Timing of maternal nest building and perinatal offspring survival in a group-living small mammal

Maternal care frequently includes the construction of a burrow or nest where mothers will raise their young. Delays in the timing of such complex sequences of building behavior might potentially interfere with mothers’ successful reproduction. By analyzing a long-term data set (11 years) from a study on European rabbits Oryctolagus cuniculus, we tested whether late maternal burrow and nest building increases the occurrence of perinatal offspring mortality. Additionally, we aimed to identify causes for the occurrence of such late burrow and nest building behavior. In the majority of cases, mothers dug their nursery burrow and constructed a grass nest inside well before the last 24 h prior to parturition. During the last pre-partum day, mothers usually lined the nests with their abdominal hair. However, when mothers carried out of all these activities during the last 24 h pre-partum (“late burrow and nest building”), perinatal mortality was significantly increased. Social constraints might have affected the temporal aspects of females’ display of nest building. Thus, in social groups occupying smaller territories, late burrow and nest building occurred with a significantly higher probability when several females of that group gave birth within a period of a few days (“concurrent parturition”). Behavioral observations suggested that concurrent parturition was associated a higher level of intra-sexual competition, since a significantly increased frequency of agonistic interactions among females was observed in these conditions. The results suggest a mechanism by which the mothers’ social environment influences perinatal mortality, thus adding to our knowledge on drivers of maternal fitness. SIGNIFICANCE STATEMENT: Differences in the timing of maternal care behavior can strongly affect offspring survival. We investigated this link in a long-term study of a colony of European rabbits. In this species, the young are born and raised in nests situated in nursery burrows dug by the mother. Females which dug their burrow and constructed the nest during the last night before giving birth showed a higher perinatal offspring mortality than mothers that dug their burrow earlier. Furthermore, we explored potential causes of such delays in the timing of burrow and nest construction. Agonistic social interactions between females were increased when different females of a group reproduced at around the same time. Overall, the findings support the conclusion that competition for breeding resources, in particular within smaller group territories, was an important driver for delays in maternal burrow and nest building.