POPULATION MANAGEMENT of RODENT PESTS through INTENSIVE TRAPPING inside RURAL HOUSEHOLDS in MOZAMBIQUE

Abstract:
Field trials involving seventy rural households from three villages in Mozambique were established to test whether intensive daily trapping inside household-level food stores could effectively reduce rodent pest populations. The main species caught inside dwellings where food was stored were Rattus rattus [alexandrinus], comprising 74.3% of rodents caught over the year, followed byMastomys natalensis (20.1%) and Saccostomus campestris (5.6%). Baseline surveys showed that households using 10 break- back traps caught an average of 1.2 ± 0.37 rats/day (mean ± sem). Annual trials whereby half of the selected dwellings in each village continuously trapped every day with 10 traps were able to reduce the number of rodents in their houses by 50–70% compared to the non-treatment group of farmers who only trapped for three days every eight weeks. The population reduction caused by intensive trapping was maintained over the remaining duration of the trial. Farmers who intensively trapped rodents (treatment group) caught an average 1.27 ± 0.43 rats/day, whereas non-treatment group farmers caught an average of 2.95 ± 0.71 rats/day. The number of rats and the ratio of species caught by treatment farmers varied over an annual cycle related to seasonal and anthropogenic factors. Variation in the number of rats caught among farmers intensively trapping within a village and variation among villages was significant, showing Morrumbala to have the highest rodent population density (2.7 ± 0.15 rats/day, mean ± sem) followed by Gurué (1.0 ± 0.14 rats/day) and Namacurra (0.3 ± 0.07 rats/day). Average daily trap catch initially increased in Morrumbala, then decreased as the storage season progressed, whereas populations continually decreased in Namacurra and Gurué. The average weight of rodents caught by treatment farmers was reduced by more than 30% compared to the non-treatment, falling from 69.5 ± 3.26 g to 41.9 ± 2.02 g. We conclude that intensive trapping can constrain rodent populations that utilise stored grain stocks within rural African households, thereby reducing grain losses. The implications of these results are discussed in the context of implementing ecologically-based rodent management strategies for poor rural communities in Africa.