Are rodent population eruptions in southeast Asia associated with quantity or quality of food?

Rice field rat’s population occasionally undergoes widespread eruption in Indonesia, Vietnam, the Philippines, and Myanmar following extreme weather event. Asynchronous or aseasonal planting of crops in response to unusual weather events can extend the period that high quality food is available to rodents. Consequently, rodents may extend their breeding season and a population eruption is more likely to occur. However, it is unclear the association between the quality and quantity of food and the reproductive success of female rice field rats. An improved understanding of the effects of food availability and quality on rodent reproduction could enable better forecasts of rodent outbreaks in response to unusual weather events which could lead to asynchronous or aseasonal planting of crops. We studied how the breeding performance of the rice field rat, Rattus argentiventer, responded to food supply at different stages of the rice crop in the Philippines. Our results suggest that rice plants at the booting to ripening stages provided high quality food for rice field rats and it drove higher conception rate of female rats at these stages of the rice crop. We contend that the extension of the growing season by 3 to 4 weeks provides high quality food for rodents for an extended period, which in turn provides sufficient conditions for a population eruption. Therefore we recommend that synchronous planting is the effective proactive action for rodent management