Natural born tool-makers: the crafty crows from New Caledonia
A captive-bred immature New Caledonian crow that was raised by human foster parents in the Oxford lab (photo: Ron Toft). This crow used and even manufactured tools, although it had never been allowed to observe other crows or humans handling tool-like objects.
Mr Lucas Bluff, Professor Alex Kacelnik, Dr Christian Rutz, Dr Alex Weir and Ms Joanna Wimpenny
University of Oxford
Humans are without doubt the masters of making tools. Other creatures demonstrate basic skills, for example chimpanzees use sticks to dig out termites and stones to break open nuts, but apart from humans the most specialised tool-maker is Corvus moneduloides the New Caledonian crow. 'No other animal exerts fine or precise control over the shape of their tools, in the way these crows do,' says Alex Weir of the Department of Zoology at the University of Oxford.
New Caledonian crows are, as their name suggests, native to the island of New Caledonia in the South Pacific. More than 20 of them live in aviaries at the University of Oxford. The most famous is Betty who, in carefully designed experiments, has shown an understanding of what is called 'folk physics'. Alex explains, 'Humans use folk physics to understand the way objects interact. We know an object will fall to the ground if dropped even if we don't understand gravity'. An experiment was used to test whether two crows, Betty and Abel, would spontaneously choose the right tool for a particular task. The experiment didn't exactly go to plan but still provided some startling results.
A bucket of meat was placed inside a tube and two pieces of wire supplied: one hooked, one straight. After some failed attempts to use the hooked wire to retrieve the bucket, Abel flew off with it, leaving Betty with the straight wire. To the researchers' surprise, she bent it into a hook and got to the meat. Betty went on to make hooks from wire consistently in further experiments confirming that this wasn't just a fluke.
'The crows were unlikely to have come across wire in the wild and had never used it or seen it being used in captivity', says Alex. The experiment therefore represented spontaneous, novel tool making and problem solving something which has not been demonstrated in any other non-human. Betty has gone on to make hooks out of a different material (aluminium strips), and shown that she can unbend a hook when a longer tool is needed.
But are the birds' skills limited to making tools? 'It could be that the crows' mental abilities are specialised for tool making,' says Alex, 'or they could have generally good mental skills that they apply to making tools'. Experiments currently under way suggest that the crows are able to apply their skills flexibly to many tasks involving tools, and perhaps to some that do not.
The work with crows may throw light on the evolution of the human brain. Human brains differ greatly from the brains of great apes making it hard to relate structural differences to abilities. In species of crows, the brains are quite similar. Comparing the brains of the New Caledonian tool-makers with non tool-making crows may enable identification of parts of the brain involved in making tools. 'Although human and bird brains do differ substantially, many areas have the same evolutionary origins, and perform similar functions, so we may be able to learn something about the evolution of human brains,' says Alex.