Reproductive characteristics and growth of Zambian giant mole-rats, Cryptomys mechowi (Rodentia : Bathyergidae)

Information on reproduction, mortality rates and postnatal growth in giant mole-rats (Cryptomys mechowi) obtained from laboratory studies are presente d. Shortest period between two subsequent litters (indicating maximum gesta tion length) was 112 +/- 9 (89-118) days. Litter size was 2.6 +/- 1.1 (rang e 1-5, n=41) and increased with parity (i.e., number of births) of the moth er. Newborn pups (n = 74) weighed 19.6 +/- 2.9 (12.6-27.7) g. Body mass of neonates was neither correlated with sex nor with litter or family size. Mo rtality of juveniles within the first month after birth (total 61.3%) depen ded on body mass of neonates (smaller neonates were less viable), rather th an on sex, litter size, or family size (presence of helpers). More litters (66%) were burn during boreal autumn and winter than during spring and summ er (34%). While the mean litter size was roughly comparable in both periods (2.4 and 2.8, respectively), the juvenile mortality was higher in winter ( 73%) than in summer (42%). Sex ratio of neonates approached 0.54: 1 (male : female) and was independent of litter size, presence of helpers, and time of conception (post partum or post lactationem). Some behavioural elements of the development in pups are described. Growth rate of juveniles during t he first 180 days after birth was about 0.615 g/day for both males and fema les. Growth parameters according to the Gompertz growth model and growth cu rves are presented. All parameters are compared and contrasted with those o f other bathyergid mole-rats, and perspectives for further studies are give n.