Facial Expressions and Behaviours Associated with Pain in Japanese Macaques

概要

Nonhuman primates (NHP) are extensively used in biomedical research due to their close
evolutionary relationship with humans. Invasive research might cause pain, affecting the animals'
quality of life and biasing study outcomes. Pain is a complex, unique experience with sensory,
emotional and cognitive components; thus significant interindividual variability in pain expression
is expected. Pain assessment in NHP is challenging because macaques tend to mask pain when an
observer is present. Moreover, few signs of pain have been documented in NHP species, making
it harder to know where observers should focus their attention when evaluating animals. Several
methods can be used to assess pain in macaques, including physiological variables, behaviour,
vocalisation and facial expressions. Automated systems have recently been implemented for pain
recognition in animals due to their potential to help reduce animal suffering while reducing the
time of human annotation bias and fatigue-related errors.
The main aim of this thesis was to identify pain indicators in captive Japanese macaques. The
female macaques observed in this study underwent laparotomy for other research purposes, and
data were collected opportunistically. Analgesics were administered during surgery and for three
days after surgery. The hypotheses were that 1) animals decrease their overall activity after surgery
due to pain or discomfort, 2) animals would show facial signs associated with pain, mainly one
day after surgery, but not one week later, and 3) automated identification of faces from videos
recordings followed by pain classification using deep learning would have accuracy above chance.
Chapter 2. Assessment of postoperative behaviour in captive Japanese macaques
Chapter two explores the differences between preoperative and postoperative behaviour in captive
macaques. For that, an ethogram was developed to code the amount of time spent in postures
(bipedal walk, quadrupedal walk, lying, sitting, standing on two feet, standing on four feet, and
praying position) and activities (licking, playing, pulling hair, self-grooming, and touching the
wound). ...