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Raising an Eye at Facial Muscle Morphology in Canids
Courtney L Sexton1,2, Rui Diogo3, Francys Subiaul2,4
1Department of Population Health Sciences, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Biology
|May 24, 2024
Summary
Dog facial muscles, like the levator anguli occuli medialis (LAOM) and retractor anguli occuli lateralis (RAOL), linked to human-directed communication, are not unique to domesticated dogs. This suggests these traits may not solely result from human breeding.
Area of Science:
- Comparative Anatomy
- Animal Behavior
- Evolutionary Biology
Background:
- Facial muscle evolution in dogs is associated with human selection for traits communicating emotion.
- Dogs exhibiting perceived helplessness, particularly through eye expressions, can trigger human caregiving responses.
- The specific facial muscles (levator anguli occuli medialis and retractor anguli occuli lateralis) involved in these expressions may not be exclusive to domestic dogs.
Purpose of the Study:
- To investigate the presence of specific facial muscles (LAOM and RAOL) in various canid species.
- To determine if these muscles, implicated in human-directed canine communication, are unique to domesticated dogs (Canis familiaris).
Main Methods:
- Preliminary, qualitative gross anatomical evaluation.
- Examination of 10 canid specimens across different species.
Main Results:
- The study found that the levator anguli occuli medialis (LAOM) and retractor anguli occuli lateralis (RAOL) muscles were present in non-domesticated canid species, not just Canis familiaris.
- This indicates that these muscles are not exclusively found in domesticated dogs.
Conclusions:
- The presence of LAOM and RAOL muscles in various canids suggests they do not necessarily reflect selection solely through human domestication and breeding.
- Future research should include quantitative analyses of more canid species and investigate the impact of superficial facial features on canine and interspecies communication.
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