Thai monkeys have been observed showing their young how to floss -- proof primates teach offspring to use tools, a Japanese researcher said Wednesday.

"I was surprised because on properly to a third party are said to be an activity carried out only by humans," Professor Nobuo Masataka of Kyoto University's Primate Research Institute told AFP.

His research team observed seven female long-tailed and their and monitored how often the mothers cleaned the spaces between their with strands of human hair, in a colony of 250 animals near Bangkok.

The study found that the frequency of teeth-cleaning roughly doubled and became more elaborate when the infant were watching, suggesting that the females were deliberately teaching their young how to floss, he said.

"The study is still at the hypothesis stage," Masataka cautioned. "We would like to shift our focus to the baby monkeys to check whether the mothers' actions are effectively helping them learn how to clean their teeth."

(c) 2009 AFP