Researchers have found that ravens – which in Norse mythology acted as Odin’s eyes and ears on Earth and brought information to the god – appear to known when other birds, that might steal their food, are watching them.
In the new study – published Tuesday (Feb. 2) in the online journal Nature Communications – the researchers looked at the behaviour of ravens to figure out whether they could interpret other bird’s thieving intentions.
Thomas Bugnyar, lead author of the study and a cognitive biologist at the University of Vienna, said that ravens have quite complex interactions with each other and are highly social birds.
Even foraging can be a social activity for raves, according to Bugnyar. They get help from other ravens to gain access to food, he said. Ravens also tend to set food aside for later, in a hidden place, instead of eating until they’re full – which is called “caching.” The birds then repeat the same thing until the entire food is gone.
Bugnyar and his colleagues found that in order to steal food with utmost efficiency, the ravens watched the other birds as they visited their caches to store food over and over again. Since ravens have very good observational memories, they remembered not only the caches they made themselves, but also the ones made by the other birds.
For the new study, the researchers placed two ravens into two chambers (one in each) connected by a wall with windows. The raven in the first chamber was given food, while the other watchful rival was placed in the second chamber.
At first, the windows were left uncovered. The researchers found that the raven in the first chamber guarded its cache of food carefully. When they covered the window, the first raven did not guard its food as closely, even though it was aware of a potential thief nearby.
In a third experiment, the researches opened a peephole, but left the rest of the window covered. The second raven was removed from its chamber; however the researchers played recorded raven calls as if the rival bird was still hiding in the second chamber.
They found that the first raven did not return to its cache that often (because it did not want to give away its hidden location), and also ate its food more quickly than when the peephole was closed. In both the first and third experiment, the raven placed its cache where it would be less visible to the rival bird.
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