Protective mother hens: cognitive influences on the avian maternal response

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We previously demonstrated that domestic hens, Gallus gallus domesticus, show behavioural and physiological responses when witnessing mild chick distress, and possess the underlying foundations of emotional empathy. However, no studies have determined how cognitive influences affect empathic processes in birds. A fundamental question is whether a mother hen's response to chick distress is mediated by her knowledge about the situation or by chick distress cues. We therefore investigated how manipulating hen and chick knowledge influences hens' responses to chick distress. Each hen's brood of chicks was split into three groups, based on whether they had the same, opposite or no knowledge about a potentially threatening situation (environmental cues signalling air puff administration). We compared hens' behavioural, vocal and physiological responses (heart rate, heart rate variability and surface body temperature) to actual and perceived threat to their chicks. Hens increased maternal vocalizations and walking, and decreased preening, when they perceived their chicks to be threatened, regardless of the chicks' reactions to the situation. Hens exhibited signs of stress-induced hyperthermia only when their perception of threat was in accordance with that of their chicks. Chick behaviour was influenced by the hens' expectations, with all chick groups spending more time distress vocalizing and less time preening when in the environment that the hen associated with threat. We conclude that the protective maternal response of domestic hens is not solely driven by chick distress cues; rather, hens integrate these with their own knowledge to produce a potentially adaptive, flexible and context-dependent response.