Assessment of personality types in Nigerian dwarf goats (Capra hircus) and cross-context correlations to behavioural and physiological responses

Abstract

The assessment of personality in farm animals and its relation to other behavioural and physiological traits is of growing scientific and practical interest. Therefore, the aims of the present study were first to assess the personality of dwarf goats in the context of the proactive/reactive dichotomy and second to elucidate cross-context correlations to other individual patterns in behaviour and physiology. We measured the behaviour of 108 Nigerian dwarf goats in repeated (two test periods within two weeks) open-field and novel-object tests to classify the subjects into proactive, reactive and intermediate personality types. In addition, we investigated the possible inter-relationships of inter-individual differences in personality with behaviours in other test situations and physiological measures (heart rate variability). To identify individual personality types, we selected the 11 most appropriate behavioural measures, identical in both test periods, from a total of 82 observed behaviours. Using these behaviours, we ran two separate principal component analyses (PCA1 and PCA2) for the two test periods. We found two main principal components (PCs), which were interpreted as “boldness” (PC1) and “activity” (PC2) and were identical in both PCAs. Based on PCA1, 30 goats could be grouped as the proactive, 25 as the reactive and 53 as the intermediate personality type. In PCA 2, 66 individuals (61%) showed a consistent personality type compared to PCA1. Goats that scored highly on PC2 were also more active in a social separation test, while no correlations were found between PC1 or PC2 and the dominance status. Regarding heart rate variability, the standard deviation of R-R intervals (SDNN) was positively correlated with PC2, while a negative correlation was found between PC1 and SDNN. PC2 was also positively correlated with weight gain. The present study is the first to quantify temporarily consistent and cross-context correlations of individual behavioural and physiological differences in goats. The relatively small number of animals that showed the same extreme behavioural phenotype in both test periods is in good agreement with studies on personality types in cattle and pigs and shows that intermediate and flexible personality types make up the main part of a population. The results provide new opportunities to investigate the inter-relationships of inter-individual differences in personality traits with other physiological measures and cognitive abilities in goats.