reflect the existence of stable temperamental characteristics which could be used to improve understanding of behavioural mechanisms and to predict individuals' responses at different ages and in different contexts. In farm animals, the study of temperament has been largely restricted to dairy animals and to a limited range of contexts. This study examined the consistency of individual differences in responsiveness to a number of non-social and social challenges in female pigs. Two separate groups of gilts were exposed to a series of handling tests including willingness to leave the group residential pen, ease of movement through a corridor, response to a sudden human approach, resistance to restraint and vocalisation response to restraint. With the exception of vocalisation during restraint, individual scores for these tests tended to correlate and the scores for the correlated tests were therefore summed and 8 low scoring and 8 high scoring gilts selected from each group. The responses of these low and high responders to a novel object and to a group feeding test were then measured. In the novel object test, high responding gilts expressed overall a greater attention to the novel object. In the group feeding test there was no difference between low and high responders in the number of attacks won or lost but high responders won a significantly greater proportion of encounters. It was possible therefore to identify in female pigs, individuals that responded consistently to a variety of non-social challenges. In a social challenge test, however, not all elements of response were consistent with previously measured responses to non-social challenge. The variation between responses to social and non-social challenge in the present study suggests more than one underlying behavioural dimension controlling responses to challenge in female pigs.