Photograph by Independent Picture Service / Universal Images Group via Getty Images
WORDS BY KATARINA ZIMMER
Japanese tits are very polite birds. When mother and father arrive at the nest at the same time, bearing caterpillars to feed their young, one partner will flutter its wings at the other—an “after you” signal encouraging their partner to enter the nest first.
This simple gesture is much more human-like than one might give the little, rotund birds credit for. Rather than merely pointing out objects or directions, “symbolic” gestures like this take on their own meaning—like a goodbye wave—an ability so sophisticated it was long thought to be unique to humans and other great apes, explained Dr. Toshitaka Suzuki, who described the Japanese tits’ behavior in a study last year. “This is the first evidence that birds can use their wings… to convey some unique messages,” he said.
Scientists once believed that only humans were capable of complex communication. Animal interactions, by contrast, were deemed to be largely primitive; messaging was thought to be reflexive and simple, only capable of communicating emotional states to one another. But Suzuki—an “animal linguist” at the University of Tokyo who has studied Japanese tits for nearly 20 years, is learning the birds’ gestures and chirps show many of the same complexities as human language. For one, they appear to convey meaningful things to one another and combine phrases into more complex messages akin to how humans build sentences. Other scientists observed that chimpanzees intentionally communicate about threats to one another, while elephants seem to use name-like calls to address others in their species.
This research on wild birds and mammals opens a window into the rich world of animal communication while challenging long-held views that language evolved only in humans. Scientists are now coming to see language as a constellation of different capabilities that each evolved on the evolutionary tree before our time, granting many other animals unique ways of conversing about their world.
“We’ve [learned] that actually everything we thought was [only] true about human language is actually not that specific to us,” said Dr. Mélissa Berthet, who studies primate communication at the University of Zurich in Switzerland. This research is “definitely changing the game,” she said.
"After you" gesture of the Japanese tit. Courtesy of Toshitaka Suzuki.
One of the biggest challenges in studying animal communication has been distinguishing whether animals are actually conveying meaningful messages to one another or merely sharing information about their emotional states. Many animals, like certain monkeys, apes, meerkats, and birds, use specific alarm calls when they see certain predators. Vervet monkeys, for instance, have different calls for eagles, leopards, and snakes; each triggers a predator-specific response in other monkeys, like scanning the ground for snakes or searching the skies for eagles, explained Berthet, who has studied alarm calls of titi monkeys of South America.
It’s undetermined whether these calls signal fear of particular predators—and trigger reflexive responses—or if the calls are actually intended to mean “there’s a leopard!” The latter might cause receivers to mentally picture a leopard and then reason how to act, like how people would react to the word. What do the animals think?
Suzuki devised a creative way of answering this question. Japanese tits produce a rapid jar jar jar sound when they detect their nemesis, the Japanese rat snake, which ravenously hunts bird eggs and nestlings. The alarm prompts other birds to look down for slithering predators, which they then attempt to drive away from their nests. To work out if the birds actually picture a snake upon hearing the alarm, Suzuki took advantage of the observation that hearing words affects how we see objects; if we hear “cat,” we quickly recognize the feline resemblance of a four-pronged cloud, but if we hear “dog,” we see it as fido instead.
“We’ve learned that actually everything we thought was only true about human language is actually not that specific to us.”
For Japanese tits, Suzuki hung a superficially snake-like object—a short stick—onto a tree. “If the snake-specific alarm calls mean ‘snakes,’” Suzuki reasoned, “they might misrecognize a snake-like object as a real snake”—and look down to inspect the stick.
Sure enough, most birds closely inspected the stick when snake alarm calls played through a speaker—but they didn’t when hearing other kinds of alarm calls and non-alarm calls, Suzuki reported in 2018. Together with other experiments, “these results indicate [that] such snake-specific alarm calls evoke a visual mental image of a snake in Japanese tits’ mind,” Suzuki said, although some linguists disagree with this explanation and argue there are simpler explanations for the birds’ behavior.
What is clearer, however, is that the birds also combine calls using syntactic rules similar to those that people use to order words (for instance, subject–verb–object). When Japanese tits encounter predatory shrike birds, they often combine the alarm call for cats and owls with a flock-gathering “recruitment” call. That rallies other Japanese tits to collectively shoo away the intruder. When Suzuki played a recording of the sequence, the birds scanned the area for shrikes and then approached the speaker—but only when they heard the alarm-recruitment combination in the correct order.
Suzuki took the experiment one step further. He replaced the Japanese tits’ recruitment call with an alarm call from a neighboring species, the willow tit, whose vocalizations Japanese tits can understand. In a remarkable display of comprehension, Japanese tits scanned the horizon and approached the speaker when they heard their own alarm call followed by the willow tit’s recruitment call—but only when Suzuki used the correct order. Evidently, the birds use syntactic rules to understand phrases that are new to them, much like humans, Suzuki said: “If you know neko means cat in Japanese, you can understand ‘I like neko,’ which is a novel sentence for you, but you can use the subject-verb-object rule to understand this.”
Other animals, too, have much more complex communication than once thought possible. Some of the most convincing evidence that communication can be intentional—and not just reflexive—comes from our close relatives, chimpanzees. Though apes are extremely intelligent, it’s been unclear how complex their communication is.
Scientists in 2017 observed that if they played a snake alarm call before a wild chimpanzee encountered a model snake, that individual wouldn’t sound the alarm because it understood that other chimps already knew. In another experiment where orangutan mothers noticed model tigers (humans donning tiger-striped clothes) in their area, they first refrained from producing an alarm sound to avoid drawing attention from the tiger. Only later did they warn their young, demonstrating an ability called displacement—being able to communicate about things that aren’t currently present. The only other nonhuman animals known to be capable of this are honeybees, which use a “waggle dance” to signal the whereabouts of food sources to their hivemates. “For a very long time, it was thought this was only possible in human language,” Berthet said.
Cornell University behavioral ecologist Mickey Pardo and his colleagues discovered in 2024 that elephants, much like dolphins, parrots, and marmoset monkeys, use certain sounds to address specific individuals—effectively calling them by name. Using machine learning algorithms, they found that elephant rumbles known to be addressed to specific individuals contained acoustic patterns that were specific to the recipient (although humans can’t hear this difference, Pardo said). Upon playing recordings back to the elephants, the animals responded much more strongly to calls addressed to them than to other calls, approaching the speaker more quickly and making more vocalizations of their own. The results, Pardo said, “suggest at least that elephants might have a complex mental representation of other individuals in their social group.”
“What’s already clear, though, is that many complex communication abilities are not unique to humans and may actually be quite ancient, given that they occur in distantly related animals like birds and primates.”
And, like Japanese tits, many other animals use specific orders to combine multiple sounds; linguist Dr. Balthasar Bickel of the University of Zurich and his colleagues recently discovered complex patterns in the vocalizations of common marmosets, for instance. The challenge, however, is working out whether these patterns actually mean something to the animals. So far, Suzuki’s research remains the most convincing evidence for meaning in such compositions, but “it’s very limited and it’s only one piece of evidence,” Bickel said. More research like Suzuki’s is needed to untangle what calls, and combinations thereof, actually mean to wild animals, Pardo added.
What’s already clear, though, is that many complex communication abilities are not unique to humans and may actually be quite ancient, given that they occur in distantly related animals like birds and primates. But while each ability may have its own evolutionary history, Bickel suspects all of these communication skills came together in the human lineage to produce our super-complex language. “We were just the lucky ones in evolution that got the combination, in a way,” he said.
It’s also important to note that other animals may have abilities we lack, Suzuki said. Japanese tits, for instance, are born with the ability to recognize certain sounds: knowing to crouch down silently in response to crow alarm calls and to jump out of the nest when they hear snake alarms; whereas humans need to first learn the meaning of sounds. Suzuki sees human language not as singularly special, but just one of many unique communication systems in the animal kingdom with each tailored to the world of the species that speaks it.
This field of research has also ignited a fierce debate about what “language” even is. Until recently, the term was reserved for human communication—but if many of its fundamental characteristics are shared with other animals, then shouldn’t they have “language,” too? For his part, Pardo said he’d define language as a communication system that is capable of expressing virtually any thought or idea—something that, so far, we know only applies to humans. But then again, Pardo said, “we also haven’t necessarily tested if language exists in other species than humans, right?”
While it remains unsettled what makes human language truly unique, one thing humans are singularly capable of is using rigorous science to tap into the communication of other creatures, bringing us closer than any other animal to understanding the lives and worldviews of our neighbors. Suzuki already seems to be on that road. By listening to the chirps and chirrups of Japanese tits, he can detect the presence of hawks and snakes and can predict the birds’ behaviors. At least for some of their vocalizations, he said, “I feel I have developed the ability to understand the meanings.”
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Decoding the Astonishing Secret Languages of Animals
