Research Article Received: 10 March 2013 Revised: 28 July 2013 Accepted article published: 20 August 2013 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/ps.3631 Habitat manipulation in lowland rice – coconut cropping systems of the Philippines – an effective rodent pest management strategy? Alexander M Stuart, a,b* Colin V Prescott b and Grant R Singleton a Abstract BACKGROUND: Reduction of vegetation height is recommended as a management strategy for controlling rodent pests of rice in South-east Asia, but there are limited field data to assess its effectiveness. The breeding biology of the main pest species of rodent in the Philippines, Rattus tanezumi, suggests that habitat manipulation in irrigated rice–coconut cropping systems may be an effective strategy to limit the quality and availability of their nesting habitat. The authors imposed a replicated manipulation of vegetation cover in adjacent coconut groves during a single rice-cropping season, and added artificial nest sites to facilitate capture and culling of young. RESULTS: Three trapping sessions in four rice fields (two treatments, two controls) adjacent to coconut groves led to the capture of 176 R. tanezumi, 12 Rattus exulans and seven Chrotomys mindorensis individuals. There was no significant difference in overall abundance between crop stages or between treatments, and there was no treatment effect on damage to tillers or rice yield. Only two R. tanezumi were caught at the artificial nest sites. CONCLUSION: Habitat manipulation to reduce the quality of R. tanezumi nesting habitat adjacent to rice fields is not effective as a lone rodent management tool in rice – coconut cropping systems. c  2013 Society of Chemical Industry Keywords: crop protection; habitat management; population dynamics; Philippines; Rattus tanezumi; rodent damage 1 INTRODUCTION In the Philippines and across South-east Asia, rodents are major agricultural pests, causing significant yield loss and loss of livelihood among smallholder farmers. 1 A recent survey of farmers in the Philippines revealed that rodents caused an average of 8.1–13.2% yield loss in rice and 3% yield loss in coconuts. 2 The high level of damage that rodents may cause to agricultural crops, especially rice, results in a need for their control. However, current methods appear to be inappropriate or poorly implemented. 2 One of the main issues compounding rodent management is that smallholder farmers have little income to spend on control methods. Thus, in order to manage pest rodents more effectively and in a sustainable manner, an integrated ecologically based pest management approach 3 should be developed that uses traditional rodent management methods and incorporates findings from research into the habitat use, population dynamics and breeding biology of the rodent pest species. There are several non-pest native rodent species present in lowland complex agroecosystems of the Philippines. 4 Thus, the use of an ecologically based approach could minimise non-target risks by targeting specific species and habitats at specific times. One strategy of ecologically based rodent management is to limit population growth by limiting the quality and availability of nesting habitat. This is likely to be a key limiting factor for Rattus tanezumi (Temminck), the main pest rodent species of rice and coconut in the lowland agroecosystems of Luzon, Philippines. 5 In lowland rice field ecosystems in Luzon, R. tanezumi breeds throughout the year, but with a peak in breeding activity during the ripening stages of the crop. 6,7 When two rice crops are cultivated in a year, two main breeding seasons occur. In lowland rice fields that are adjacent to coconut groves, the main breeding seasons commence during the booting stage of the rice crop and gradually decline after harvest. 8 Thus, the ideal time to limit the quality and availability of nesting habitat in a rice–coconut cropping system is during the generative stage of the rice crop – from the booting stage until the crop is harvested. A radiotracking study of R. tanezumi in rice – coconut systems in the Sierra Madre Biodiversity Corridor (SMBC), Luzon, Philippines, revealed that female R. tanezumi prefer to nest in coconut groves adjacent to rice fields, within close proximity to the edge of the rice field and almost exclusively where there is a good cover of understorey vegetation. 5 Therefore, habitat manipulation by reducing understorey vegetation cover in habitats adjacent to rice fields may be an effective strategy for limiting the growth of populations of rodent pests in rice – coconut cropping systems. A reduction in habitat quality through habitat management could increase pressure for resources and thus lead to an increase in ∗ Correspondence to: Alexander M Stuart, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines. E-mail: a.stuart@irri.org a International Rice Research Institute, Metro Manila, Philippines b School of Biological Sciences, The University of Reading, Berkshire, UK Pest Manag Sci (2013) www.soci.org c  2013 Society of Chemical Industry