Humans don’t learn everything from every generation, and neither do crows, it seems.
Cultures accumulate knowledge cumulatively over time by drawing on the know-how of those who came before them. It requires a complex cognitive ability capable of memory, language, imitation, teaching, and imagination.
It turns out that New Caledonian crows also have sophisticated brains, although no tradition of language, teaching, or imitation to our knowledge. They can remember what they have seen and even design tools based on memory, without having seen the tool built. It is a rare skill in the animal kingdom. In a study in Scientific reports published today (June 28), researchers at the University of Cambridge in England and the University of Auckland in New Zealand argue that ‘mental pattern matching’ enables crow culture to pass on traditions tool manufacturing.
New Caledonian crows make basic stick tools, hook stick tools, and barbed tools from plant leaves. It is not clear if they learn tool designs from each other or how those designs have apparently improved over time. In the wild, crows do not seem to closely observe or imitate each other. Yet particular designs have been observed in different fields over the course of several decades, and during this time the tools have improved. This suggests, according to the study, that tool-making skills are moving across populations of crows, although how the knowledge is transmitted remains a mystery.
Researchers believe that crows create a mental model of tools – like humans, they can see something and, without monitoring the manufacturing process, shape a similar or better item.
To test this theory, the team asked eight crows to craft tools from unknown materials and collect food from a vending machine with the tools. They explain in the study:
We developed an arbitrary crafting task that mirrored pandanus tool crafting, in that it required tearing material in order to gain food. However, instead of pandan leaves, we used an unknown crafting material (card). By forcing the crows to use this man-made material to create objects that take different shapes from pandanus tools, our task had enough novelty to prevent the crows from transferring the learned rules formed during their earlier experience of making tools into nature.
Six of the eight crows in the study were successful in fashioning tools from the paper cards, although the material lacked the qualities that the leaves have, such as veins, which makes the task more difficult. The two who failed were young people, indicating that their cognitive abilities were not fully developed.
A particularly intelligent crow named Emma was super skilled. Emma made changes to the tools on the map so that they look more like the tools she first saw and are more consistent all around.
“Our results provide the first evidence suggesting that New Caledonian crows have the cognitive ability to make objects from a mental model,” the study said. Based on their findings, researchers now believe that crow culture evolves with memory. âThe matching of mental models is now the main hypothesis to explain why the crow tools of New Caledonia present some of the characteristics of cumulative cultural evolutionâ, they conclude.