Aesop’s fable “The Crow and the Pitcher” has been confirmed in a wonderful experiment. In the classic tale, a thirsty crow uses stones to raise the level of water in a pitcher until it rises within reach of its beak. This is no mere fiction – rooks, close relatives of crows, have the brains to actually do this.
The aptly named Chris Bird, along with Nathan Emery, gave four captive rooks (Cook, Fry, Connelly and Monroe) a chance to reach a small worm floating in a cylinder of water, with nothing but a small pile of stones sitting on the side. All of them solved the task, and Cook and Fry succeeded on their first attempt. They were savvy about the stones too, using exactly the right number to bring the water within reach and preferring larger stones over smaller ones.
The accomplishments of Bird’s rooks are even more impressive when you consider that rooks are not natural tool-users. Many of the corvids – crows, ravens and the like – are avid tool-users and the skills of the New Caledonian crow are rapidly becoming the stuff of popular science legend. But rooks are different – even though they too excel in laboratory tests (as Bird and Emery have previously shown), they hardly ever use tools in the wild. Rather than any special tool-using adaptations, their skills must stem from the sort of general intelligence that great apes are thought to possess.
More so than other members of the family, rooks are extremely opportunistic feeders, relying on a varied menu of seeds, insects, dead meat and rubbish. With such catholic tastes, food is never far from their beaks and they may have little need for specialised tricks involving tools. The same might be true for capuchin monkeys, which happily brandish tools in a lab but only ever use them in the wild when food is scarce. As Aesop’s fable moralised, “Necessity is the mother of invention.”
In 1997, Swedish inspectors found several stockpiles of missiles hidden in a local zoo. Apparently, the arsenal had been gathered together for the express purpose of being used against civilians. And who was the mastermind behind this collection? A 19-year-old chimpanzee called Santino.
Santino was born in a German zoo in 1978 and transferred to Furuvik Zoo at the age of 5. To this day, he lives in the zoo’s chimpanzee island – a large outdoor enclosure surrounded by a moat. Throughout his residence, he was mostly docile towards the eager visitors, but all of that changed in 1997 when he started chucking disc-shaped stones at them.
Now many of us may have secretly wanted to take part in a spot of tourist-stoning, but Santino’s antics became so common that visitors were actually in real danger. The zoo staff had to take action. One morning, they swept the chimpanzee island and (unlike some other weapons inspectors) they actually found Santino’s arsenal – five separate caches of stones dotted along the shoreline facing the public area. Each one contained 3-8 missiles including concrete slabs, and algae-covered stones that had clearly been taken from the moat.
Mathias Osvath from Lund University, who describes the behaviour in a new paper, believes that it’s clearly premeditated. Until now, it’s been very difficult to work out if natural chimp behaviour involves true forward-planning or represents a reaction to present circumstances. Is a chimp that gathers twigs for termite-fishing planning for the future, or just responding to a more immediate hunger?
There’s no easy answer to that, but Santino’s case is much clearer. One of his caretakers, Ing-Marie Persson has collected plenty of evidence to show that he was deliberately stockpiling weapons of individual destruction for future acts of tourist-stoning.