Representational signalling in birds

CHRISTOPHER S. EVANS & LINDA EVANS

Biology Letters, 2007, 3: 8-11

Some animals give specific calls when they discover food or detect a particular type of predator.  Companions respond with food-searching behaviour or by adopting appropriate escape responses.  These signals thus seem to denote objects in the environment, but this specific mechanism has only been demonstrated for monkey alarm calls.   We manipulated whether fowl (Gallus gallus) had recently found a small quantity of preferred food and then tested for a specific interaction between this event and their subsequent response to playback of food calls.  In one treatment, food calls thus potentially provided information about the immediate environment, while in the other the putative message was redundant with individual experience.  Food calls evoked substrate searching, but only if the hens had not recently discovered food.  An identical manipulation had no effect on responses to an acoustically matched control call.  These results show that chicken food calls are representational signals: they stimulate retrieval of information about a class of external events.  This is the first such demonstration for any non-primate species.  Representational signalling is hence more taxonomically widespread than has previously been thought, suggesting that it may be the product of common social factors, rather than an attribute of a particular phylogenetic lineage.