title: Facial expression: An under-utilised tool for the assessment of welfare in mammals.
abstract: Animal welfare is a key issue for industries that use or impact upon animals. The accurate identification of welfare states is particularly relevant to the field of bioscience, where the 3Rs framework encourages refinement of experimental procedures involving animal models. The assessment and improvement of welfare states in animals depends on reliable and valid measurement tools. Behavioral measures (activity, attention, posture and vocalization) are frequently used because they are immediate and non-invasive, however no single indicator can yield a complete picture of the internal state of an animal. Facial expressions are extensively studied in humans as a measure of psychological and emotional experiences but are infrequently used in animal studies, with the exception of emerging research on pain behavior. In this review, we discuss current evidence for facial representations of underlying affective states, and how communicative or functional expressions can be useful within welfare assessments. Validated tools for measuring facial movement are outlined, and the potential of expressions as honest signals is discussed, alongside other challenges and limitations to facial expression measurement within the context of animal welfare. We conclude that facial expression determination in animals is a useful but underutilized measure that complements existing tools in the assessment of welfare.
authors.affiliation: Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom.|Environmental and Animal Sciences, Unitec Institute of Technology, Auckland, New Zealand.|Centre for Animal Welfare and Ethics, University of Queensland, St Lucia, Australia.
authors.forename: Kris A
authors.initials: KA
authors.lastname: Descovich
authors.affiliation: School of Psychology, University of Sussex, Brighton, United Kingdom.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wathan
authors.affiliation: School of Agriculture, Food & Rural Development, University of Newcastle, Callaghan, Australia.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Leach
authors.affiliation: Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Buchanan-Smith
authors.affiliation: Comparative Biology Centre, University of Newcastle, Callaghan, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Flecknell
authors.affiliation: Centre for Macaques, Medical Research Council, Salisbury, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Farningham
authors.affiliation: Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom.
authors.forename: Sarah-Jane
authors.initials: SJ
authors.lastname: Vick
mesh_terms: D000827:Animal Welfare; D000818:Animals; D005149:Facial Expression; D006801:Humans; D008322:Mammals
keywords:  animal welfare;  communication;  refinement; emotion; facial expressions