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Cognitive sciences to relate ear postures to emotions in sheep
- A Boissy, A Aubert, L Désiré, L Greiveldinger, E Delval, I Veissier
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- Journal:
- Animal Welfare / Volume 20 / Issue 1 / February 2011
- Published online by Cambridge University Press:
- 01 January 2023, pp. 47-56
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Emotions are now largely recognised as a core element in animal welfare issues. However, convenient indicators to reliably infer emotions are still needed. As such, the availability of behavioural postures analogous to facial expressions in humans would be extremely valuable for animal studies of emotions. The purpose of this paper is to find out stable expressive postures in sheep and to relate these expressive postures with specific emotional contexts. In an initial experiment, we identified discrete ear postures from a comprehensive approach which integrates all theoretically distinguishable ear postures. Four main ear postures were identified: horizontal ears (P posture); ears risen up (R posture); ears pointed backward (B posture); and asymmetric posture (A posture). In a second experiment, we studied how these ear postures were affected by specific emotional states elicited by exposing sheep to experimental situations in which elementary characteristics (ie suddenness and unfamiliarity, negative contrast and controllability) were manipulated. We found that: i) the horizontal P posture corresponds to a neutral state; ii) sheep point their ears backward (B posture) when they face unfamiliar and unpleasant uncontrollable situations, hence likely to elicit fear; iii) they point their ears up (R posture) when facing similar negative situations but controllable, hence likely to elicit anger; and iv) they expressed the asymmetric A posture in very sudden situations, likely to elicit surprise. By cross-fostering psychological and ethological approaches, we are able to propose an interpretation of ear postures in sheep relative to their emotions.
Spatial distance and reactivity traits alter the positive perception of brushing by ewes
- P. R. Tamioso, A. Boissy, X. Boivin, H. Chandèze, S. Andanson, É. Delval, C. A. Taconeli, D. Hazard, C. F. M. Molento
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Gentle handling seems to elicit positive states in sheep. The study investigated whether spatial distance alters sheep responses to brushing and whether spatial distance is influenced by reactivity. Twenty Romane ewes were assessed in three sessions: in Sessions 1 and 3, one grid separated the test animal from pen mates, with no distance between them, and in Session 2 two grids separated the test animal from pen mates by a distance of about 1.7 m. Ewes had been genetically selected for low (R−) or high (R+) behavioural reactivity to social isolation. Body postures, head orientation, ear postures, closed and half-closed eyes, tail wagging and feeding behaviour, in addition to heart rate (HR) and HR variability, as the root mean square of successive differences (RMSSD), standard deviation of all normal-to-normal (NN) intervals (SDNN), RMSSD/SDNN ratio and ratio between low-frequency (LF) and high-frequency (HF) powers (LF/HF) were assessed. Data were analysed using generalized linear models and linear mixed models. Session, genetic line and phase (pre-, brushing and post-brushing) were considered fixed effects. Increased distance in Session 2 might not have influenced ewes’ responses. Fewer changes in ear postures were noted in Session 3 than 1 (P<0.01), suggesting that ewes were more relaxed in Session 3. The RMSSD/SDNN ratio was higher mainly during brushing in Sessions 1 and 3 (P<0.05), indicating that ewes were more relaxed during brushing, and at no distance between pen mates. However, spatial distance influenced R− and R+ ewes’ responses; R+ ewes performed more asymmetric ear postures in Session 2 than 1 and 3 (P<0.01), and in Session 3 than 1 (P<0.01), indicating that spatial distance had a negative effect on R+ ewes. Low reactive ewes spent less time on horizontal ear postures in Session 2 than 1 and 3 (P<0.01), and R+ ewes spent more time on horizontal postures in Session 1 than 3 (P<0.01). Curiously, R− ewes spent more time eating and ruminating in Session 3 than 1 (P<0.01), and in Session 2 than 1 and 3 (P<0.01), whereas R+ ewes ate and ruminated more in Session 1 than 3 (P<0.05). Higher HR was found among R− ewes in Session 2 than 1 and 3, and in Session 3 than 1 (P<0.01). High reactive ewes showed higher HR in Session 1 than 3 (P<0.01). The findings suggest that the social context might influence sheep responses to gentle handling, and the effects depend on their reactivity traits.