The impact of breeding experience and social status on group interactions and fitness in a communally breeding species

In group breeding species, not only prior breeding experiences, but also an individual's social status and that of the group members it interacts with, may influence an individual's future behaviour and fitness. Here, we report an experimental study on the facultatively communal breeding burying beetles, Nicrophorus vespilloides, in which we tested the combined effects of prior breeding experience and dominance status (dominant vs. subordinate) of focal individuals and those of other group members on aggressive interactions, parental investment and fitness during a future breeding event. In the presence of inexperienced subordinates, there was less aggressiveness towards experienced dominants than to inexperienced dominants, which resulted in a lower injury degree of dominants. Compared to inexperienced dominant or subordinate individuals, experienced dominants with prior breeding experience increased their parental investment, whereas experienced subordinates reduced their parental investment and by doing so avoid the escalation of aggressive interactions. Consequently, dominants may benefit from the presence of experienced subordinates because they gain enhanced benefits in reproduction, or suffer less from aggressive interactions with others. Our results highlight the importance of an individual's own breeding experience and social status and that of other group members for mediating individual behaviour and social interactions in groups resulting in higher net fitness.