Individuality of laying hens within large groups and the relationship with temporal space usage

Consistent individual variation in animal behaviour has been identified as a major source of between-animal variability, affecting activity, immune responses, and health status. Despite these insights, laying hens are usually observed at the group-level with little consideration to individual differences in behaviour and their consequences. In a large-scale explorative study, the movement and location patterns of laying hens in a semi-commercial system was recorded by means of a RFID tracking system within four different areas (indoor, exterior winter-garden, yard and free range areas). Our methods allowed for characterisations of spatio-temporal patterns based on movements between areas as well as identifying non-random social associations based on co-occurrence at specific sites. We found that the laying hens developed a pronounced social network of differentiated individual associations that linked with spatio-temporal activity patterns. To characterise hens based on the level of similarity of ranging patterns, dissimilarity matrices were generated by Dynamic Time Warping. Cluster analysis suggests a small set of 4 - 5 distinct activity patterns with ranging patterns that were consistent over time and varied more between hens than within hens. Interestingly, similarity in daily activity patterns was highly correlated with social associations and closely associated birds became more similar with increasing age. To our knowledge, this is the first study linking animals' social niches with temporal activity patterns. The observed patterns and novel relationships identified revealed exciting opportunities to understand the complex behaviours of commercial laying hens and the observed variation in animal health, welfare, and productivity.