By Sharon Begley
NEW YORK (Reuters) - Just as Bostonians moving to Tokyo ditch "grapefruit" and adopt "pamplemousse," so chimps joining a new troop change their calls to match those of their new troop, scientists reported on Thursday in the journal Current Biology.
The discovery represents the first evidence that animals besides humans can replace the vocal sounds their native group uses for specific objects - in the chimps' case, apples - with those of their new community.
One expert on chimp vocalizations, Bill Hopkins of Yerkes National Primate Research Center in Atlanta, who was not involved in the study, questioned some of its methodology, such as how the scientists elicited and recorded the chimps' calls, but called it "interesting work."
Chimps have specific grunts, barks, hoots and other vocalizations for particular foods, for predators and for requests such as "look at me," which members of their troop understand.
Earlier studies had shown that these primates, humans' closest living relatives, can learn totally new calls in research settings through intensive training. And a 2012 study led by Yerkes' Hopkins showed that young chimps are able to pick up sounds meaning "human, pay attention to me," from their mothers.
But no previous research had shown that chimps can replace a call they had used for years with one used by another troop. Instead, primatologists had thought that sounds referring to objects in the environment were learned at a young age and essentially permanent, with any variations reflecting nuances such as how excited the animal is about, say, a banana.
In the new research, scientists studied adult chimpanzees that in 2010 had been moved from a safari park in the Netherlands to Scotland's Edinburgh Zoo, to live with nine other adults in a huge new enclosure.
It took three years, and the formation of strong social bonds among the animals, but the grunt that the seven Dutch chimps used for "apple" (a favorite food) changed from a high-pitched eow-eow-eow to the lower-pitched udh-udh-udh used by the six Scots, said co-author Simon Townsend of the University of Zurich. The change was apparent even to non-chimp-speakers (scientists).
"We showed that, through social learning, the chimps could change their vocalizations," Townsend said in an interview. That suggests human language isn't unique in using socially-learned sounds to signify objects.
Unanswered is what motivated the Dutch chimps to sound more like the Scots: to be better understood, or to fit in by adopting the reining patois?