The Namaqua dune mole-rat Bathyergus janetta breeds seasonally, producing up to two litters during the early summer in the Cape. Females exhibit elevated urinary progesterone and oestradiol-17β concentrations and males raised concentrations of testosterone, these correlate with the onset of the seasonal winter rainfall. The rains moisten the soil allowing excavation and provide the mole-rats with the opportunity not only to extend burrow systems but also to search for mates. An increased incidence of hindfoot drumming and visitations to neighbouring burrow systems occurs during this period. Plural occupancy of burrows by adult mole-rats was found during the onset of the winter, and pups, lactating and pregnant females were caught at the end of October and November (early Cape summer). Pups develop rapidly and their eyes open after c. 1 week. Pup body mass increases exponentially from birth to about 70 days. Inter-sibling aggression increases progressively and after c. 60 days captive-born pups had to be separated, suggesting that in the wild they would have dispersed.