Wednesday, September 23, 2009
Bird brains get even more clever.
New Caledonian crows, already known for clever tool-making in the wild and in the lab, are now shown to be able of using three tools in the correct order to bag a treat. Such sequential tool use has never been observed in any other untrained nonhuman animal. In the wild, the crows (Corvus moneduloides) regularly fashion barbs and hooks from leaves and twigs to extract grubs from holes and crevices. In the new experiments, each of seven crows was given a test tube stuffed with a tasty piece of meat that could be pried out only with a particular stick. To get at the meat, the birds had to do three things in the right order: pick up a short stick, available on the cage floor, and use it to pull a longer stick out of a second test tube; use that stick to extract an even longer stick from a third test tube; and then use this longest stick to get the prize. Four crows were successful. It seems unlikely that they were selecting sticks at random, because they usually swapped sticks for longer ones.