Meeting Abstract

P3-35   -   Adaptations to sociality and hypercarnivory in the facial muscles of the African wild dog (Lycaon pictus) and coyote (Canis latrans) Smith, HF*; Felix, MA; Rocco, FA; Lynch, LM; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ hsmith@midwestern.edu https://www.midwestern.edu/academics/our-faculty/heather-smith-phd.xml

The cranial musculature of canids has evolved in response to differing selective pressures including sociality and diet, resulting in a considerable variation in the morphology of muscles of facial expression and mastication. We sought to describe the variation in cranial muscles in two canids with disparate life histories: African wild dog (Lycaon pictus) and coyote (Canis latrans). L. pictus is highly social and hypercarnivorous, engaging in sophisticated pack hunting of large game. Communication occurs predominantly through vocalization with reduced reliance on facial expressions. It has large, mobile ears, which enhance its auditory capabilities while hunting and assist with thermoregulation. C. latrans is omnivorous, hunts solitary or in family groups, has modestly sized ears, and exhibits a large range of facial expressions. We performed detailed dissections of muscles of facial expression, mastication, and ear movement in an adult male L. pictus and juvenile male C. latrans specimen, and conducted diceCT scans on L. pictus. All canid species evaluated have well-developed muscles of facial expression and mastication. M. levator anguli oculi medialis (LAOM), a muscle of hypothesized importance in domestic dog-human non-verbal communication, is enlarged in L. pictus, suggesting that ocular facial expressions represent a significant component of communication. Expansions were also noted in muscles that draw the angles of the mouth caudally (mm. zygomaticus, sphincter colli) and close the lips (m. orbicularis oris). In C. latrans, m. platysma is reduced. Muscles of mastication are especially enlarged in L. pictus, with multiple bellies separated by deep layers of thick intermuscular fascia and expanded insertions. Ear muscles are well-developed in L. pictus, supporting greater leverage and fine manipulation of its large, mobile ears.