Adrenocortical response to mating, social interaction and restraint in the female Japanese quail.

In some species, the act of mating may be the only occasion when a female judges the male and the course of the sexual encounter might influence forms of maternal investment that are mediated by hormonal pathways. Despite the growing interest in fitness consequences of acute adrenocortical responses, it has not been determined to what extent the act of mating provokes such responses in females. We used female Japanese quail (Coturnix japonica) to determine to what extent any increase in corticosterone (CORT) is specific to actually mating with a male compared to visual and auditory contact with a male, and compared to social interaction with a female. We also asked if greater mating experience decreases the CORT response. We assessed how body condition of the individuals and their behavior during testing contributed to the variation in CORT response. As an additional reference for CORT increase we used a restraint procedure which resulted in the highest CORT. Our results show that females mating with a male have plasma CORT concentrations significantly increased from the baseline, which is not the case in females interacting with a male without the possibility of mating. Greater previous mating experience does not affect the CORT change caused by sexual interaction. Interestingly, social interaction with a female elicited a similar CORT response as mating with a male, which suggests that the effect on CORT was due to direct social interactions per se and not specific to the act of mating. Behavior during social and sexual interactions did not predict the CORT response, but larger females exhibited lower baseline and response CORT concentrations. We suggest that the lesser adrenocortical response of larger females might be related to their better control of the course of mating and might help them to adjust their reproductive investment, as reported in earlier studies.