Data from: Acute peaks of testosterone suppress paternal care: evidence from individual hormonal reaction norms

A long-standing tenet of evolutionary endocrinology states that testosterone mediates the life-history trade-off between mating and paternal care. However, the support for a role of testosterone in suppressing paternal care is mixed: implantation studies in birds suggest that high-level testosterone implants suppress paternal care, but circulating levels of testosterone and paternal care are typically not correlated. Because any trade-off in real life must be realized with hormone levels that are within an individual’s reaction norm, it is crucial to show that natural changes in the hormone can modulate behavior. Here, we used GnRH injections to alter testosterone levels of free-living male black redstarts within each individuals’ hormonal reaction norm: experimental males resumed feeding their offspring later and showed a stronger suppression of offspring-feeding behavior than control males. For the first time, this study demonstrated that short-term peaks in testosterone within the hormonal reaction norm of individuals can suppress paternal behavior. Our findings reconcile previous seemingly contradictive evidence of implantation and correlation studies and demonstrate that the differential production of testosterone within the hormonal reaction norm of single individuals can indeed mediate the trade-off between mating and paternal care. On a broader note, our results suggest that natural and short peaks in testosterone can elicit adaptive behavioral changes