Fear-related behavior of hens in cages: effects of rearing environment, age, and habituation.

At 18 weeks, pullets reared in floor pens and cages were placed in cages designed for laying hens. Tests were conducted for escape and avoidance behavior and for duration of tonic immobility at 23 and 40 weeks of age. Rearing environment effects were not detected for either measure. Paired comparisons did not reveal effects of age or habituation on duration of induced tonic immobility.