From November 11, 2006
In my last few posts you may have noticed a theme: signals that are used to advertise sex in the animal world are generally thought to be honest ones. In fact, animal communication in general is pretty truthful. There may be different reasons for this: some signals may be impossible to fake (for instance, toad calls may contain honest information about the caller’s size simply because bigger bodies produce lower-frequency sounds). But even when a signal could be faked, the evolution of dishonest signaling is very unlikely. There is a simple reason for this: in the long run it would not benefit receivers to respond to a signal that could be cheated.
This is something that we might find surprising given the amount of deception that goes on in human interactions. Is deception really so rare in animal communication systems? Are there any animals liars?
We have some examples of deceptive communication between different species: for example, ground-nesting birds will fake an injury to draw a predator away from their nest, and some birds in mixed-species flocks will give false alarm calls to increase their own foraging success. Within species, however, the examples of deception are few. We know deceptive communication occurs within a number of primate species. Interestingly, some recent work using ravens has shown that, much like many primates, birds may also be capable of intentionally deceiving conspecifics.
This result came as a bit of an accident during an experimental study on social learning and scrounging in foraging ravens. The researchers provided their ravens with a series of covered plastic boxes that served as food caches (some containing pieces of cheese; some empty). The boxes were arranged in clusters and ravens were videotaped during their foraging explorations. Right from the start, the researchers noticed an interesting pattern between a pair of male ravens: rather than search for his own food, a dominant male relied on a subordinate male’s explorations, following the subordinate male around and eating the food that he discovered.
It eventually became apparent to the researchers that the subordinate raven wasn’t the only one being exploited in this situation. He had developed a strategy to trick his competitor. Whenever the subordinate male found a cluster of boxes containing food, he would quickly move on to a different cluster and start opening boxes there. The dominant male would soon follow, leaving the subordinate free to return to the other boxes and enjoy his snacks at leisure.
The parallels here to primate behaviour are interesting: chimpanzees have been known to walk away from a food site in order to induce other group members to do the same, and then return later to enjoy the food in privacy. Does the ability to communicate deceptively say something special about the cognitive evolution of a species?
You can read the raven study here.