Bonobo emotions unveiled : insights into cognitive, behavioural, and welfare components
Emotions are an integral component of the daily lives of animals as they enable flexible responses to rewarding and aversive stimuli, thereby guiding behaviour. They are also major determinants of an animal’s welfare. Emotions are notoriously difficult to measure reliably, partly due to their species- and individual-specific nature. In this thesis, I explore animal emotions by focusing on the cognitive and behavioural components in zoo-housed bonobos (Pan paniscus). Using a combination of touchscreen and eye-tracking technology, I investigated attentional biases towards different stimuli. While completing a pictorial emotional Stroop task, I found that attention of the bonobos was attracted by non-social images such as leopards, food items, and flowers, alongside positive facial expressions, offering potential insights into the socio-ecological priorities of bonobos. Attention can, however, also be modulated by an animal’s own emotional state. To study such affect-congruent attention biases, I designed an eye-tracking study in which I primed emotions and subsequently studied preferential looking at competing facial expressions. Priming emotions using salient videos generally induced pupil dilation, although attention of the bonobos was captured by negative facial expressions, irrespective of the video type. Shifting focus to behavioural outputs of emotions, I examined two indicators typically used to measure negative emotions: abnormal behaviours and self-directed behaviours. Factors such as sex, rearing history, and personality traits explained inter-individual variation in the performance of abnormal behaviours and revealed potential welfare implications. I furthermore identified two self-directed behaviours that were associated with negative emotional arousal. Not only the type of behaviour, but also how a behaviour is performed can inform us about emotions. As such, I developed a Qualitative Behavioural Assessment to study how humans perceive bonobo emotional expressivity. While expert knowledge proves crucial for rating expressive qualities, further validation and inclusion of caretaker knowledge are essential for continued tool development. In the final study, I integrated cognitive and behavioural components of emotions within an animal welfare context. Managed fusion events between bonobo subgroups were characterised by increases in aggressive and socio-sexual interactions. Touchscreen testing also indicated cognitive signs of shifts towards negative emotions in the bonobos, although short-lasting. Correlates between cognitive and behavioural measures revealed additional emotional consequences of behaviours. In conclusion, this thesis offers a multifaceted exploration of animal emotions, emphasising the importance of species-specific measures and individual factors in understanding and assessing animal welfare.
Antwerp : University of Antwerp , 2023
269 p.
Supervisor: Eens, Marcel [Supervisor]
Supervisor: Stevens, Jeroen [Supervisor]
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Creation 30.11.2023
Last edited 18.01.2024
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