DOI: 10.5061/dryad.3j9kd51rk
title: Data from: coyotes can do ‘puppy dog eyes’ too: comparing interspecific variation in Canis facial expression muscles

description: 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.
description: <em>Sample Collection</em>. We opportunistically
 collected nine coyotes (5 males, 3 females, 2 unknown sex) and one dog
 (male, Australian cattle dog; Table 1) to examine their muscles of facial
 expression under Texas Parks and Wildlife scientific collections permit
 number SPR-1221-200. All but one of our coyote specimens (BU008) were
 collected in McClennan and Galveston counties, Texas. BU008 was donated
 from a sportsman in Fayette county, Texas.  The dog was donated from
 Central Texas Humane Society in Waco, Texas. All specimens were adults
 based on age estimates from tooth wear. Prior to the dissection, the head
 was separated from the body at the base of the occipital condyle. We took
 a small tissue sample from the tongue, ear, or temporalis for genetic
 analysis. All specimens were in good condition (i.e., fresh dead with
 little to no muscle decomposition) and kept frozen in a -20℃ freezer until
 dissection.  <em>Dissections.</em>
 Specimens were dissected fresh without any chemical fixation. Prior to
 beginning each dissection, we took scaled photographs of the dorsal,
 ventral, and lateral sides of the head. For roadkill specimens, we noted
 any obvious fractures of the cranium or mandible that may have altered the
 shape of the superficial musculature. We did not include any specimens
 where the skull or musculature was determined to be in poor condition. We
 started each dissection with a rostro-caudal incision from the base of the
 nose pad to the occipital protuberance. The skin was separated from the
 superficial layer of muscle on the left lateral aspect of the head to
 allow for examination of the superficial muscles of facial expression. 
 Next, we removed the superficial musculature to reveal the deeper facial
 musculature. For each muscle, we took scaled photographs, described the
 muscle insertion, origin, fiber direction, and action, and noted any
 interspecific and intraspecific variation in musculature.
 We documented the presence, absence, or reduction of each muscle
 in the coyotes and dog that we dissected. We referred to Kaminski et al.
 (2019) for gray wolf anatomy, and we verified our dog findings with
 reference to Evans and de Lahunta, (2013); this enabled comparisons among
 the three taxa. 
description: # Data from: coyotes can do ‘puppy dog eyes’ too: comparing interspecific
 variation in Canis facial expression muscles
 [https://doi.org/10.5061/dryad.3j9kd51rk](https://doi.org/10.5061/dryad.3j9kd51rk) Each folder contains scaled photographs of the coyote and dog specimens used in this study, labeled based on the specimen ID. Photographs are from dissections of the muscles of facial expression. Dissections were performed in a biosafety cabinet.  ## Description of the data and file structure All photographs within a file are of the specimen identified in the file name. Images are raw photographs. In some photographs, anatomical structures are numbered to aid in identification.   ## Sharing/Access information ## Code/Software There is no code associated with these photographs