Open-field and tonic immobility responses in domestic chicks of two genetic lines differing in their propensity to feather peck.

1. The open-field and tonic immobility reactions of female domestic chicks of 2 genetic lines which showed high (HP) or low (LP) levels of feather pecking were compared. 2. Chicks of the LP line showed less freezing, and vocalised and walked sooner and more in the open field than did their HP counterparts. 3. There were no differences between lines in the durations of their tonic immobility responses, at least in the present study. 4. The pattern of results may reflect line divergence in underlying social motivation rather than fearfulness.