Monkeys That Floss With Human Hair Learn From Mom?

Charles Q. Choi
for National Geographic News
March 12, 2009
Long-tailed macaque monkeys teach their babies to clean their teeth, according to a new study that says females slow down and exaggerate their motions when they notice their young watching them floss.

Macaques living near a Buddhist shrine in Lopburi, Thailand, are known to pull out hair from visitors to use as floss.

Worshipers see the monkeys as divine servants, the researchers said, which helps explain why people let the macaques pull out their hair.

About 50 of these monkeys have been seen jerking strands of hair back and forth between their teeth. Similar behavior has been seen before using coconut fibers or twigs.

To find out how the macaques learn to floss, primatologist Nobuo Masataka at Kyoto University and his colleagues scattered 8-inch-long (20-centimeter-long) hairs from a wig throughout the shrine and videotaped the primates in action.

The researchers focused on seven female adult macaques, each with a one-year-old infant.

When the mothers sat face-to-face with their young, each bout of flossing took roughly twice as long as usual, and the mothers paused and repeated themselves about twice as often.

Markedly similar exaggeration of actions occurs in humans between mothers and children, Masataka said. Scientists have dubbed this teaching behavior motionese.

"These findings suggest education is a very ancient trait in the primate lineage," Masataka said. The last time humans shared an ancestor with macaques, according to genetic analysis, was roughly 25 million years ago.

Further research is needed to confirm if and when the infant monkeys are actually learning to floss from these lessons, Masataka noted.

Findings detailed in the journal PLoS ONE.

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