Résumé
International trade has been favoring the dissemination of a wide panel of
invasive alien species. Upstream prevention through the monitoring of
entry points is identified as an appropriate strategy to achieve control
of bioinvasions and their consequences. Maritime transports have been
responsible for the introduction worldwide of exotic rodents that are
major pests for crops and food stocks as well as reservoirs of many
zoonotic pathogens. In order to limit further dissemination, the
International Health Regulation constrains decision makers and
socio-economic stakeholders to manage ship-mediated import/export of
rodents within seaports. Unfortunately, eco-evolutionary insights into
rodent introduction events that could guide preventive actions in seaports
are very scarce. In order to bridge this gap, we here describe the results
of a three-year-long survey of small mammals conducted in the Port of
Cotonou, Benin, that aims at assessing the spatio-temporal distribution,
diversity and relative abundance of invasive and native rodents. 960 small
mammal individuals were captured in nine within-seaport sites. We found
(i) a marked predominance of invasive species (84% of the individuals
belonging to Mus musculus, Rattus rattus, R. norvegicus), (ii) with native
species (i.e., Mastomys natalensis and the shrew Crocidura olivieri)
essentially restricted to peripheral non-industrial areas, as well as
(iii) a fine-scale spatial segregation stable over time between the
invasive Norway rats and house mice on the one hand, and the black rats
and shrews on the other hand. Furthermore, trapping before and after two
successive rodent anticoagulant-based control campaigns indicates that
they were poorly efficient and that subsequent rodent recolonization
occurs 6–12 months following intervention. Synthesis and applications: Our
results are discussed in terms of ecological processes at play (e.g.,
interspecific interactions) and operational actions that may be
implemented to improve rodent control (e.g., assessment of proper
eradication units, environmental modifications) and to limit
re-infestation (e.g., rat-proofing of moors and buildings).