Because we learn to speak from nearby adults, our dialects diverge across geographic boundaries. It is even possible to predict where a stranger was raised based solely on speech patterns. Southerners, for example, use “y’all” as the preferred plural of “you”, while South Philadelphians say “you.” People from different eras also speak differently; you’d get weird looks if you walked around talking like Shakespeare.
But we’re far from the only species that has a range of vocal patterns. Sac-winged bats, for example, live across Mexico and South America and have vocal styles in this range. When female bats disperse to mate, they listen for similar calls — enough to indicate familiar foods and pathogens — but not identical to the group they were born into. Similarly, in California, white-crowned sparrows living within a few miles of each other often sing different tunes; in rare cases, individuals living at the borders between populations may even become bilingualswitching code between dialects to match their environment.
In addition to dialects, these vocal learners also share other human vocal patterns: they babble like babies and even change their pronunciation over time. The similarities “let’s look at processes that may be similar to human cultural change,” says Julia Hyland Bruno, an incoming assistant professor at the New Jersey Institute of Technology who studies songbirds. Since it is difficult to experiment with human voice learning ethically, these model systems are powerful – albeit simplified – mirrors of the development and evolution of our own culture.
Human babies babble. Before their first birthday, in fact, most of them already produce “protophones” precursors of speech. Infants produce approximately 3,500 protophones per day, even if no one is listening. It’s probably a way for them to perform and explore their vocal repertoire.
Songbird chicks also vocalize in a manner that resembles babbling. Some species producesub-songwhich eventually turns into an adult song. Charles Darwin noticed it in 1871 when he wrote that an early song “can be compared to a child’s imperfect effort to babble”.
Same baby babbling bats. Sac-winged bats rhythmically repeat adult syllables and nonsense proto-syllables – like a baby’s “ba-ba-ba.” It’s spontaneous and adults don’t pay attention to it, says Mirjam Knörnschild, a behavioral ecologist at the Natural History Museum in Berlin. When not sleeping, baby bats (called pups) spend 30% of their time babbling. “They have this very British way of them,” says Knörnschild, referring to the way they take turns without interrupting each other.
The little sac-winged bat. (Credit: Mendesbio/Shutterstock)
If you venture into the forest, she adds, there are so many gossips that you can’t miss them. Like humans, babble pups train for later vocalizations, but Knörnschild thinks they might also play: “I’m really curious if our bats feel better when they babble.”
Songbirds go viral
During the Large vowel shift from the 15th to the 18th century, English speakers began to pronounce higher vowels in their mouths. Before that, they pronounced “bite” as “beet”, “beet” as “bait”, and “bait” as “bot”. The speed of change was amazing. Word choice and grammar can change even more than pronunciation. By analyzing interactions on Twitter, researchers valued that for every 100 words we read, we start using one more frequently. Sure, grammar rules and slang evolve even faster than that.
Like humans, bird vocalizations also change over time. White-throated sparrows, for example, usually sing songs that end in a triplet. (Ornithologists identify it as the Oh sweet Canada, Canada song.) But in the early 2000s, birds from Prince George, British Columbia began sing a new song which ended with a doublet: Oh sweet cana cana cana.
“It’s audibly different,” says Scott Ramsay, an associate professor at Wilfrid Laurier University who studied the new song. He was amazed when he discovered in 2002 that all birds in Prince George sing the doublet song, but birds in eastern Ontario never sing it. Researchers confirmed this on a road trip from British Columbia to Alberta: The further east they went, the less common doublet song became, Ramsay says.
White-throated sparrow. (Credit: Mircea Costina/Shutterstock)
But over the next two decades, the song went viral. In 2019, birds from coast to coast were singing the cana adjust. Eastern birds probably picked it up from shared wintering grounds in Texas and brought it back to Ontario to teach their chicks. Ramsay isn’t sure why the song stuck — maybe the beat is easier, he guesses. Now he and his colleagues are tracking down a third song emerging in western Canada. “It reproduces,” he says, “and it spreads.”
In humpback whales, the change in song was even faster – so fast that the researchers called it a cultural revolution. Eastern and Western Australian whales generally sing different songs; but between 1995 and 1996, two debutants came to the east singing the tune from the west. The song spread like wildfire, and in 1998 every whale sang the new song.
In the years that followed, cultural transmission from west to east repeated itself – not just in Australia, but across the Pacific Ocean. The whales transmitted songs for nearly 5,000 miles. Pods from French Polynesia sang tunes that were popular in American Samoa a year earlier, which they picked up in Australia the previous year. Like the Great English Vowel Shift, the speed and scale of change was staggering.
Humpback whales. (Credit: Maui Topical Images/Shutterstock)
Across time scales – from the babbling childhood of a bat to the generational changes of whale songs – vocal culture in animals parallels human speech. These similarities allow for “experimentation in the emergence of vocal culture”, said Hyland Bruno. “We control social interactions…and then let the animals freely show us how they react.”
Read more: How does your dog understand you?
Comparisons are not perfect; no one handles language like humans. But the study of animal voice culture can highlight unifying principles of learning that we all share.