Restraint, fear, and distress in Japanese quail genetically selected for long or short tonic immobility reactions.

Japanese quail genetically selected for long (LTI) rather than short (STI) tonic immobility reactions showed more pronounced overt fear-responses in a number of putatively frightening situations. Greater fear has also been found in Japanese quail selected, in an independent program, for exaggerated (HS, high stress) rather than reduced (LS, low stress) plasma corticosterone response to brief mechanical restraint. The present study examined tonic immobility (TI) and adrenocortical responses in male and female quail of the LTI, STI and CON (control) lines which had either remained undisturbed or had been briefly exposed to a mechanical restraint stressor similar to that used for selection of the HS and LS lines. Behavioral strategies during restraint differed across lines, i.e., struggling followed the pattern STI > CON > LTI. The LTI quail showed more pronounced TI reactions than did CON and STI birds. Mechanical restraint prolonged subsequent TI responses and markedly elevated plasma corticosterone concentrations in all lines, but there were no line x treatment interactions. The results are discussed in terms of the parallels between the four selected lines and of the likelihood that the independent selection programs may have affected the same intervening variable.