Decisions about foraging and risk trade-offs in chickens are associated with individual somatic response profiles

An important decision for individuals of many species is how to balance the need to forage against encounters with potential dangers. The proximate emotional cues that animals use to make complex foraging decisions are poorly known. We therefore investigated how behavioural and physiological responses to three different environments were linked with foraging decisions in 72 laying hens, Gallus gallus. The environments were F (additional foraging materials), FR (additional foraging materials and a cue indicating risk of predation) and R (risk cue only). Hens spent 3 weeks in one environment, followed by 3 weeks in another. The two environments were then linked with a tunnel and, on seven occasions, the hens chose one of them. The entire procedure was repeated twice so that the hens’ responses and choices were assessed for every possible pair of environments. Across the experiment we predicted transitive preferences of the form F > FR > R. We modelled associations between responses and decisions using a hierarchical statistical model. Overall, hens preferred environments in the pattern predicted, but with considerable interindividual variation. Hens chose environments associated with lower stress (specifically lower corticosterone levels and lower faecal water content) in this foraging context, suggesting they could use emotional state variables as a proximate method of choosing between complex environments. Positive choice was further associated with less head shaking, self-scratching, standing alert and feeding, and more foraging and sitting alert during a novel object test. Our results, alongside previous work, suggest that some of these responses are good general indicators of emotional valence.