Survival and maturation rates of the African rodent, Mastomys natalensis: density-dependence and rainfall.

Survival and maturation rates of female Mastomys natalensis were analysed based on a ten-year monthly capture-recapture data set. We investigated whether direct and delayed density dependent and independent (rainfall) variables accounted for the considerable variation in demographic traits. It was estimated that seasonal and annual covariates accounted for respectively 29 and 26% of the total variation in maturation rates and respectively 17 and 11% of the variation in survival rates. Explaining the between-year differences in maturation rates with annual past rainfall or density did not improve the model fit. On the other hand we showed that maturation rates were correlated negatively with density the previous month and positively to cumulative rainfall over the past three months. Survival estimates of both adults and subadults varied seasonally, with higher estimates during the increase phase (dry season). The subadults were characterised by a very high survival rate (> 0.95) during this phase. In the decrease phase only minor differences were found between survival rates of subadults and adults. We found that 39% of the between-year variation in survival can be explained by accumulated rainfall over the past year.