(Credit: ROBERT ENRIQUEZ/Shutterstock)
WACO, Texas — In a surprising twist that challenges our understanding of canine evolution, researchers have discovered that coyotes possess the same facial muscle responsible for the irresistible “puppy dog eyes” expression seen in our beloved pet dogs. This finding suggests that the ability to make this endearing face is not unique to our four-legged companions but may be a trait shared across many species in the Canis genus.
The study, conducted by researchers at Baylor University and published in the journal Royal Society Open Science, focused on examining the facial muscles of coyotes and comparing them to those of dogs and grey wolves. Their most intriguing discovery was the presence of a well-developed levator anguli oculi medialis (LAOM) muscle in coyotes. This small but powerful muscle is responsible for raising the inner eyebrow, creating the heart-melting expression we often associate with pleading dogs.
“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,” explains Patrick Cunningham, a Ph.D. research student in the Department of Biology at Baylor University, in a media release. “This raises fascinating questions about the role of facial expressions in communication and survival among wild canids.”
Previously, scientists believed that early humans selectively bred wolves into the diverse array of dog breeds we see today and that we inadvertently favored those with more expressive faces. This new study, however, turns that theory on its head.
By identifying the LAOM in coyotes, a species that split from the wolf-dog lineage millions of years ago, the researchers suggest that this facial feature is likely a primitive trait. In other words, the ability to make “puppy dog eyes” may have been present in the common ancestor of all these canine species rather than being a recent development in dogs.
“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 adds.
Interestingly, while both coyotes and dogs possess this muscle, it appears to be modified or absent in grey wolves. This unexpected finding raises new questions about the evolutionary history of canine facial expressions and their role in communication, both within species and potentially with humans.
The study didn’t stop at just identifying the presence of the LAOM. The researchers also examined 17 other facial muscles in coyotes, comparing them to those found in dogs and wolves. While many of these muscles were similar across species, they noticed some intriguing differences. For instance, coyotes had smaller versions of certain muscles responsible for ear movement and forehead wrinkling compared to dogs.
These variations in muscle size and development could impact how different canine species express themselves and interact with their environment. For example, the researchers speculate that the reduced size of the muscle-stabilizing coyote ears might allow for quicker ear movements, potentially helping them locate small prey in dense forests.
The study also revealed interesting variations within the coyote population itself. Some muscles, including the one creating puppy dog eyes, showed notable differences in size and shape between different coyotes. These variations within the species hint at the complex connection between genetics, behavior, and anatomy in shaping facial expressions.
As we continue to unravel the mysteries of canine evolution, this study opens up new avenues for research. It raises intriguing questions about the role of facial expressions in wild dog communication and behavior. Could coyotes be using their expressive eyebrows to communicate with each other in ways we haven’t yet recognized? Also, what could this mean for our understanding of how dogs use facial expressions to interact with humans?
Paper Summary
Methodology
The researchers examined the facial muscles of nine coyote specimens, comparing them to those of a domestic dog and previously published data on grey wolves. They carefully dissected and measured each facial muscle, calculating the ratio of muscle size to overall head size to account for differences in body size between individuals. They also analyzed the genetic ancestry of four coyote specimens to ensure their findings weren’t influenced by potential dog or wolf ancestry.
Key Results
The study found that coyotes possess all 18 facial muscles found in dogs, including the well-developed LAOM responsible for raising the inner eyebrow. Some muscles, such as those involved in ear and forehead movement, were smaller in coyotes compared to dogs. The researchers also observed variations in muscle size and shape between individual coyotes.
Study Limitations
The study had a relatively small sample size of nine coyotes and one dog, which may not fully represent the diversity within each species. Additionally, the coyote specimens came from a region with known genetic admixture between coyotes and other canids, which could potentially influence the results.
Discussion & Takeaways
The presence of the LAOM in coyotes suggests that “puppy dog eyes” may be a primitive trait in the Canis genus rather than a result of dog domestication. This finding challenges previous assumptions about the evolution of canine facial expressions and opens up new areas for research into wild canid communication and behavior. The study also highlights the importance of considering genetic admixture when studying morphological traits in canids.
Funding & Disclosures
The study was supported by a grant from the National Institute of Food and Agriculture, U.S. Department of Agriculture McIntire-Stennis Program. The researchers declared no competing interests.
