MONDAY, March 9, 2009 (HealthDay News) -- For years, Santino, a male chimp at the Furuvik Zoo in Lund, Sweden, was in the habit of spending two hours before the zoo opened collecting rocks and other "ammunition" to hurl at the human gawkers who started gathering outside his enclosure around mid-morning.
He stored the items at various sites around the chimpanzee island, where zookeepers were unlikely to find them and where they could be easily extracted when he was ready to "display."
This deliberate collecting, storing, then launching of rock and concrete missiles may be among the first clear evidence that an animal that is not human can engage in planning, says the author of a paper published in the March 9 issue of Current Biology.
The explanation is made all the more compelling by the fact that the chimp was in an entirely different state of mind during the planning phase of his endeavor (calm) than during the implementation phase (agitated), said the study author, Mathias Orvath, of Lund University.
"These observations fit nicely with all sorts of things apes do. I have seen apes line up feces as future ammunition," said Frans B.M. de Waal, C.H. Candler Professor of Psychology and director of the Living Links Center at the Yerkes Primate Center at Emory University in Atlanta. "This ape must have learned that during displays he would run out of things to throw and, from this, he must have extrapolated that it would be good to have a pile of projectiles at the ready."
"Apes in captivity enjoy pelting visitors and the excited shrieks and laughs they get as a reaction, which they do on a daily basis," de Waal added.
De Waal described one ape that gathered straw from inside a heated building, then took it outside for a warm nest during cold weather. This behavior only occurred in colder seasons.
"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 Stamford, Conn., woman was mauled by a 200-pound chimpanzee that belonged to her friend.
Charla Nash, 55, remains sedated at the Cleveland Clinic. During the attack, she lost her nose, lips, eyelids, hands and bone structure in the middle of her face. She also suffered severe brain, eye and tissue injuries, the Stamford Advocate newspaper reported.
ABC News said doctors don't yet know if Nash would be a candidate for face transplant surgery, a procedure recently performed for the first time in the United States at the Cleveland Clinic.
To learn more about chimp behavior, visit the Jane Goodall Institute.