By Richard Collins

In The Descent of Man, Darwin claimed chimpanzees use tools. Nobody believed him at the time. Long after his death, however, great apes were filmed using stones to break open the hard shells of nuts. Other primates displayed similar skills. Then dolphins and elephants were admitted to the exclusive tool-using club, while fish were observed smashing shells on stones. Octopuses perform remarkable intellectual feats.

Although parrots and Egyptian vultures routinely use tools, our feathered friends were deemed too ‘bird-brained’ to be intellectuals. Having to be as light as possible for flight, carrying big brains around simply wasn’t an option. Then, in 2002, a crow named Betty confounded everyone with the tool-using skills she displayed in an Oxford laboratory.

New Caledonian crow (Corvus moneduloides), using a ‘tool’ to dislodge a worm.

Betty hailed from New Caledonia, an island in the South Pacific. The crows there feed on grubs which live deep in rotting wood. Birds will poke twigs into holes in the wood to prise out the prey.

When researchers placed food out of her reach in the laboratory, Betty picked up a piece of wire and raked it in. Other crows did the same, but Betty went further. Presented with food in a little bucket placed inside a container, she picked up a straight piece of wire but failed to retrieve it. Having reflected on the problem, she inserted the wire into a hole and bent the tip into a hook. She then looped the handle of the bucket and dragged it out of the container.

This was thought, at the time, to be a feat of which only humans were capable. Betty seemed to have conceptualised the problem, modelled the situation in her head and devised the successful strategy. Was she, therefore, capable of abstract thought?

Researchers from the University of St. Andrews argued that she wasn’t. Working in New Caledonia, they noticed that the crows there preferred to use curved, rather than straight, twigs as tools and some birds routinely bent straight twigs before using them. Betty’s behaviour, they suggested, was neither original nor genuinely creative. It was just part of her inherited instinctive repertoire.

Now the controversy has erupted again. Scientists from Oxford and Germany’s Max Planck Institute for Ornithology have published a paper in Scientific Reports, in which they claim that captive New Caledonian crows not only construct tools, but are able to solve problems they never encountered previously.

In one experiment, eight crows were presented with a box which had food placed deep inside it. All eight of the birds inserted tools through a gap in the side of the box and pushed the food towards a door where they could reach it; so far so good. Then the birds were presented with pieces of tool too short to reach the food. Four individuals solved that problem. They fitted the pieces together to form a tool long enough for the job. The number of pieces used was ‘conditional on the position of food’, say the authors; one crow assembled three or four piece tools as required. Only the great apes are thought to be capable of such a feat and children must be several years old before they can manage it.

The authors claim that ‘these crows possess highly flexible abilities that allow them to solve novel problems rapidly’. They have ‘an ability to innovate perhaps through virtual cognitive simulations. The underlying cognitive processes however remain opaque for now’.

A. M. P. van Bayern et al. Compound tool construction by New Caledonian crows. Scientific Reports. 2018.