Data from: coyotes can do ‘puppy dog eyes’ too: comparing interspecific variation in Canis facial expression muscles

Facial expressions are critical for non-verbal communication. The Canis
genus epitomizes the interplay between behavior and morphology in the
evolution of nonverbal communication. Recent work suggests that the
levator anguli oculi medialis (LAOM) muscle is unique to dogs (Canis
familiaris) within the Canis genus and evolved due to domestication. The
LAOM raises the inner eyebrows, resulting in the ‘puppy dog eyes’
expression. Here, we test whether the LAOM is a derived trait in dogs by
(1) examining the facial expression muscles of a closely related and
ancestral wild Canis species, the coyote (C. latrans), and (2) comparing
our results to other Canis and canid taxa. We discover that coyotes have a
well-developed LAOM like dogs, which differs from the modified/absent LAOM
in gray wolves. Our findings challenge the hypothesis that the LAOM
developed due to domestication. We suggest the LAOM is a basal trait that
was lost in gray wolves. Additionally, we find inter- and intraspecific
variation in size of the muscles of the outer ear, forehead, lips, and
rostrum, indicating potential adaptations related to sensory perception,
communication, and individual-level functional variations within canids.
Together, this research expands our knowledge of facial expressions, their
evolution, and their role in communication.