CNET también está disponible en español.

Ir a español

Don't show this again

Christmas Gift Guide
Sci-Tech

Ravens recognise cheaters, give them the cold shoulder

Ravens have demonstrated a behaviour previously only observed in primates: Recognising and punishing selfish fellows.

Cooperative behaviour in ravens includes corrective behaviour previously observed only in primates. © Mario Cea Sanchez/Copyright : www.biosphoto.com/Biosphoto/Corbis

In order to keep a society running smoothly, there are basic rules of behaviour that keep members of that society cooperating comfortably. Members who violate those rules and indulge in competitive rather than cooperative behaviour will find life pretty uncomfortable. Other members of the group will ostracise deviant members in order to maintain social cohesion. In other words, if you act like a jerk? Enjoy Coventry.

This kind of social policing had previously been thought unique to primate societies, but now it seems corvids are in on the action. Ravens have been observed punishing fellow ravens who act competitively.

"From the wild, it was already known that ravens are able to cooperate when, for example, mobbing predators," explained lead author Jorg Massen of the University of Vienna in Austria. "But using an experimental set-up working with captive ravens now allowed us to investigate how exactly they do so."

Corvids, such as crows and ravens, have demonstrated intelligence levels that seem on par with non-human primates. They have proven themselves able to wield tools, and understand cause and effect in many ways. For instance, they can solve multi-step puzzles, and exercise self-control if they know there is something good in it for them. They can recognise individual humans, and have been observed holding "funerals," most likely a form of danger learning, so as to try to avoid that cause of death in the future.

Massen's experiment was designed to examine how ravens cooperate with one another.

It involved a sliding platform attached to two pieces of rope. Both ravens had to pull on their respective pieces of rope at the same time, which would bring the platform, holding two pieces of cheese, into reach. If one of the ravens let go of the rope, or if only one raven pulled, the other rope would slip down, and both ravens would miss out on the cheesy treat.

The birds figured out and completed the task with ease, but with a caveat: They did not work equally well with every other raven.

The ravens, raised in a research station, voluntarily participated in the research: they came when their names were called, in expectation of treats above and beyond their usual healthy diet. Jorg Massen

If one of the ravens cheated and took both pieces of cheese for themselves, leaving none for their buddy, they didn't get away with it. When paired with the same individual in later tests, the raven that missed out on the treat would fail the task, possibly on purpose, since they had understood it before. This would deprive the cheating raven of cheese, thereby punishing them.

Cheating ravens, on the other hand, didn't really learn their lesson. After successfully cheating once, they became more likely to cheat again. This could indicate that the food, rather than punishment, is the motivator. Once the raven who missed out on the food completed the task without receiving anything, they may be disinclined to extend themselves again for no reason, while the cheater who got extra food continues the strategy that gained it.

Massen certainly seems to think that punishment is a possibility, however. "Such a sophisticated way of keeping your partner in check has previously only been shown in humans and chimpanzees, and is a complete novelty among birds," he said.

You can find out more about corvid cooperation here, and read Massen's paper, published in the journal Scientific Reports, here.

I, for one, welcome our new avian overlords.