New York Times:
Frans B. M. de Waal, a professor at the Yerkes National Primate Research Center and Emory University, said chimpanzees or orangutans in captivity sometimes tried to lure human strangers over to their enclosure by holding out a piece of straw while putting on their friendliest face.
“People think, Oh, he likes me, and they approach,” Dr. de Waal said. “And before you know it, the ape has grabbed their ankle and is closing in for the bite. It’s a very dangerous situation.”
Apes wouldn’t try this on their own kind. “They know each other too well to get away with it,” Dr. de Waal said. “Holding out a straw with a sweet face is such a cheap trick, only a naïve human would fall for it.”
(Another remarkable chimp face photo by Flickr user ucumari.)