We tend to think that planning ahead is a purely human activity, but the antics of a chimp called Santino in Furuvik Zoo in Sweden are challenging that assumption.
Three years ago Santino hit the headlines when researchers found that he was gathering stones into piles before the zoo opened in the morning, ready to pelt visitors. Not only is this rather cheeky, but it looked like he was actively planning ahead for the day's assaults. Some scientists argued that Santino wasn't actually planning ahead, but instead was just repeating what he had learned to do, as a result of his time in the zoo.
But now new observations from Mathias Osvath and Elin Karvonen, published in the journal PLoS One this week, suggest that Santino is indeed a forward-planning, as well as a cheeky, monkey - or rather, chimp (before any pedants complain).
The researchers watched groups of visitors to Santino's enclosure, and saw him threatening them with stones. Understandably, they backed off, but when they went closer again, Santino was holding stones but just playing it cool, doing his chimp thing. But then he suddenly threw a stone at the visitor group, as if he had been planning to trick them.
Osvath and Karvonen also saw Santino hide stones under handfuls of hay or behind logs in prime spots for throwing, so visitors wouldn't spot the missiles as they approached - suggesting that he knew visitors would come and was planning to attack them.
The scientists argue that Santino didn't hide stones like this before 2010, and that it shows that he is forward-planning.
Sceptics still aren't entirely convinced, however, arguing that it's hard to interpret his behaviour to this degree, that he might be hiding the stones for another reason, and that he's just one chimp that may not be representative of the rest of the species.
So while these observations hint at the fact that at least one chimp out there may be planning for the future, there's a lot more work to be done to figure out whether chimps - or any other animals - can actively plan ahead. Though even if they can, they're unlikely to be buying into a pension plan any time soon.