As the millions of views that videos of animals dubbed over with human voices can attest, people seem to love nothing more than anthropomorphizing our non-human counterparts in nature. These videos might make us giggle, but what about the creatures that star in them, can they laugh?
The answer, according to a new paper studying animals at play, may be yes—to the tune of some 65 species that researchers pegged as “laughing” during bouts of playful activity, reports Mindy Weisberger for Live Science.
“This work lays out nicely how a phenomenon once thought to be particularly human turns out to be closely tied to behavior shared with species separated from humans by tens of millions of years,” says Greg Bryant, a cognitive scientist at the University of California, Los Angeles and co-author of the study, in a statement.
Most of the 65 species identified by the study, which was published last month in the journal Bioacoustics, were mammals, such as primates, foxes, killer whales and seals, but three bird species also made the list, according to the statement.
For animals, the researchers suggest, a laughing noise may help signal that roughhousing, or other behavior that might seem threatening, is all in good fun.
“[Some actions] could be interpreted as aggression. The vocalization kind of helps to signal during that interaction that 'I'm not actually going to bite you in the neck. This is just going to be a mock bite,'” Sarah Winkler, an anthropologist at the University of California, Los Angeles and the paper’s lead author, tells Doug Johnson of Ars Technica. “It helps the interaction not escalate into real aggression.”
Winkler witnessed firsthand that vocalizations often accompany animals playing during past work with rhesus macaques, which pant while they play, according to Live Science. To find out how widespread such play vocalizations might be in the animal kingdom, Winkler and Bryant scoured the scientific literature for descriptions of play activity in various animals. In particular, the study authors looked for mentions of vocalizations accompanying playtime.
Per Ars Technica, many of the animal laughs identified by the study sound nothing like a human chuckle. For example, Rocky Mountain elk emit a kind of squeal and, per Live Science, New Zealand’s kea parrot whines and squeaks when it’s time to have some fun.
Back in 2017, another study found that playing a recording of kea laughter around the parrots in the wild would cause the birds to spontaneously break into playful tussles.
Another key difference between human and animal laughter could be its volume and thus its intended audience, according to Live Science. Human laughs are pretty loud, so the whole group can hear, but most animals, by contrast, have laughs that are quiet and may only be audible to the play partner. (By the study's definition, cats hissing during playtime qualified as laughter.)
Winkler tells Ars Technica that though the study aimed to be comprehensive, that there may be even more laughing animals out there. “There could be more that, we think, are out there. Part of the reason they probably aren't documented is because they're probably really quiet, or just [appear] in species that aren't well-studied for now,” she says. “But hopefully there could be more research in the future.”