Reproductive suppression in female Damaraland mole-rats Cryptomys damarensis: dominant control or self-restraint?

Colonies of Damaraland mole-rats Cryptomys damarensis exhibit a high reprod uctive skew Typically one female breeds and the others are anovulatory. Two models, the dominant control model (DCM) and the self-restraint model (SRM ), have been proposed to account for this reproductive suppression. The DCM proposes that suppression is under the control of the dominant breeder and is imposed by mechanisms such as aggression, pheromones and interference w ith copulation, whereas the SRM does not involve aggression directed toward s non-breeders and may function in order to minimize inbreeding. We investi gated potential proximate mechanisms involved in the suppression of females in a series of experiments. Socially induced stress through aggression did not appear to be responsible for anovulation. Nor did breeders actively in terfere with subordinate copulation. Females were physiologically suppresse d when housed in intact colonies. However, as predicted by the DCM, they di d not become reproductively active when removed from the presence of breede rs. We found no evidence that pheromonal cues block ovulation. We suggest t hat the SRM is the basic model found in the Damaraland mole-rat and that se lf-restraint functions in order to minimize inbreeding by restricting repro duction until an unrelated male is present. This would explain the rapid on set of reproductive activation in females when paired with an unrelated mal e, as demonstrated ill this study.