Mediating factors in chick social pecking: 1. Effects of isolation, imprinting, and peer contact

Abstract

Two experiments examined the influence of periods of social isolation on rates of intersubject pecking in pairs of domestic chicks. Of central interest was the effect of an imprinting condition wherein single birds were reared with either a red or green Styrofoam object. In the first experiment, imprinted subjects were given social pecking tests in the absence of the imprinting object, while in the second study the tests for social pecking were conducted in the presence of one of the imprinting objects. In the latter test the object was familiar to one bud of a pair, but was novel to the other animal. The results of both experiments showed that the rate of intersubject pecking of the imprinted subjects was intermediate to, and statistically different from both the low pecking rate of chicks reared in pairs and the high pecking rate of chicks reared in total isolation. The presence of a familiar object during tests in the second study seemed to serve as a secure base since chicks that had been reared with that object exhibited more social pecking than did chicks that were unfamiliar with the object. However, regardless of the provision of the object the social pecking of the imprinted chicks again fell on a point intermediate to the other groups. Hypotheses concerning a) intolerance of figureground movement and b) sheer stress of isolation were advanced to account for these results.