Breeding ecology of the rice field rat (Rattus argentiventer Rob & Kloss, 1916) in irrigated rice ecosystem in Indonesia

Abstract

Rice field rat (Rattus argentiventer) as one of the most important pest is the main factor causing the largest yield loss and damage of Indonesian rice crops. The average of rice field damage reaches 161 000 ha, annually. Moreover, rats have also been known as a vector for some zoonoses in humans and infectious diseases in livestock. Most farmers usually practice inappropriate methods to reduce the impacts of the rice field rat attack and rely heavily on chemicals, causing risks to non-target species and the environment. The success of rat control is determined by a good understanding of its ecology. In lowland irrigated ecosystem, the rice field rat commences their breeding during the generative stage and terminate it at the early fallow season. The majority of male rats reach their sexual maturity at the booting stage whereas the females start to give birth at the early generative stage. They perform three times of birth with the average litter size is around 10 for every single rice cropping season. The highest number of embryos is observed at the first birth and getting lower at the second and the third pregnancy, respectively. Most females in the field give birth twice and only a few of them indicate three times of pregnancy. The major factor triggering an increase of rice field rat population density is the availability of food, which lead to the commencement of breeding and subsequent births occur in the generative stage. There is also some ratoon growing during the fallow period which has extended the rat breeding period and affected the population increase.