Comparison of multimammate mouse (Mastomys natalensis) demography in monoculture and mosaic agricultural habitat: implications for pest management

Extensive monocultures are often believed to be more vulnerable to attacks by insect pests than crops in a heterogeneous landscape. In monocultures the insect pests find abundant resources when the crops are in the susceptible stage and they migrate or enter diapause when the crop is removed. For rodents, escaping from temporarily poor conditions is relatively more difficult, and therefore we predicted that a population of rodent pests in a monoculture with synchronised periods of absence of the field crop, would do less well when compared with a population in a heterogeneous landscape. The multimammate mouse (Mastomys natalensis) is a major pest in rural areas throughout sub-Saharan Africa. It appears difficult to control since it has an opportunistic diet and the capacity for explosive population growth. We compared demographic rates between a population in an extensive maize monoculture and a population in a mixed landscape of smaller maize fields. We used data from a 4-year monthly capture¿recapture study. Time series of abundance estimates for the two sites showed remarkable synchrony. Timing and duration of reproduction were comparable, although more females were observed to mature in the mosaic compared to the monoculture. The probability of capture was higher in the mosaic structured grid for both the subadult and adult part of the population. The model selection procedure demonstrated that a model without an effect of habitat in both survival and seniority received most support from the data. No differences in the multimammate mouse demography between the monoculture and mosaic structured habitat were observed which had a substantial impact on population dynamics. This means that rodent management options in both agricultural systems could focus on the same aspects of rodent ecology