Ease of capture in Japanese quail of two lines divergently selected for adrenocortical response to immobilization.

Divergent lines of Japanese quail have been genetically selected over several generations for a reduced (low stress, LS) or an exaggerated (high stress, HS) plasma corticosterone response to brief mechanical restraint. Female quail were housed in one mixed-line group (18LS + 18 HS) in one of the top-tier compartments of a brooder. At 32 d of age, the quail were removed individually by the experimenter, their identity and position in the order of capture were noted, and then they were placed in a separate compartment. Following brief respites, this procedure was repeated on 16 occasions. No differences were found between HS and LS quail in their ease of capture and no linear trends were apparent upon repeated testing of either strain. These findings have positive connotations for management and welfare because, although selection for a reduced adrenocortical stress response to restraint has apparently been accompanied by reduced fearfulness, it has not resulted in a potential and undesirable increase in the difficulty of capture and handling. Further, the significant tendencies found within and across lines for individual birds to be caught at similar stages of each trial has important implications for behavioral studies that involve putatively random sampling of a population.