A while ago, I noted this development:

No fewer than 22 times, researchers documented wild chimpanzees on an African savanna fashioning sticks into ‘spears’ to hunt small primates… In each case a chimpanzee modified a branch by breaking off one or two ends and, frequently, using its teeth to sharpen the stick. The ape then jabbed the spear into hollows in tree trunks where bush babies sleep… Anthropologist and study co-author Paco Bertolani witnessed… a chimpanzee successfully extract a bush baby with a spear.

Now, via Dr Westerhaus, comes more news from the animal kingdom:

A male chimpanzee in a Swedish zoo planned hundreds of stone-throwing attacks on zoo visitors, according to researchers. Keepers at Furuvik Zoo found that the chimp collected and stored stones that he would later use as missiles. Further, the chimp learned to recognise how and when parts of his concrete enclosure could be pulled apart to fashion further projectiles.

The findings are reported in the journal Current Biology. There has been scant evidence in previous research that animals can plan for future events. Crucial to the current study is the fact that Santino, a chimpanzee at the zoo in the city north of Stockholm, collected the stones in a calm state, prior to the zoo opening in the morning. The launching of the stones occurred hours later – during dominance displays to zoo visitors – with Santino in an “agitated” state. This suggests that Santino was anticipating a future mental state – an ability that has been difficult to definitively prove in animals.

I know. If they learn to make fire, we’re screwed.