SMART NEWS

Wild Dogs Have Muscles for ‘Puppy Eyes,’ Suggesting the Cute Expression Did Not Evolve Just for Humans

African wild dogs have the same well-developed eye muscles that domestic dogs use to make their signature pleading faces, a recent study finds

Sarah Kuta

Daily Correspondent

Two African wild dogs in the grass
African wild dogs might use facial expressions to communicate with each other as they hunt in packs on the savanna. Arno Meintjes via Flickr under CC BY-NC-SA 2.0 DEED

Puppy-dog eyes are irresistible. Many dogs have mastered this iconic, sad-sweet expression, which they use to look up at their human owners while begging for treats or asking to hop onto the furniture.

But pet dogs are not the only canines capable of pleading with their eyes, new research suggests. African wild dogs (Lycaon pictus), also known as painted dogs, have the same well-developed muscles around their eyes as their domesticated cousins do, according to a paper published last month in The Anatomical Record.

The new findings contradict earlier research that suggested dogs may have developed stronger facial muscles to better communicate with humans as they evolved alongside us.

A 2019 study, for example, compared the eye muscles and behaviors of wolves and domesticated dogs. It found that dogs had more highly developed muscles around their eyes and moved their eyebrows more often and with more intensity than wolves did; dogs also made some high-intensity eyebrow movements not observed among wolves. The authors suggested this meant humans had selected for dogs with emotive eyes.

Then, a 2022 study built upon that work and found that dogs had more fast-twitch fibers in their facial muscles compared to wolves. Researchers noted that dogs have a similar proportion of fast-twitch facial muscles as humans do, indicating they might have adapted to win us over.

But are puppy-dog eyes solely the result of domestication? That’s the question the team behind the latest study set out to answer.

To do so, they focused on African wild dogs, which are highly social animals that live and hunt in packs on the African savanna. These creatures weigh between 40 and 79 pounds, and they have large, rounded ears that stick straight up. Their painted dog nickname comes from their distinctive fur, which grows with splotches of black, brown, tan and white—as though someone splattered paint on them.

Researchers dissected a deceased adult male African wild dog from the Phoenix Zoo. They found well-developed facial and ear muscles—and they spotted the two types of eye muscles used for creating puppy-dog eyes. These were similar in size to the ones found in domestic dogs.

The discovery “kind of debunks the idea that domestic dogs are the only canids that have this, and that they evolved specifically for us,” says study lead author Heather Smith, an anatomist at Midwestern University, to Live Science’s Joanna Thompson.

Having more highly developed facial muscles makes sense in the context of African wild dogs. These creatures roam the open savanna together in search of prey. They probably use their eye muscles to make facial expressions as a form of silent communication with each other while hunting, per Live Science.

Wolves, meanwhile, also hunt in groups, but they typically inhabit environments with more visual obstacles, like trees and boulders, which would make it harder for individuals to see each other’s faces. Under those circumstances, sounds and scents may be more effective means of communicating. Perhaps, the researchers speculate, multiple types of canines evolved to have these muscles, and wolves just lost them over time.

Still, not everyone is convinced by the new findings. For instance, while African wild dogs seem to have highly developed muscles around their eyes, that doesn’t necessarily mean they use them in the same way that domestic dogs do.

“Just because the anatomy is there, is it being used?” says Muhammad Spocter, an anatomist at Des Moines University who was not involved in the research, to Nature News’ Gillian Dohrn. “And how is it being used?”

In the future, scientists hope to further explore this question with other wild canines, such as foxes and Asian wolves.

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Sarah Kuta

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.