New research from Baylor University reveals that coyotes, like domestic dogs, have the ability to produce the famous "puppy dog eyes" expression. The study – published in the Royal Society Open Science – challenges the hypothesis that this facial feature evolved exclusively in dogs as a result of domestication.
The research team, led by Patrick Cunningham, a Ph.D. research student in the Department of Biology at Baylor University, examined the levator anguli oculi medialis (LAOM), the muscle responsible for raising the inner eyebrow to create "puppy dog eyes," in coyotes.
Contrary to previous assumptions, Cunningham and colleagues discovered that coyotes also possess a well-developed LAOM, similar to dogs. This finding contradicts the idea that the muscle evolved specifically for communication between humans and dogs during domestication.
“Our findings suggest that the ability to produce ‘puppy dog eyes’ is not a unique product of dog domestication but rather an ancestral trait shared by multiple species in the Canis genus,” Cunningham said. “This raises fascinating questions about the role of facial expressions in communication and survival among wild canids.”
Coyotes, dogs and gray wolves comparisons
Cunningham and his team compared the facial muscles of coyotes, dogs and gray wolves. While both dogs and coyotes possess a well-developed LAOM, the muscle is either modified or absent in gray wolves. This challenges the hypothesis that human-driven selection was solely responsible for the development of the inner brow raiser in dogs. Instead, the study suggests that the LAOM was likely present in a common ancestor of dogs, coyotes and gray wolves but was later lost or reduced in wolves.
The research also documented significant intraspecific variation in the facial muscles of coyotes, particularly those related to brow and lip movements. Genetic analysis was used to rule out significant dog ancestry in the coyote specimens, reinforcing that these traits are not a result of crossbreeding.
“Our work reveals that coyotes and dogs share not just behavioral similarities, but also a fascinating evolutionary history that includes the ability to make expressions that we once thought were unique to domesticated animals,” Cunningham said.
This discovery has broader implications for understanding the evolution of facial expressions in mammals. The LAOM may have originally evolved for functions related to vision and eye movements, rather than communication with humans, as previously thought. Future studies on other canid species, including red wolves and African wild dogs, may further illuminate the role of facial expressions in survival and species communication.
This work was supported through a grant from the National Institute of Food and Agriculture, U.S. Department of Agriculture McIntire-Stennis Program under award number 1027755 and Michigan Technological University REF R01787.
The research team included:
- Patrick Cunningham, Ph.D. student with the Department of Biology and member of the Comparative Ecophysiology of Animals Lab (CEAL) at Baylor University.
- Sarah S. Kienle, Ph.D., assistant professor in the Department of Biology and director of the CEAL lab at Baylor University.
- Mahita Shankar, undergraduate student with the Department of Biology and member of the CEAL Lab at Baylor University.
- Bridgett vonHoldt, Ph.D., associate professor with the Department of Ecology & Evolutionary Biology at Princeton University.
- Kristin E. Brzeski, Ph.D., associate professor with the College of Forest Resources and Environmental Science at Michigan Technological University.
ABOUT THE COMPARATIVE ECOPHYSIOLOGY OF ANIMALS LAB
The (CEAL) at Baylor University focuses on understanding how different animals work in the context of their environment. Researchers use quantitative analytical techniques to examine physiological and ecological factors that shape mammalian life history strategies.
Research in this lab falls into three themes:
- Characterizing relationship between animal form and function.
- Comparing trade-offs between different life history strategies.
- Examining flexibility in ecophysiological traits.
ABOUT BAYLOR UNIVERSITY
Baylor University is a private Christian University and a nationally ranked Research 1 institution. The University provides a vibrant campus community for more than 20,000 students by blending interdisciplinary research with an international reputation for educational excellence and a faculty commitment to teaching and scholarship. Chartered in 1845 by the Republic of Texas through the efforts of Baptist pioneers, Baylor is the oldest continually operating University in Texas. Located in Waco, Baylor welcomes students from all 50 states and more than 100 countries to study a broad range of degrees among its 12 nationally recognized academic divisions. Learn more about Baylor University at .
ABOUT THE COLLEGE OF ARTS & SCIENCES AT BAYLOR UNIVERSITY
The College of Arts & Sciences is Baylor University’s largest academic division, consisting of 25 academic departments in the sciences, humanities, fine arts and social sciences, as well as 11 academic centers and institutes. The more than 5,000 courses taught in the College span topics from art and theatre to religion, philosophy, sociology and the natural sciences. The College’s undergraduate Unified Core Curriculum, which routinely receives top grades in national assessments, emphasizes a liberal education characterized by critical thinking, communication, civic engagement and Christian commitment. Arts & Sciences faculty conduct research around the world, and research on the undergraduate and graduate level is prevalent throughout all disciplines. Visit the .
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