A crow rips up a bit of paper to use it in a specially designed crow vending machine, showing they can remember the size of a tool that will meet their needs and match it. Sarah Jelbert.

New Caledonian crows make tools with a sophistication that arguably surpasses any animal besides ourselves. There are signs crows can learn from each other, and their technology may even be advancing, but researchers have been puzzled how such unsociable animals, lacking in language, can do this. A new study shows that even though Corvus moneduloides are relatively solitary creatures, they are capable of learning new tool-making techniques and applying them from memory in a way never before seen in animals besides ourselves and our ancestors.

Although corvids in general are impressively intelligent birds, New Caledonian crows are something special. They bend twigs and tear leaves to make hooked tools to extract grubs in the wild, and have taken to shaping wire with enthusiasm. If this still doesn't impress you much take a look at this video and ask yourself how many humans could solve a sequential challenge so quickly.

Scientists are puzzled how they acquire some of these skills, since they don't appear to imitate each other, even in captivity. Dr Sarah Jelbert of the University of Auckland has proven that when shown a novel tool, and taught its effectiveness, these crows can learn to fashion something similar from memory. She proposes in Scientific Reports crows learn from watching their parents or by finding tools discarded by others, and sometimes make advances on these, leading to a developing technological sophistication.

Jelbert taught eight crows a trick they would definitely not have evolved in the wild. She created a crow vending machine, which rewarded them with food when they inserted pieces of colored paper (portraits of reigning monarchs or notable persons not required).

Once the crows had grasped the paper-for-food idea, Jelbert gave the crows an impractically large piece of colored paper. The crows tore the paper up, four of them without needing a hint, until sections could fit into the machine. The birds were then presented with sheets of two different colors, and only rewarded when they made currency out of one of them. All but one bird quickly learned to only use the right colored paper.