When male chickens come across food, they make a 鈥渢ook, took, took鈥� call to tell the flock 鈥� but hens react only if they don鈥檛 already know that food is around.
This shows that the call triggers other chickens to look for specific information 鈥� in this case, whether or not they already know there is food about 鈥� and to respond appropriately, researchers claim. This is similar to how human language works, they say.
Such 鈥渞epresentational鈥� communication has been demonstrated in some primates before, but never in a bird.
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Critics of the idea that certain animal calls might have similarities with language have suggested, for instance, that the calls might simply be triggering a reflex response, or that researchers might be over-interpreting a call鈥檚 meaning.
鈥淚n this work, we have shown that the hens鈥� response is mediated by a representation of food,鈥� says Chris Evans. He and Linda Evans, both animal behaviourists, studied a type of domestic chicken, called golden Sebrights (Gallus gallus), at Macquarie University in Sydney, Australia.
Language-like qualities
Several animal species produce sounds that trigger a particular response among other members of their group. These calls are usually related to the presence of either a predator or food. For example, meerkats produce several different types of alarm call.
It takes careful experimentation to show that calls really stand for something specific in the environment, and so have language-like qualities, however. So far, this has been shown only for a few mammals, in particular Diana and Campbell鈥檚 monkeys.
Evans and Evans played back the golden Sebright food calls to hens, either directly after giving them a few corn kernels to eat or after giving them nothing. The calls only triggered the hens to start peering at the ground to look for food if they had not just received corn.
鈥淚f you鈥檙e on a long drive and you pass a restaurant sign, that could be a salient piece of information. But if, after food has been brought to the table, someone says: 聭There鈥檚 food,鈥� that鈥檚 a redundant comment. It鈥檚 that kind of contrast,鈥� Chris Evans explains.
More work is needed to understand why language-like calls arise in some species but not others, he says, though it does seem that they occur in animals that live in stable social groups surrounded by kin.
Journal reference: Biology Letters, DOI: 10.1098/rsbl.2006.0561)
