Biologists at the University of St Andrews have observed tool-manufacture behaviour in wild New Caledonian crows, which may mean that textbooks on animal intelligence will have to be rewritten, according to a paper published today (Wednesday 10 August 2016) in Royal Society Open Science.
In 2002, Betty, the New Caledonian crow astonished the world, when she deftly bent a straight piece of garden wire into a neat hook to lift a small food-baited bucket from a vertical tube – a puzzle researchers had set for her in a laboratory at Oxford University. Although it was known at the time that these tropical corvids manufacture tools from twigs in the wild, it seemed highly unlikely that this involved any bending actions. Betty apparently understood the requirements of the experimental task and spontaneously came up with a ‘clever’ solution.
The paper that described these observations shook the field of comparative cognition, and is widely regarded as one of the most compelling demonstrations of ‘insightful’ or ‘intelligent’ behaviour in a non-human animal.
In an unexpected twist, however, recent field experiments by a team of St Andrews biologists have now revealed that tool bending is part of New Caledonian crows’ natural behavioural repertoire, casting doubt on Betty’s problem-solving prowess. Project leader Dr Christian Rutz explains: “We had provided wild-caught crows with juicy treats hidden in wooden logs, as well as with their preferred plant material for tool manufacture. We were absolutely over the moon when the birds started making and using tools in our field aviaries.”
But then something completely unexpected happened: some of the crows vigorously bent their twig tools during processing, in exactly the same manner as Betty had bent wire in the famous Oxford experiment – even though this time, bent tools were not required to solve the task. “We couldn’t believe our eyes,” Dr Rutz recounts. “Most birds trapped sticks underfoot before bending the tool shaft by bill, but one also pushed tools against the logs to flex them, and another wedged them upright into holes before pulling the shaft sideways, just as Betty had done. It turns out, the twigs that wild crows select for making their tools are pliable!”
Co-author Dr James St Clair notes: “Our observations raise the question of why wild crows would bend their stick tools as a matter of course. We believe a curved tool is advantageous, because the bird can position it in its bill so that the tool-tip is bang in the middle of the field of binocular vision. This should improve tool control during foraging.”
Does this discovery mean that Betty’s wire bending was not ‘clever’?
The latest observations suggest that Betty may have simply followed familiar tool processing routines, rather than inventing a clever solution to a novel problem. But they do not necessarily rule out the possibility that she ‘understood’ the task and expressed flexible, innovative behaviour.
Dr St Clair cautions: “New Caledonian crows are gifted tool users. The highly dexterous behaviour we observe in adult birds is the outcome of complex interactions between genetic predispositions and lifelong individual and social learning – a process that we don’t yet fully understand. In light of our new results, more experiments are needed to figure out what exactly these birds are capable of.”
“Our study is a powerful reminder of the importance of basic natural history research,” notes Dr Rutz: “When my Oxford colleagues studied Betty’s cognitive abilities almost 15 years ago very little was known about how these birds make and use tools in their natural tropical habitat. Our discovery of tool bending in wild New Caledonian crows has come as a complete surprise, and was the result of patient field research.”
