Interpretation of behavioural reactions of sheep towards fear-eliciting situations
Publication Type: |
Journal Article |
Year of Publication: |
1998 |
Authors: |
M. Vandenheede, M. F. Bouissou, M. Picard |
Publication/Journal: |
Applied Animal Behaviour Science |
Keywords: |
fear reactions, livestock, principal component analysis, sheep |
Abstract:
The relationships between 27 behavioural variables, displayed by 206 sheep in three tests used to measure fear in sheep, were assessed using Principal Component Analysis. These animals were individually subjected to the same standardised fear-eliciting situations: isolation from conspecifics (I), a surprise effect (S) and the presence of a human (H). The first component (which explained 30.1% (I), 29.4% (S) and 34.8% (H) of the total variance) was interpreted as anxiety or fear induced by social isolation which is common to the three tests. Effectively, eight variables related to feeding, locomotor activity and localisation in the test pen showed consistent and high loadings on component 1 for the three tests. In order to simplify the methodology, a `fear mark’ was computed using the three major items related to component 1 for the three tests: the time spent feeding, the time in square 5 (location of the trough) and in squares 1, 2 and 3 (away from the stimulus and the trough). This method of scoring allows positioning of an animal on a continuous scale and therefore direct comparisons with other groups of animals, using a simplified methodology. Other behavioural variables showed high loadings on component 2 in S and in H: this component was interpreted in terms of `close interaction’ with the stimulus in S and in terms of `panic’ in H. An `interaction mark’ (S) and a `panic mark’ (H) were computed using the major behavioural items. These marks could improve the interpretation of behavioural reactions of sheep towards a surprise effect and the presence of an immobile human.