Data from: Sex differences in the drivers of reproductive skew in a cooperative breeder

Here we use long-term genetic and observational data to examine factors affecting reproductive skew in the high-skew cooperatively breeding southern pied babbler (Turdoides bicolor). When subordinates can breed, skew remains high, suggesting factors additional to inbreeding avoidance drive skew. Subordinate females are more likely to compete to breed when older or when ecological constraints on dispersal are high, but heavy subordinate females are more likely to successfully breed.

Subordinate males are more likely to compete when they are older, during high ecological constraints, or when they are related to the dominant male, but only the presence of within-group unrelated subordinate females predicts subordinate male breeding success. Reproductive skew is not driven by reproductive effort, but by forces such as intrinsic physical limitations and intra-sexual conflict (for females), or female mate choice, male mate-guarding and potentially reproductive restraint (for males).

Ecological conditions or ‘outside options’ affect the occurrence of reproductive conflict, supporting predictions of recent synthetic skew models. Inbreeding avoidance together with competition for access to reproduction may generate high skew in animal societies, and disparate processes may be operating to maintain male vs. female reproductive skew in the same species. Usage notes comp females Factors associated with competition among females comp males Factors associated with competition among males reprod success females Factors associated with breeding success among females reprod success males Factors associated with breeding success among males