Behavioural consistency during social separation and personality in dairy cows

The concept of personality implies intra-individual consistency of behavioural and physiological responses towards given situations over time. In this study, we investigated the long-term intra-individual consistency of the reaction towards social separation in dairy cows, Bos taurus taurus. In 35 animals, behavioural and adrenocortical reactions towards a 20 min social separation were examined. The separation test was carried out four times over a period of two lactations. Our subjects showed the expected reactions of cattle towards social separation such as exploration, walking, vocalisation, defecation, urination, and an increase in saliva cortisol concentration. We calculated a high repeatability of all behaviours tested and of saliva cortisol response towards this stressor throughout two lactations. Particular parameters (saliva cortisol response, duration of exploration, and number of entered squares) decreased across repetitions indicating a habituation. In contrast, the frequency of vocalisation, vigilance, and walking did not change across repetitions. Consequently, the different temporal changes of the measures may reflect that the response is mediated by different motivations. To address this issue, we examined the potential underlying structure of behaviour using principal component analysis. We could distinguish three principal components reflecting sociability, exploration, and anxiety. These three components are included in two (Neuroticism, Extraversion) of the five main dimensions known from human personality structure. In conclusion, the intra-individual behavioural consistency can be explained in terms of underlying personality structures, which show considerable generality across species. In farm animals, consideration of personality structures may be crucial concerning animal welfare.