Rattus tanezumi (the Asian house rat) ,is the principal rodent pest of rice and coconut in Luzon,Philippines.To develop ecologically-based rodent management strategies for complex lowland agro-ecosystems,we conducted an 18-month trapping study in Aurora province,Luzon,to investigate the habitat use,population dynamics and breeding biology of R.tanezumi.Trapping was conducted monthly in rice monoculture,rice adjacent to coconut,coconut,agro-forest and forest habitats and trapped animals were measured,marked and assessed for breeding condition.The stage of the rice crop was a major factor influencing the habitat use and breeding biology of R.tanezumi.In rice fields,R.tanezumi abundance was highest during the tillering and booting stages of the rice crop and lowest during the seedling stage,whereas,in coconut groves,abundance was relatively high during the seedling stage of nearby rice crops.Peaks in breeding activity commenced from the booting stage of the crop and gradually declined after harvest,but breeding continued at a low level throughout the year.Contrary to the practices applied by rice farmers in the study region,the most effective time for lethal management is likely to be during the early stages of the rice crop,before the booting stage.Farmers generally apply control actions as individuals.We recommend coordinated community action.Continuous breeding throughout the year may necessitate two community campaigns per rice cropping season.To limit population growth,the most effective time to reduce nesting habitat is from the booting stage until harvest.The use of coconut habitat by R.tanezumi signifies that coconut groves adjacent to rice fields should also be considered when developing rodent management strategies for rice crops.