Recognising emotional expressions in captive bottlenose dolphins: Can lay observers agree using qualitative behavioural assessment?

Abstract

This study applies qualitative behavioural assessment (QBA) to bottlenose dolphins Tursiops truncatus. Ten observers recruited through convenience sampling, who were unfamiliar with bottlenose dolphins and managed care of cetaceans, were instructed to use a Free Choice Profiling methodology to assess 20 video clips showing captive dolphins in a range of environmental and contextual settings. QBA scores were analysed using Generalised Procrustes Analysis, which shows a high level of agreement between observers (74.21% P<0.001) and generated three main consensus dimensions together explaining 61.9% of the variation between observer scoring patterns. Dimension 1 was characterised as ranging from ‘energetic/active/excited’ to ‘calm/bored/sad’, Dimension 2 as ranging from ‘happy/playful/calm’ to ‘frustrated/aggressive/annoyed’, and Dimension 3 from ‘focused/engaged/curious’ to ‘unwilling/shy/nervous’. Dolphin behaviours observed in the QBA clips were scored by the experimenter using an ethogram of 37 behavioural categories, and then correlated with the three consensus dimensions using Spearman’s rank correlation. Dimension 1 correlated with ‘porpoising’ (r_s=0.484), ‘wait horizontally’ (r_s=0.481) and ‘face object’(r_s=-0.469), all at P<0.05; Dimension 2 with ‘spy hop’ (r_s=0.480), ‘head following’ (r_s=0.463), ‘bubble single’ (r_s=0.463), ‘jaw clap’ (r_s=-0.521) and ‘bubble stream’ (r_s=-0.518), all at P<0.05; and Dimension 3 with ‘ball toss’ (r_s=0.621), ’dynamic swim’ (r_s=-0.632) and ‘avoid trainer’ (r_s=-0.624) at P<0.01, and ‘carry object with mouth’ (r_s=0.523) and ‘touch trainer’ (r_s=-0.558) at P<0.05. These findings indicate that QBA appears to be a suitable tool for assessing emotional expressivity in captive dolphins. Potentially meaningful associations between QBA dimensions of dolphin expressivity and ethogram-based behaviours are discussed but need further substantiation in future research.