SputnikPanic writes: According to a Washington Post article, a scientific paper being published today describes a chimpanzee that demonstrates a rather interesting capacity: the forethought to stockpile stones to be used as weapons. The chimp, which is at a zoo in Sweden, collects rocks prior to the zoo's opening so that he may have them ready for use later in the day when he becomes agitated by visitors. "Many animals plan. But this is planning for a future psychological state. That is what is so advanced," says Mathias Osvath, a researcher and author of the paper. In another example of sophisticated behavior, "About a year after his storing and throwing began
... the animal began tapping stones against the concrete artificial rocks, listening for a hollow sound that indicates a fissure. He would then hit the concrete harder until a piece chipped off, occasionally then hitting it again to make it fist-sized."