The impact of imposed female sterility on field populations of ricefield rats (Rattus argentiventer)

A decrease in the reproductive rate of a pest population may lead to a decrease in population growth and in the associated damage to agricultural crops. In this study, a single-dose anti-fertility treatment was simulated through surgical and hormonally based sterilisation of female ricefield rats, Rattus argentiventer, in a rice-based agro-ecosystem. Up to 76% of adult females were sterilised on 10 ha plots before the start of the breeding season in two populations for each treatment (surgical or hormonally based sterilisation). There were two untreated populations. None of the treatments led to a decrease in population growth, breeding performance or crop damage nor was there an increase in rice yield. The treatments did not result in numeric or reproductive compensation at the rat population level. It is likely that immigration by fertile female rats outweighed the potential effects of sterilised females at the population level. The findings highlight the importance to test whether anti-fertility treatments on a larger scale than in this study and multiple-dose treatments can effectively reduce the population size of ricefield rats. © 2006 Elsevier B.V. All rights reserved.