Birds of a feather don’t just flock together—they also work together to obtain food. Recent research makes rooks the first nonprimates observed to successfully cooperate to retrieve a food-laden platform, according to a June 22 study in the journal Proceedings of the Royal Society B: Biological Sciences.
Scientists at the University of Cambridge tested the rooks, which are Eurasian members of the crow family, by placing dishes of food on a platform out of reach of a bird enclosure. A single string looped from the enclosure to the platform and back again. Moving the platform closer required pulling on both ends of the string simultaneously, a feat that is only possible if two birds work together, each tugging on one end.
The researchers found that rook pairs spontaneously learned how to solve the problem. “We were amazed that the rooks performed so well,” says lead author Amanda Seed, now at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “It’s really hard to coordinate your actions. If you wait an extra second, you miss your chance.”
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Chimpanzees, and possibly a few other primates, are the only other species that have proved themselves capable of the same task. Rooks are extremely social birds, living in colonies of hundreds of members, and are likely to have faced evolutionary pressure to learn to cooperate, Seed says.
Further investigation, however, revealed that the rooks may not have as sophisticated an understanding of the task as apes seem to have. Previous research has shown that once a chimp learns it needs a partner to move the platform, it will no longer attempt the task if it is alone. The rooks in Seed’s lab, on the other hand, kept trying (and failing) to move the platform alone, even after successfully obtaining the food with a partner.
Seed theorizes that these results may stem from the differences between rook and chimp communities. Although rooks are social birds, they are monogamous and mate for life, making for a relatively stable adult rook society. Chimps, on the other hand, are polygamous, which makes relationships complicated, variable and difficult to negotiate. As a result, Seed says, chimps may have faced evolutionary pressure to develop a more sophisticated understanding of cooperation, competition and social relationships than rooks have.
Editor's Note: This story was originally printed with the title "Rooks Take Food"