The Effects of Offspring Social Isolation

Family life is a widespread phenomenon in the animal kingdom and can be found in many taxa. While parent-offspring interactions are a key component of family life, family life entails much more multifaceted interactions between family members. Sibling cooperation, for example, is a key feature of eusociality. Recently emerging views hypothesize that sibling cooperation was a major driver in the early evolution of social and family life. Sibling cooperative behaviour can range from active forms of cooperation, such as food sharing, to more indirect forms of cooperation, for example delayed fletching of older and more independent chicks in the common house wren. While the effects of isolated family interactions have been extensively studied, interplays between different family interactions, especially in subsocial species, have gained little attention. However, the understanding of these interplays in subsocial species can provide us a great insight into the early evolution of social and family life. Here, we investigated family and sibling interactions in the absence and presence of parental care in the subsocial burying beetle Nicrophorus vespilloides, a species with facultative brood care, whereby offspring profits from the presence of parents but can also survive and develop in the absence of parental care. Recent studies suggest that siblings of this species cooperate in the absence of parental care to compensate for the parents’ absence. The specific mechanism(s) of sibling cooperation in N. vespilloides are, however, unclear. It is also unknown how sibling interactions are influenced by the parents. Our results confirm that sibling cooperation indeed occurs in the absence of parents. However, also in the presence of parents, offspring profit from siblings, though this advantage is only observable during early development. With that, our results highlight the major role of sibling cooperation in the early evolution of family life.