Chicken food calls are functionally referential

Male chickens, Gallus gallus domesticus, usually produce characteristic 'food' calls upon discovering edible objects, and are more likely to do so in the presence of a hen. Food calling is thus dependent upon food and modulated by social context, which is consistent with the idea that hens respond because they anticipate a feeding opportunity. An alternative model suggests that female behaviour is not mediated by the predicted presence of food but rather by social information, such as a low probability of male aggression. We conducted two playback experiments to explore the type of information encoded in food-associated vocal signals. Isolated hens were played recorded food calls and we compared their responses with those evoked by ground alarm calls (which have similar acoustic characteristics) and by contact calls (which are produced under similar social circumstances). Hens responded to food call playbacks by fixating downwards with the frontal binocular field. This anticipatory feeding movement was specific to food calls and did not occur in either of the control conditions. Food calls also affected looking downwards selectively. There were no differences between the call types in their effects on social behaviour, such as approach and contact calling, nor were there differences in the nonspecific effects of sound playback, such as orienting towards the loudspeaker or increased locomotor activity. Chicken food calls appear to provide conspecifics with information about the presence of food. This property has not hitherto been demonstrated in any natural system of animal acoustic signals.