Responses to isolation in Japanese quail genetically selected for high or low sociality

The adrenocortical, behavioral, and leucocytic responses to isolation, for 1, 3, or 72 h, of 7-10-day-old Japanese quail chicks, of lines selected for high (HSR) or low (LSR) levels of social reinstatement (SR) behavior, were studied. Isolation had no effect on plasma corticosterone levels of heterophil/lymphocyte measures in LSR line chicks. Conversely, circulating corticosterone levels were increased after 1 h of isolation in the HSR line, although they fell to control levels thereafter. Heterophil/lymphocyte ratios of HSR line chicks were also increased after 3 h of isolation but decreased to control levels thereafter. Isolated HSR line chicks were consistently more active and showed more peeping and jumping than LSR line chicks in which sitting and lying were more frequent. However, no such behavioral divergence was observed when HSR and LSR line chicks were housed in same-line groups. These results indicate that selection for SR behavior has influenced both underlying social motivation and responses to short-term isolation. Social separation appeared to be more stressful for HSR than LSR line chicks.