Monkeys Have Accents, Japanese Study Finds
for National Geographic News
|December 28, 2005|
New Yorkers have them. So do Georgians, Texans, Brits, and Australians.
Now primate researchers have discovered that Japanese macaques can acquire different accents based on where they livejust like humans.
The red-faced monkeys frequently utter what researchers have dubbed coo calls to maintain vocal contact with one another.
Recordings of these calls taken over an eight-year period show that macaques living hundreds of miles apart "speak" at different frequencies.
The finding, the first of its kind, will appear in the January 2006 edition of the German scientific journal Ethology.
"One of the characteristics of human language lies in its modifiability," said Nobuo Masataka, a professor of animal behavior at Kyoto University's Primate Research Institute, in an email to National Geographic News.
"Japanese monkey vocalizations share this characteristic with our language."
Researchers at the institute recorded the coo calls of two groups of macaques (Macaca fuscata), also called snow monkeys, that used to be part of the same population but have lived apart since 1956.
The first group consisted of 23 inhabitants of the southern Japanese island of Yakushima. The other group of 30 monkeys lives on Mount Ohira in central Japan.
The two groups are more than 434 miles (700 kilometers) apart and have had no contact with each other since their separation, researchers say.
Vocal recordings from both groups were taken intermittently between 1990 and 1998.
The scientists focused on female macaques because they are the main coo callers. The monkeys usually produce these sounds in relaxed situations, such as when feeding, grooming, or resting.
Since it's possible that calls vary acoustically during different types of behavior, researchers only analyzed vocalizations produced by the monkeys when feeding.
The result showed that the Yakushima monkeys had a tone about 110 hertz higher, on average, than the Mount Ohira group.
The difference is probably linked to the monkeys' habitats. The island group lives in an evergreen forest with high trees that tend to block sound. The Ohira monkeys reside in an open, gravelly range with little vegetation.
"Higher sound is likely to transmit more effectively in the forest than lower sound," Masataka explained.
Until now, monkeys and apes were thought to be poor vocal imitators, said Frans de Waal, director of the Living Links Center at Emory University in Atlanta, Georgia.
Humans were considered to be the only primates able to mimic each other's vocalizations, such as when learning how to pronounce new words.
"This exciting new study suggests that monkeys from the same genetic stock may, in a couple of decades, develop different call features," de Waal said.
"It shows greater vocal flexibility than assumed for primates beforeperhaps even cultural variation, such as in human dialects."
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