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In a novel example of vocal learning, chimpanzees picked up what might be considered the equivalent of a Scottish accent after they were moved from a Dutch zoo to Edinburgh.
"It's the first time we've seen another primate species — not humans — change the structure of the call that they gave for a specific object by soclally learning it," University of York psychologist Katie Slocombe told NBC News. Slocombe and her colleagues reported the phenomenon Thursday in the journal Current Biology.
The specific object in this case is an apple, one of the chimps' favorite foods. They typically give out a series of grunts when they see apples, or are eating apples. But chimps from the Beekse Bergen Safari Park in the Netherlands use high-pitched grunts, while chimps from the Edinburgh Zoo in Scotland use a lower pitch.
In 2010, nine chimps from the Dutch zoo were due to be moved to the Scottish zoo for breeding purposes, and that provided a golden opportunity to find out whether chimps, like humans, learn a new lingo when they fall in with a new social group.
The researchers recorded the calls made by the Dutch chimps as well as the Scottish chimps before the move. They followed up with a new set of recordings during the chimps' getting-to-know-you phase in 2011, and after the two groups were fully blended together in 2013. Slocombe and her colleagues found that the Dutch visitors changed their call for apples to conform with the pitch pattern used by their Scottish hosts.
Social connections play a part
The key to the switchover wasn't simply being exposed to the different call in a new environment. Instead, the researchers said the change took hold only after "strong social relationships had formed" between the two groups.
So why did the Dutch chimps change to accommodate the Scottish chimps, rather than vice versa? Were the Dutch chimps merely following the lead of the combined groups' dominant male, an Edinburgher? The researchers say previous studies of wild vervet monkeys point to a different reason.
"An alternative is that conformity mechanisms may have motivated the immigrants to adopt the vocal norms of the host group," they wrote.
More studies will be needed to nail down the full explanation. "It would be really exciting to try and find out why chimpanzees are motivated to sound more similar to their group mates," the University of Zurich's Simon Townsend, another one of the study's co-authors, said in a news release. "Is it so that they can be better understood? Or is it just to sound more similar to their friends?"
The long tale of chimp communication
Previous studies have shown that chimps are quite capable of social learning when it comes to communication. "The results reported here are not surprising in light of these previous findings," Jared Taglialatela, a primate researcher at Kennesaw State University who led one of those studies, told NBC News in an email.
Taglialatela said this week's report provides a clearer picture of how chimps change their call structure, and how long the process takes. However, he'd like to see more evidence that the Dutch chimps have thoroughly learned their language lesson.
"Imagine hearing a vocalization and thinking to yourself, 'That is the sound I hear others, or I myself, make when I am eating apples.' You can test this by presenting calls to a chimpanzee and then, for example, seeing if they will go to the 'apple' tree. Thus, the sounds are functionally referential," he explained. "This is what some of the researchers had previously done. But for this study, they did not take the new apple sound produced by some of the chimpanzees and test them to see if they could identify the new sound as 'apple.'"
Taglialatela said "this seems like a key bit of data that is needed."
In addition to Slocombe and Townsend, the authors of "Vocal Learning in the Functionally Referential Food Grunts of Chimpanzees" include Stuart Watson, Anne Schel, Claudia Wilke, Emma Wallace, Leveda Cheng and Victoria West.