ABSTRACT
Chickens were domesticated in Asia about 8000 years ago. Despite many years of selection for production traits, the behavior of chickens is surprisingly similar to that of their wild ancestors, the red junglefowl.[1,2] Like junglefowl, chickens are highly social animals. They form dominance hierarchies (peck orders) and communicate using visual signals (appearance, posture) and vocalizations. In a naturalistic environment, they are exploratory and active, and they spend a large proportion of their day foraging for food. Significant time is also spent caring for the plumage, primarily by preening, during which oil from a gland at the base of the tail is worked through the feathers, and by dustbathing, during which loose material like dirt is worked through the feathers to absorb excess oils. The usual social group consists of a dominant rooster and a harem of 4-12 hens and their chicks. This group affiliates closely and feeds and roosts together. When the hens are ready to lay eggs, they separate themselves from the group and make a rudimentary nest in a secluded area, in which they lay and incubate. In the commercial environment, many of these behaviors are severely restricted, particularly for laying hens.
