DescriptionSince providing care for offspring is costly, parents are assumed to be in an evolutionary conflict over the division of parental care duties, with each parent aiming to invest as little care as possible while forcing the partner to provide the majority of offspring care. However, the extent to which this assumption holds in real systems is poorly understood, partly because the underlying motivation for parental care may not be reflected adequately in behaviour. Therefore, measuring individual variation in the hormones underlying parental behaviours may provide important new insights into evolutionary conflicts between social partners. In addition, in many biparental species, social partners remain together for multiple breeding attempts; forcing a current partner to provide a super-optimal level of care may reduce that partner’s investment and survival in subsequent years. We therefore expect that selection will favour individuals who increase their relative contribution to parental care when mated with a partner who is likely to contribute substantial social benefits to future reproductive success. We tested these predictions in a captive population of black-headed gulls, Chroicocephalus ridibundus, where pair bond duration and behavioural compatibility between partners are known to affect reproductive success and thus a current partner’s future reproductive value. We used the hormone prolactin and its interaction with corticosterone as an endocrinological indicator of intrinsic motivation to provide parental care, and tested whether baseline and stress-induced levels of plasma prolactin (reflecting the motivation of the bird to stay at the nest after exposure to a stressor) were related to the social benefits an individual could expect to gain from its current partner in future breeding attempts. We argue that measuring individual variation in hormone secretion is a powerful way to test long-standing evolutionary theories, and highlight the importance of considering social context in understanding the evolution of reproductive investment.
|European Conference on Behavioural Biology 2022: All of life is social!
|Mate van erkenning
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