Gender differences in the inhibitory effects of a reduction in ambient temperature and a reduction in food quantity on reproduction in the Southern African rodent, Rhabdomys pumilio

The effects of a reduction in ambient temperature (from 26 degreesC to 15 d egreesC) and a 10% reduction in daily food consumption on reproductively ac tive male and female four-striped field mice (Rhabdomys pumilio) were inves tigated. In male R. pumilio, both reduced ambient temperature and a reducti on in food quantity had an inhibitory effect on spermatogenesis and on size of the reproductive organs, and this was greatest when the two factors wer e combined and the effect of fat was removed. Female R. pumilio responded d ifferently and reproduction was inhibited by a reduction in food quantity, irrespective of ambient temperature. The masses of the ovaries and uterus, the numbers of developing follicles and corpora lutea, and the development of the uterine wall were all reduced by food deprivation at 26 degreesC to levels similar to those that resulted from a reduction in ambient temperatu re to 15 degreesC with a reduction in food quantity. It is concluded that r eproduction in R. pumilio from the Eastern Cape Province of South Africa is opportunistic, that reproduction will be inhibited by an energetic challen ge and that there is sexual dimorphism in the response to ambient temperatu re and food supply.