Study identifies subtle facStudy identifies subtle facial cues that help keep harmony within the packial cues that help keep harmony within the pack
When wolves are tumbling, nipping, and baring their fangs at one another, it could mean an all-out brawl is brewing—or simply be a bit of playful roughhousing. So how do the carnivores know what their comrades are thinking before it’s too late?
According to a new study in Animal Behaviour, subtle facial cues help wolves signal their intentions. This facial communication isn’t just good manners—it helps maintain cohesion within the pack.
“These [facial expressions] … say ‘hey we’re playing now, and it’s just for fun,’ or ‘now, it’s actually for real,’” says Christina Hansen Wheat, an ethologist at Stockholm University who was not involved with the study. “It’s a very fine-tuned communication tool.”
Most research into wolves’ facial expressions is decades old and purely observational. Many contemporary studies have used methods designed to study dogs—a poor proxy, as our furry friends have fewer facial expressions than their ancestors.
So, Veronica Maglieri, an ethologist at the University of Pisa, and colleagues took a closer look at wolves. But not wild ones, as observing any behavior in the wild consistently is challenging. Instead, they habituated captive gray, arctic, and Canadian wolf packs to their presence as the wolves roamed forested enclosures half the size of a soccer field. They sat just outside the enclosures for hours at a time. “We used the first week just to learn how to recognize every single wolf,” Maglieri says. Identifying them in the middle of a fight or in harsh weather could be otherwise difficult. Eventually, the team could spot individual wolves not only by their faces, but also by the way they walked and the sounds they made, she says. “It was very amazing.”
After the wolves grew comfortable with the researchers after about a week, the team began to take video, attempting to capture every one of the animals’ playful and aggressive interactions with one another as they roamed the enclosure. After recording 135 hours of footage, the researchers caught 379 such interactions on film. Analyzing the footage frame by frame, they looked for individual muscle movements in the wolves’ faces. (These techniques have previously been used to study facial expressions in cats.)
Next, the researchers looked to other cues, such as whether an individual gave its opponent the opportunity to counterattack, to categorize each interaction as either friendly or combative.
The team found five distinct facial expressions that wolves use to communicate different levels of playfulness and aggression. During playful interactions, for example, wolves open their mouths and relax their lips. If play-fighting goes a step too far, the wolf may pull back its lips, revealing its gums and narrowing its eyes. If things continue to intensify and look to boil over into an all-out fight, the wolf will reveal a light spot on the very top of its gums: a blazing red warning flag. These expressions were common to all of the gray, arctic, and Canadian wolf packs the researchers observed.
The differences between the expressions are subtle but critical, notes study co-author Elisabetta Palagi, an ethologist at the University of Pisa. “A few key elements change the meaning.”
“I like the essence of the paper,” Hansen Wheat says. “And I think it’s important that we have more studies on wolves out there.”
In the future, Maglieri and Palagi want to investigate why domestic dogs’ facial expression repertoire has become more simplified. One theory is that having fewer expressions means there’s less potential for confusion between dogs and their human companions. “If you want to communicate with another species, the best solution is to always use the same [simple] facial expression,” Maglieri says, rather than multiple more subtle ones.
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