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BACKGROUND: The mechanisms that regulate multi‐annual population dynamics of rodent pest species of cereal crops is often unknown. Better knowledge of such aspects can aid pest management and in turn improve food security and human health. The patterns and processes of the population dynamics of Rattus argentiventer, in rice fields of Indonesia, and Rattus tanezumi, in rice fields of the Philippines were assessed in this article. RESULTS: The meta‐analysis of trapping data over 20 years in Indonesia, and 16 years in the Philippines indicated that rodent populations in rice fields did not show a regular multi‐annual pattern. Rattus argentiventer populations in Indonesia responded to less rainfall from the current year. Rattus tanezumi populations in the Philippines responded positively to both rainfall and rainfall anomaly with a 1‐year time lag. CONCLUSIONS: Our study of long‐term population data indicates that certain combinations of rainfall parameters could be useful to predict years when there is higher rodent abundance in rice fields. The key rodent pest species in rice fields in Indonesia (R. argentiventer) and the Philippines (R. tanezumi) differ, and the populations of each species respond differently to rainfall anomalies. Other factors such as crop cover and water availability may also be important and should be considered in future work. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Food security is a major concern at a global level. The impacts of rodents pre- and post-harvest are legendary, as too are their incursions on the day-to-day lives of people. As vertebrate pest managers we need to move beyond the rhetoric and provide effective management approaches. If on an annual basis we can reduce by 5% the food that rodents eat and spoil globally, then this could save 70 million tons of grain. From the 1960s to the mid 1990s the dominant paradigm for rodent control was the widespread use of chemical rodenticides. Rodent biologists were forced to rethink this reliance on chemical rodenticides because of human health and safety issues, lack of efficacy, detrimental effects on non-target species, and the development of resistance to the anticoagulant rodenticides. Some 15 years ago, ecologically-based rodent management (EBRM) was formally described based on adaptive research conducted to manage irruptions of mouse populations in Australia and rats in Southeast Asia. EBRM builds on foundation work conducted in the 1940s and 1950s by ecologists such as Elton, Chitty, and Davis; research that was marginalized with the advent of cheap and effective rodenticides. EBRM has had a significant impact since its formulation: it has been formally adopted by the governments of Indonesia and Vietnam as their national policy for rodent management in agricultural systems, and is the main rodent management paradigm in at least 30 countries. A challenge is to address not only chronic rodent problems in agricultural landscapes but also the acute outbreaks that cause tremendous impacts on rural communities. An important component of EBRM has been the incorporation of sociological research. I provide a retrospective view of what has been achieved by ecologists and sociologists over the past 15 years, identify countries where progress has been promising, and then provide thoughts on some promising global research challenges.

About 70% of the current energy intake of the human population in southeast Asia is met by rice. Rats, especially the ricefield rat, Rattus argentiventer, cause significant pre- and post-harvest losses in rice-based agro-ecosystems of southeast Asia and therefore require appropriate management. Current management practices focus on culling animals when populations are high and after significant damage has already occurred. The use of legal and illegal poisons poses a considerable threat to non-target species and humans. This is of particular concern in regions where rats are often consumed by humans to provide an important protein supplement to their diet. During the last seven years, CSIRO’s rodent research group has tested and refined several methods aimed at decreasing pre-harvest rodent damage in cooperation with the Indonesian Research Institute for Rice and the Vietnamese National Institute for Plant Protection. These methods include exclusion of rats by fencing and physical control by trap-barrier systems with lure crops. The effects of these technologies were investigated regarding the regulation of rat numbers (physical control), damage (exclusion, physical control) and yield (physical control). The results are promising, indicating yield increase, of up to 20% in some cases. Integration of these methods with improved field sanitation, crop synchronisation and more efficient timing of other physical methods of control should result in pronounced increases in yield and improved cost effectiveness. Our approach is contingent on a strong understanding of the ecology of specific rodent pests. Measures of success besides decrease in rat numbers and damage are an increase in farmers’ net income through yield increase and a decrease in the use of chemicals. Pros and cons of these methods in different economic and cultural environments are discussed.

Chemical control is currently the primary driver of "Integrated Pest Management" (IPM) for rodents. This generally provides effective control in the short term, regardless of the rodent species. However, governments are concerned about the use of chemicals, especially when they are striving to provide clean and green food products for their domestic and export markets. In developing countries, the challenge is first to develop a good understanding of the ecology of the pest species and then assess the efficacy of using traditional and new methods of rodent control. This will enable adoption of management actions that are more environmentally sound and sustainable (environmentally and culturally). This approach is termed "Ecologically-Based Rodent Management" (EBRM). How EBRM operates in an operational sense is presented for two rather different geographic regions, research approaches and strategies for management. The first research approach is ecologically-based management of rodent pests in rice fields of Southeast Asia. As an indication of their impact, rodents are the greatest agricultural problem in Indonesia causing annual losses to rice production of 17%. I report on the development of a rodent management project in West Java, Indonesia. The initial phase of the research was developing an understanding of the population ecology and habitat use of the main pest species, the rice-field rat (Rattus argentiventer). These findings have been combined with local knowledge (of rodents and farming systems) to develop an ecologically-based management strategy of the rice-field rat at a village-level. The second research approach is biological control of house mouse populations in Australia. Mouse populations erupt into plague proportions in cereal-growing regions causing substantial economic and social stress to rural communities. We are examining whether mouse populations can be managed with fertility control either by a non-infectious agent delivered in an oral bait, or by infectious viruses as carriers of an infertility agent. Although the focus is often on the biotechnology aspect of this research, it is knowledge of the population ecology of mice and the epidemiology of mouse cytomegalovirus in field populations that will provide the critical context for this management strategy.

During 1995 to 1997, the efficacy of early tactical management of mouse populations in a project based on grain-growing farms in Victoria, Australia was examined. Farmers modified their management practices of crops (at sowing, harvest, and land preparation), and managed habitats on the boundary of cropped land (such as fencelines) and around farm buildings. One management practice examined was the effect on mouse populations of controlling weeds along margins of crops. On sites where farmers slashed or sprayed weeds in early spring, there was a comparative reduction in the abundance of mice in late summer compared to untreated sites.

This article provides an overview of the impact of rodents on agriculture, health, and biodiversity, with a particular focus on Africa. It acknowledges that while rodents make up a significant portion of mammalian species, only a small percentage of them have negative effects. The article highlights the 7th International Conference on Rodent Biology and Management, which concentrated on rodent biology and biodiversity in African highlands and mountains. It discusses the shift in focus from previous conferences, including increased research on fertility control of rodents and a greater emphasis on the One Health approach to rodent-borne diseases. The article covers various topics related to rodent biology and management, such as reducing flea and rodent populations simultaneously to prevent disease transmission and efforts in New Zealand to eradicate invasive rodents for the conservation of endemic wildlife. It also explores adaptations of rodent sensory systems, developments in rodent taxonomy, strategies for dealing with dietary toxins, and the use of African giant pouched rats for tasks like landmine detection and disease detection. The article underscores the importance of long-term population studies in understanding rodent populations and their impact on agriculture and human health. It concludes by acknowledging the contributions of researchers in the field and announcing the next International Conference on Rodent Biology and Management in 2025. [Extracted from the article]

Biological control using macro- or micro-parasites is a promising research area for control of rodents. The largest impediment to progress is a dearth of high quality research, under field conditions, on wild rodents and their diseases. A major challenge is to identify a candidate control agent which is sufficiently pathogenic, has a high transmission rate and is target specific. Once this has been done, ecological studies of both the host and the disease agent, and of the epidemiology of transmission, are required. Whether the desired pathogenicity is via increased mortality and/or reduced fertility will depend on the agent and on the dynamics of the pest species in particular agricultural systems. Overall, the best prospects for the biological control of rodents lies with agents that reduce fertility rather than increase mortality. The development of immuno-contraception using a virus as a vector is proffered as the most promising generic approach for the biological control of rodent pests.