Effects of group rearing on the control exerted by an imprinting stimulus

Abstract

Prior research suggests that group rearing may attenuate a young bird’s tendency to approach and follow an imprinting stimulus. The present work examined the effect of group rearing on a different measure of attachment, suppression by the imprinting stimulus of distress calling induced by abrupt reductions in group size. In Experiment 1, ducklings were reared in groups of 12 or 3 over Days 1–6 posthatch, and each group received a total of 3.5 h of exposure to an imprinting stimulus. Subsequent tests revealed that, when the groups of ducklings were separated into smaller subgroups: (1) the fewer the ducklings in a subgroup, the more distress calls emitted; (2) a given number of birds separated from a larger group emitted more distress calls than an equal number from a smaller group; and (3) regardless of the subgroup size, fewer distress calls occurred when the imprinting stimulus was present than when it was absent. A second experiment revealed that when a group of 12 birds was first confronted with an imprinting stimulus on Day 6 posthatch, they reacted with an increase in distress calling and corner huddling (an aversive reaction). After several hours of exposure to the stimulus, however, its presence exerted a powerful suppressive effect on distress calling. It is concluded that the social bonds between the members of a brood do not preclude the formation of a social attachment to an imprinting stimulus subsequently encountered.