This New Caledonian crow has a foraging tool firmly in its beak. The more helpful it is, the better the bird will take care of it.
The crows use various tools to get prey from tree hollows or other hiding places. If they want to eat the food they have captured, they have to put the tool out of their beak – and risk it being lost or stolen by a member of their own species. It has long been known that birds take protective measures for this: They clamp the tool under their feet or hide it in a nearby hole or behind bark.
Researchers at the Max Planck Institute for Animal Behavior in Konstanz and the University of St. Andrews in Scotland examined this behavior more closely in a study. You could divide the tools used by the crows into two groups, hooked and hookless. The tools with hooks are painstakingly made from a rare type of plant, while the others consist of simple twigs or leaf litter. “Tools with hooks are not only more expensive to purchase, but also much more efficient,” explains team leader Christian Rutz. “Depending on the task, crows can prey up to ten times faster with these tools than with conventional tools without hooks”.
Scientists observed that crows are more likely to keep efficient tools safe than simple ones. “This suggests that they have some idea of the relative ‘value’ of the different tool types,” said study co-author James St Clair. This study is the first to draw conclusions from the way animals use their tools about how much they value these items. The innovative method has great potential for studying the behavior of other animal species that use tools – including our closest relatives, the chimpanzees.