Video: Rooks Use Rocks to Reach Reward

Does the ingenuity of corvids—crows, ravens, and their relatives—have any limits? Just this week came the news that New Caledonian crows can use three different tools in a row to get a complex task done. Now we learn that the Rook, a European corvid, is savvy enough to displace water using stones.

If that sounds familiar, you may be remembering one of Aesop’s fables, in which a thirsty crow spies some water at the bottom of a long-necked jar. It can’t reach the water to take a drink, but it realizes that by dropping in enough stones it can raise the water level. Satisfaction!

It’s possible Aesop was inspired by seeing a crow or rook do this more than 2,500 years ago. But scientists haven’t seen this kind of problem solving in any animals other than the orangutan – until now. Comparative psychologists from the University of Cambridge and Queen Mary University of London gave a pitcher of water and some stones to four captive Rooks. A worm floated on the water but was too far down the jar for the birds to reach it.

Watch what happens in this great video. A Rook named Connelly bends down and eyes the pitcher’s water level, then starts piling stones into the jar. It takes seven stones in a row, and you can see Connelly periodically looking at his progress. Later experiments showed the birds could judge roughly how many stones would do the trick, they chose to use larger stones over smaller stones, and they realized sawdust would not work in the same way. The work appears today in the journal Current Biology.

See Rooks solve more problems on the Cell Press YouTube channel.

The Rooks in these experiments were captives, and the scientists point out that wild Rooks have never been seen using tools, but they attribute that to a lack of necessity rather than a lack of ingenuity.