Australian scientists have found that chickens possess communicating calls far more sophisticated than previously thought.

Communication is found throughout the animal kingdom, but researchers usually translate them as sexual, territorial or emotional (revealing fear, anger, etc).

But "representational signaling" (e.g. for food or predator) was thought to be unique to human, and eventually to some highly evolved mammals.

The researchers investigated food calls to adult golden Sebright bantam hens, which possess calls very similar to those of the red jungle fowl ( Gallus gallus), the ancestor of the domestic hen.

For their surprise, they found that rather than simply expressing food finding joy, the high-pitched "tck, tck" calls the birds made actually meant "here is some food": this is representational signaling.

"Hens responding to food calls do so because these sounds encode information specifically about food," said Dr Chris Evans.

Observing 17 birds, the researchers noticed that fellow hens foraging around constantly emit calls, but the calls' frequency changes when finding food, producing them at a higher rate if a highly preferred food item is encountered.

"For example, corn evokes calls that are clearly distinct from those given to their regular ration," Dr Evans said.

Till now, foraging signaling calls have been observed only in primates; these are the first observations of this behavior in non-primate animals.

"There is hence a strong parallel between the cognitive mechanism engaged by representational signals and the denotative function of words."

Sophisticated communication like representational signaling seems to be the result of social life "rather than an attribute of our own evolutionary lineage", said Evans.

"To the extent that our attitudes toward animals are shaped by their perceived mental life, such findings should be thought-provoking," Chris Evans told.

Scientists noticed that chickens living in stable social groups can recognize each other by facial features.

"As a trick at conferences I sometimes list these attributes without mentioning chickens," Dr Evans said. "People assume that I'm talking about monkeys."