Lower redness of the facial skin is a marker of a positive human-hen relationship

Abstract

International audienceIn certain mammals, facial expressions are reliable markers of the emotional state of an individual. In humans andparrots, emotional stimuli can induce a rapid change of face colour that is linked to blood flow. The aim of this studywas to test whether the redness of the face in domestic hens could be used as an emotional marker in the context of thehuman-hen relationship. Two groups of hens (Sussex) were studied: a group habituated to a human with daily positiveinteraction (n=13) and a non-habituated group (n=12). Behaviour and skin colour of wattles, cheeks, ear lobes andcomb were analysed from two video-recorded tests (novel environment and reactivity to human tests) conducted after5 and 6 weeks of habituation. In the novel environment test, usually used for testing general underlying fearfulness,the hens were tested alone in an unknown environment. In the reactivity to human test, the hens were tested againin this environment but with the familiar human sitting inside. The human presence should only be stressful for thenon-habituated group. As expected, the behaviour of the two groups did not differ during the novel environment test.During the reactivity to human test, the habituated hens were more relaxed than the non-habituated hens: they tooktheir first step faster (P=0.03), came faster into contact with the human (P=0.03), explored him longer (P=0.0003)and displayed more comfort behaviours (P=0.01). Face redness differed between the two groups during only thereactivity to human test: lower redness was observed in habituated hens for 3 out of the 4 regions (wattles P=0.01,cheeks P<0.0001, ear lobes P=0.0003). These results show that more relaxed hens are less red, thus face rednesscould be a reliable marker of the quality of the human-hen relationship. As such, it could be used as a tool for humanto infer the emotional state of hens and more broadly, to evaluate their welfare