Dogs and horses may not be the most intuitive teammates, but paired up in the right setting, the two domesticated species can have their fair share of fun—at times even playing together and mimicking each other’s facial expressions, new research suggests.
These findings, published in the journal Behavioural Processes, mark the first instance of so-called rapid facial mimicry occurring between play partners of different species, and hint at the existence of a universal language of play, reports Virginia Morrell for National Geographic.
Though the purpose behind play remains unclear, scientists suspect the behavior arose to help animals hone hunting and social skills, relieve stress or foster relationships with each other, study author Elisabetta Palagi, an animal behaviorist at the University of Pisa in Italy, tells Charles Q. Choi at Inside Science. Learning more about the contexts in which different creatures pal around—especially across branches of the tree of life—could tell researchers a lot about play’s origins and evolution. But apart from a handful of studies featuring humans and their pets, scientists haven’t had many chances to analyze examples of interspecies romps.
In 2018, when someone sent Palagi a YouTube video featuring a dog and horse playing together, seemingly in sync, she leapt at the chance to investigate further. The two species, she noted early on, were especially good candidates for interspecies camaraderie, because they’ve both been shown to recognize facial expressions in other animals. Marshalling a team of research students, Palagi began to amass and analyze hundreds of other clips with canines and equids partnering in play.
Screened for strict criteria, only 20 videos ended up meeting the team’s requirements: showing animals freely playing on their own, without human interference, for at least 30 seconds.
Several common themes quickly arose. Engaged in play, dogs and horses often mirrored each other’s moves, jumping, pushing and even nipping mischievously at each other. They also put themselves in vulnerable positions, such as rolling on their backs, displaying their throats and stomachs—a strong sign that they were at ease and even communicating their friendly intentions, according to Inside Science.
Despite millions of years of evolution between them, the two species seemed to take the same basic approach to frivolity, suggesting that they’d found common ground for the sole purpose of fun, Palagi tells Inside Science.
The two creatures also frequently imitated each other’s facial expressions, both adopting the relaxed, open mouths—a behavior that’s been noted in wild, social primates, but never between a pair of animals of different species.
Horses and dogs may look and behave in immensely different ways, Barbara Smuts, a behavioral ecologist at the University of Michigan who wasn’t involved in the study, tells National Geographic. But fun is perhaps a language that doesn’t need to be taught. Two vastly dissimilar creatures, Smuts says, can still “negotiate how to play in a way that’s comfortable for both.”