Coyotes Might Make ‘Puppy Eyes,’ Suggesting the Facial Expression Evolved for More Than Just Cuteness

The adorable “puppy dog eyes” expression has long been associated with our canine companions. Researchers have thought the wide-eyed look evolved due to humans’ close bond with dogs and their history of domestication. Now, a new discovery sheds light on how other wild canines might share the same skill, making scientists rethink our history with dogs.

A new study published Wednesday in Royal Society Open Science suggests the facial muscles needed for the “puppy dog eyes” expression might not be exclusive to domestic dogs. Coyotes have the same well-developed muscle, researchers report, although the reason behind its presence is unclear.

The finding suggests this trait might be an ancestral one shared by multiple canine species, Patrick Cunningham, a researcher at Baylor University, says in a statement. “This raises fascinating questions about the role of facial expressions in communication and survival among wild canids.”

Big, pleading “puppy dog eyes” come from the use of a facial muscle called the levator anguli oculi medialis, or LAOM. The muscle works by raising the inner eyebrow to create especially large-looking eyes.

People can mimic the heart-melting look in a similar way. “You’re not changing the shape of your eyeball—you’re just making them appear bigger,” Sarah Kienle, a comparative biologist at Baylor University and a co-author of the study, tells Science News’ Susan Milius.

To examine the iconic facial expression in canines, Cunningham and his team collected and dissected ten coyotes that had been previously killed by vehicles or hunters, as well as the donated remains of an Australian cattle dog. Then, they compared the LAOM muscles of coyotes, dogs and gray wolves.

They found that both dogs and coyotes have a well-developed LAOM, while previous work found this muscle is either modified or missing in gray wolves. The result challenges the hypothesis that the LAOM evolved as part of the emotional bond between humans and dogs, and instead indicates it was present in a common canine ancestor.

“We always think, ‘certainly the dog is the unique species here,’ but they’ve made a really nice claim that maybe it’s the wolf that’s the unique species,” says Anne Burrows, a biological anthropologist at Duquesne University who wasn’t involved in the study, to Science’s Jason Bittel. Perhaps wolves lost the LAOM muscles because they communicate mainly through long-distance vocalizations, she adds.

After the dissections, the authors used genetic analysis to rule out that their examined coyotes had dog ancestry. This helped the team be sure the observed muscles did not come from crossbreeding.

Since 2019, researchers have hypothesized about how this endearing trait evolved in canines. The new study adds to a growing body of research indicating the expression did not evolve solely in domestic dogs. A study published in April, for example, found African wild dogs also have the “puppy eyes” muscle.

For other canines, the LAOM may have evolved for functions related to eye movements and vision, rather than for communication, the researchers say in the statement.

The discovery “changes the conversation,” Kienle tells Science News. The expressive skill of the so-called puppy eyes seems “potentially more an ancestral trait rather than something that’s evolved as part of this dog-human relationship,” she adds.

This finding has wider significance for understanding the evolution of facial expressions in canines—and in mammals more generally. According to the statement, future studies on other canines, including red wolves and African wild dogs, “may further illuminate the role of facial expressions in survival and species communication.”

Alexa Robles-Gil | | READ MORE

Alexa Robles-Gil is a bilingual science journalist based in New York City. Her work has appeared in the Guardian, Undark, Inside Climate News and more.