Based on compiled small mammal trapping data collected over 12 years from Benin and Niger (3701 individual records from 66 sampling sites), located in mainland Africa, we here describe the small mammal community assemblage in urban habitats along the commercial axis connecting the two countries, from the seaport of Cotonou to the Sahelian hinterland, with a particular focus on invasive species. In doing so, we document extant species distributions, which highlight the risks of continuing the range expansion of three synanthropic invasive rodent species, namely black rats (Rattus rattus), brown rats (R. norvegicus), and house mice (Mus musculus). Using various diversity estimates and community ecology approaches, we detect a latitudinal gradient of species richness that significantly decreased Northward. We show that shrews (Crocidura) represent a very important component of micro-mammal fauna in West African towns and villages, especially at lower latitudes. We also demonstrate that invasive and native synanthropic rodents do not distribute randomly in West Africa, which suggests that invasive species dynamics and history differ markedly, and that they involve gradual, as well as human-mediated, long distance dispersal. Patterns of segregation are also observed between native Mastomys natalensis and invasive rats R. rattus and R. norvegicus, suggesting potential native-to-invasive species turn over. Consequences of such processes, especially in terms of public health, are discussed.

Black rat (Rattus rattus), brown rat (Rattus norvegicus), and house mouse (Mus musculus) are known to be among the most common anthropophilic rodent species in cities worldwide. These species are responsible for the destruction of domestic and industrial materials, considerable damage to food stocks as well as zoonotic pathogens circulation and transmission to humans and animals. These invasive species have disseminated in all continents following human-mediated exchanges, especially maritime transports. In particular, seaports appear as privileged rats and mice’s entry points into new regions, thus making them international regulations’ priorities for rodent surveillance and management. Yet, studies on seaport rodents are rare; in particular, investigations on their genetic structure are almost inexistent, thus precluding science-guided interventions. In order to fill such a gap, our study focused on the population genetics of R. rattus, R. norvegicus and M. musculus in the Autonomous Port of Cotonou, Benin. Nine different sites were surveyed for three years. In total, 366 R. rattus, 188 R. norvegicus and 244 M. musculus were genotyped using 18 microsatellites, 16 microsatellites and 17 microsatellites, respectively. Our results show very well-structured genetic clusters in all three species as well as limited impacts of rodent control campaigns. Using comparisons with genotypes from other European, Asian and African countries, we suggest for the first time that settlement of newly introduced individuals may be a rare event. Implications in terms of management units and control and monitoring are discussed.

The prevalent use of synthetic chemical rodenticides (both 1st or 2nd generation anticoagulants and acute rodenticides) is the primary method for managing rodents in sub-Saharan Africa. However, this practice poses substantial health and environmental risks and often fails to yield significant, sustainable reductions in rodent pest populations. In this paper, the second one of a two-part series, we advocate for a more responsible and sustainable approach to rodent management in urban and agricultural settings in sub-Saharan Africa. We propose a shift towards environmentally friendly rodent management strategies, specifically emphasizing the adoption of Ecologically-Based Rodent Management (EBRM) as a viable alternative to synthetic chemical rodenticides. EBRM relies on a comprehensive understanding of pest rodent biology, ecology, and behavior, along with the implementation of a range of community-based interventions. These actions are designed to ensure the consistent reduction of rodent pest populations to economically and hygienically acceptable levels. By embracing EBRM, we not only anticipate a reduction in the social impacts of pest rodents in a cost-effective manner but also a significant decrease in the risks posed by rodents and synthetic chemical rodenticides to human health and the environment. This paradigm shift towards EBRM promises a more sustainable and responsible approach to rodent management in sub-Saharan Africa.