Reproduction and postnatal development in the bush Karoo rat Otomys unisulcatus (Muridae, Otomyinae)

Reproduction and postnatal development of the southern African bush Karoo rat Otomys unisulcatus was studied in the laboratory. Fifty‐one litters were obtained from 17 pairs, with a mean litter size of 2.09, reproductive effort of 0.58 and gestation period of 37 days. Neonates weighed 6.1–9.6 g and were semi‐precocial. Weaning began as early as 8 days of age, and the age at first reproduction was 6 weeks in males and 5 weeks in females. Compared to its congeners, O. unisulcatus has small litters of semi‐precocial young which undergo rapid postnatal development, and contrary to expectations displays several K ‐selected reproductive characteristics. The reproductive biology and postnatal development of the bush Karoo appears to reflect a compromise between exploiting sporadically abundant resources and the occupation of stick lodges, which may provide a favourable microclimate to buffer the harsh external climate.