Reproduction and Development of Rattus exulans (Peal) and Rattus tiomanicus (Miller)

Abstract

Growth and development were studied in the polynesian rat (Rattus exulans (peal) caught in Thailand, and the wood rat (Rattus tiomanicus (Miller) caught in Malaysia. The studies were undertaken under laboratory conditions in 1981 at Bonn University, West Germany.
Non lactating gestation of both rat species was 21 - 22 days; postpartum estrus also occurred in both species. Lactation prolonged gestation of R. exulans by 1 - 6 days and in R. tiomanicus by 1 - 3 days. Mean litter size of R. exulans and R. tiomanicus was 4.9 and 4.7 , respectively. the sex ratio in the litter of both species was equal. The relationship between litter size and weight of the female for R. tiomanicus 84 days. the youngest mature males of R. exulans and R. tiomanicus were 79 and 163 days of age, respectively.
Growth as measured by weight and linear dimensions was most repid in the first four weeks for both species. Sight and hearing had developed by the end of the second week. Sexual dimorphism in weight of R. exulans resulted from the continued growth of males after the seventh week, relative to a reduction in the growth of females. However, in R. tiomanicus there was no significant difference in weight between the sexes after 14 weeks.