Inbreeding avoidance and reproductive skew in a cooperative mammal

In animal social groups, socially subordinate individuals frequently show l ow reproductive success or completely fail to breed. This suppression of su bordinate reproduction is currently typically attributed to control by domi nant individuals. However, subordinates in cooperative groups often lack ac cess to unrelated mates, and an alternative possibility is that their repro duction is limited by inbreeding avoidance. Using the eusocial Damaraland m ole-rat Cryptomys damarensis, this paper provides the first experimental ev idence! to our knowledge, for this explanation. Subordinate, non-breeding f emale mole-rats were given access to unrelated mates while remaining in the presence of dominant females, and many became reproductively active soon a fter unrelated males were introduced. Inbreeding avoidance and the availabi lity of unrelated mates provides a plausible and untested explanation for v ariation in reproductive skew across animal societies.