STOCKHOLM – A canny chimpanzee who calmly collected a stash of rocks and then hurled them at zoo visitors in fits of rage has confirmed that apes can plan ahead just like humans, a Swedish study said Monday. Santino the chimpanzee's anti-social behavior stunned both visitors and keepers at the Furuvik Zoo but fascinated researchers because it was so carefully prepared.

According to a report in the journal Current Biology, the 31-year-old alpha male started building his weapons cache in the morning before the zoo opened, collecting rocks and knocking out disks from concrete boulders inside his enclosure. He waited until around midday before he unleashed a "hailstorm" of rocks against visitors, the study said.
Osvath said the chimpanzee had also been observed tapping on concrete boulders in the park to identify weak parts and then knocking out a piece. If it was too big for throwing, he broke it into smaller pieces, before adding them to his arsenal.

"It is very special that he first realizes that he can make these and then plans on how to use them," Osvath said. "This is more complex than what has been showed before."
Story: http://news.yahoo.com/s/ap/20090309/...en_angry_chimp

This is pretty awesome.