Reproductive biology of the southern African ice rat

Abstract

Reproduction and the postnatal development of nine litters of the southern African ice rat Otomys sloggetti robertsi Hewitt, 1927 were studied in the laboratory. Parturition and lactation occurred in the presence of up to seven cage-mates, reflecting the colonial social organization of O. s. robertsi. Mean litter size was 1.44, reproductive effort 0.53, gestation period 38 days and fecundity approximately six young p.a. Newborn young weighed 10.6 — — 12.2 g and were semi-precocial. Early behaviour was dominated by nipple-clinging. Weaning occurred at 16 days old, and sexual maturity at 16 weeks in males and 11 weeks in females. Compared to O. s. robertsi, young of the vlei rat O. irroratus (Brants, 1827) are born more precocial and develop more rapidly. The microthermal environment of O. s. robertsi is harsh but predictable, and the subspecies is K-selected in terms of most reproductive parameters. Reduced fecundity and AT-selection is further attributable to the microhabitat stabilizing effects of nesting, social huddling and food hoarding in an underground burrow.