Raising an Eye at Facial Muscle Morphology in Canids.

Simple Summary: Facial expressions are important for many animals when communicating with other individuals both within and outside of their own species or group. The canid family includes several species that are highly social. Dogs, in particular, have adapted, through domestication, facial expressions that aid in their social interactions with people. The presence of certain facial muscles facilitates these interactions, however it does not seem that these muscles are unique to dogs, but also present in other canids. The evolution of facial muscles in dogs has been linked to human preferential selection of dogs whose faces appear to communicate information and emotion. Dogs who convey, especially with their eyes, a sense of perceived helplessness can elicit a caregiving response from humans. However, the facial muscles used to generate such expressions may not be uniquely present in all dogs, but rather specifically cultivated among various taxa and individuals. In a preliminary, qualitative gross anatomical evaluation of 10 canid specimens of various species, we find that the presence of two facial muscles previously implicated in human-directed canine communication, the levator anguli occuli medialis (LAOM) and the retractor anguli occuli lateralis (RAOL), was not unique to domesticated dogs (Canis familiaris). Our results suggest that these aspects of facial musculature do not necessarily reflect selection via human domestication and breeding. In addition to quantitatively evaluating more and other members of the Canidae family, future directions should include analyses of the impact of superficial facial features on canine communication and interspecies communication between dogs and humans. [ABSTRACT FROM AUTHOR]