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UBC Theses and Dissertations

Facial expression, vocalizations and eye temperature as potential indicators of pain in harbour seals (Phoca vitulina) MacRae, Amelia Mari


Pain assessment in animals typically relies on a combination of physiological and behavioural measures. Unfortunately, many of these measures require handling the animals or physical sampling, which are invasive and can result in a stress response. The aim of this thesis was to identify some possible non-invasive indicators of pain in harbour seals as no clear species-specific indicators had been established. I investigated whether or not seals showed changes in facial expression and other behaviours (Chapter 2), vocalizations (Chapter 3), or eye temperature (Chapter 4) in response to the routine procedures of flipper-tagging and microchipping. Seals showed changes in facial expression and in several other behaviours in response to the procedures. Most notably, orbital tightening increased from before to after tagging and microchipping (p < 0.001), whereas the behaviours of looking around (p < 0.01) and struggling (p < 0.05) decreased. Sham treatment produced no similar changes (Chapter 2). The number of vocalizations increased from before tagging to after (p < 0.001) and the peak frequency increased from 837.1 ± 75 Hz before to 1041 ± 75 Hz after (mean ± SEM; p < 0.01). Similarly, there were more vocalizations after chipping than before (p < 0.001), and peak frequencies of the calls increased from 848.8 ± 79 Hz before to 1111.2 ± 79 Hz after (mean ± SEM; p < 0.05). No similar changes in vocalizations were seen after sham treatments (Chapter 3). Lastly, seals’ eye temperature increased after tagging but not after sham-tagging (p < 0.05), suggesting that a rise in eye temperature may reflect pain. However, eye temperature also increased in response to handling and an injection of lidocaine, suggesting change in eye temperature is non-specific to pain. Lidocaine, at the dosage used, did not appear to have a mitigating effect on the pain from tagging and chipping (Chapter 4). These results show promise for the use of facial expressions and other behaviours, including vocalizations, to assess potentially painful procedures in seals. Similarly, the use of eye temperature has potential to indicate a stress response and to evaluate the potential aversiveness of routine procedures in this species.

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