In many animal species, mothers expose their embryos to maternal hormones. This provides a powerful pathway for affecting offspring phenotype and a potential mechanism for adaptive nongenomic inheritance.
This has been studied extensively in birds because the embryo develops outside the mother's body, facilitating experimental studies. Some studies have demonstrated that maternal yolk testosterone (T) can have long-lasting effects into the period after fledging. However, these results are based on offspring in the juvenile stage or their first breeding season only. The lack of data further into adulthood limits a better assessment of the fitness consequences of prenatal T. In a series of previous experiments in the rock pigeon, Columba livia, we manipulated yolk T levels using oil-injected eggs as controls. In the present study, we examined the reproductive behaviour of birds from these eggs when they were 1-3 years old and housed together in a large aviary. Our results showed that males from T-injected eggs were less aggressive and females from T-injected eggs laid lighter eggs than controls. Moreover, the experimental birds showed strongly disassortative mating with respect to hormone treatment. There were no indications of treatment effects on the process of sexual differentiation. Our results indicate that the effects of prenatal T do not diminish over age and may last far into adulthood, which should be taken into account in assessing the fitness consequences of maternal hormones. They may also stimulate new physiological and neurobiological studies on the mechanisms underlying such long-lasting effects of prenatal T exposure.