A chimp that stockpiles weapons

A chimpanzee that lives in a Swedish zoo has a habit of stockpiling stones and other small objects that he can throw at visitors when a crowd begins to form. It's an unusual instance of an animal planning ahead for a future contingency:

"Many animals plan. But this is planning for a future psychological state. That is what is so advanced," said Mathias Osvath, director of the primate research station at Lund University and author of the paper in the journal Current Biology.

The animal's preparations include not only stockpiling the stones he finds, but more recently also fashioning projectiles from pieces of cement he has broken off artificial rocks in his habitat.

Others have observed great apes planning, both in the wild and in captivity. Some birds in the corvid family that includes jays and ravens also plan for future contingencies. In general, though, planning by animals is thought to occur only when the payoff is immediate and more or less certain.

"People always assume that animals live in the present. This seems to indicate that they don't live entirely in the present," said Frans de Waal, a primatologist at Emory University in Atlanta, who was not involved in the research.