The rice field rat, Rattus tanezumi, is the principal non-native rodent pest species reported in the Philippines. A medium-sized murid rodent with a tail that is longer than its head and body (Stuart 2004) is considered to cause serious damage to rice at both preand postharvest stages (Singleton 2003, Joshi et al 2000). In the Philippines, the use of synthetic rodenticides is the most common means of rat control. However, an ecologically based rodent management (EBRM) approach that uses a trap barrier system plus trap crop (TBS + TC) has recently been found to be widely successful on Asian rice farms (Singleton et al 2001). Effective management of R. argentiventer in Indonesia and Vietnam using TBS + TC relies on removing female rats from the population before the rice booting stage, before they are able to successfully raise the first litter of the year (Singleton et al 1999). This paper is the first report on the breeding dynamics of R. tanezumi caught in a TBS + TC.