Rating the rat: global patterns and research priorities in impacts and management of rodent pests

We report the results of the first systematic assessment of global patterns and research priorities emerging in the field of rodent pest management. We carried out an extensive literature review targeted towards identifying the most relevant rodent pests, their impacts and the most common methods used to control them. We identified three disproportionally important pest species that are characterized by severe, generalist and geographically widespread impacts: the black rat Rattus rattus, the Norway rat Rattus norvegicus and the house mouse Mus musculus. Overall, only 7% of known rodent species may be considered pests. Scansorial (i.e. terrestrial and semi-arboreal) and fossorial species are generally important as pests, while aquatic and arboreal species have only specific impacts. Impacts of rodent pests on arable crops were studied most, followed by impacts on ecosystems. Studies on arable crops were typical in countries with low net income and health expenditure, while the opposite was observed for studies on ecosystems. Poisons were the most commonly used control method, followed by traps and habitat management. The need to control rodent species is expanding, especially to protect ecosystems and public health. Unlike in other fields of pest management (e.g. insect control), in rodent control we are approaching new problems with old solutions; control strategies and methods have not kept pace with emerging impacts. The need to control a rodent pest species is higher when it is non-native than within its original geographical range. The impact of a rodent species in its native range is a good predictor of the impact it may have in areas of introduction. Our review will contribute towards guiding researchers and stakeholders to focus research efforts and investments on a subset of species, and on new, less hazardous control techniques.