Visual cues for suppressing isolation-induced distress calls in quail chicks

Abstract

When socially isolated from siblings, newly hatched chicks emit distress calls at a high frequency. As a step toward identifying brain mechanisms responsible for recognition of conspecifics, we analyzed sensory cues critical for suppressing distress calls in socially isolated quail chicks at post-hatch day 2 to 4. Each subject of wild-type chicks was reared with another wild-type companion chick for 1-2 nights before tests. As the first step, we found that distress call was completely suppressed when accompanied by another wild-type chick, irrespective of whether the subject had previously been familiarized with the chick or not. When paired with an albino chick, on the other hand, the subject emitted significantly more calls, suggesting that the wild-type plumage is important. As the next step, in search of the critical sensory modality, we found that visual display of a conspecific chick suppressed the distress call even without accompanying acoustical stimuli. On the other hand, the acoustical stimuli alone were without effects. Olfactory as well as tactile sensations also proved irrelevant. As the final step, we tried to identify the significant sub-modalities in the visual images of conspecifics. Degraded visual image of a moving chick (degraded in fine details) caused a significant but incomplete suppression, whereas an anesthetized chick was without effects. On the other hand, distress calls were completely suppressed even without behavioral correspondence or exact plumage coloration. All of these data suggest that visual image of a moving chick should be given at a high spatial resolution, and wild-type plumage pattern might provide important visual cues.