"It's harder to see such clear examples in the wild although we strongly suspect this kind of thing is going on," said Anne Pusey, a professor of ecology, evolution and behavior at the University of Minnesota, and director of Jane Goodall Institute's Center for Primate Studies. "What's so nice about this [new research] is these stones have one purpose and they're collected in advance. This seems like a very clear-cut example."
Pusey noted other examples of apparently deliberate, forward-thinking behavior by chimps in the wild: walking long distances to food sources, such as a fruit tree or termite mount. "This gives us a strong feeling that they have in mind some future goal," she said.
The new paper caps 10 years of observation of Santino, for years the dominant and only male chimp at the zoo.
Not only did Santino collect stones from a waterbed, he also chipped away at concrete rocks in the center of the exhibit's island. He was observed knocking on the rocks, apparently until he heard a hollow sound, then striking harder blows to knock off pieces.
Zoo employees -- referred to as "informants" for the purposes of the study -- recalled removing hundreds of ammunition caches over the years. All were hidden at the shoreline facing the visitors' section. Employees said they had never found a store on the non-visitors' side of the island.
Santino was seen collecting stones at least 50 different times and making concrete discs at least 18 times. He threw 10 or more stones/discs at a time, events that one caretaker described as "hail storms."
Orvath, the study author, relied largely on interviews with zoo personnel. "For ethical and legal reasons, it has ... not been possible for the author to systematically follow stone and concrete ammunition from its gathering until its use in throwing," he wrote.
Chimp aggression generated terrifying headlines last month when a
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