Conclusions
We here present a “snapshot” picture of the community structure of commensal small mammals captured in southern Senegal. This area corresponds to the current distribution area of R. rattus , a major invasive species well-established for more than one century in this part of Senegal (Konečný et al., 2013). Most of this area has apparently been colonized more recently by M. musculus , another major invasive rodent species with a rapid and ongoing invasion dynamics (Dalecky et al., 2015; Lippens et al., 2017). The contact between these invasive species and the native ones may therefore date from various periods according to the time of arrival / installation of R. rattus and M. musculus . This probably results in communities that cannot be considered at equilibrium in a number of cases, which in turn makes it difficult to envisage stabilized assembly rules in these species assemblages (see also Hima et al., 2019).
Nevertheless, the results obtained here, associated with others presented recently on each of these two invasive species in Senegal (e.g. in Lucaccioni et al., 2016; Stragier et al., 2020; Diagne et al., 2021) help to better understand their ecological characteristics and requirements, and to make some hypotheses on the evolution of the communities they constitute with their native counterparts in commensal contexts. Indeed, the invasive black rat and house mouse do not seem to have very specific habitat requirements, and they share similar niche breadth with native species in this respect. They also show important overlap in terms of room types they occupy, which should lead to frequent interactions. Other components of the ecological niche of these species should be considered, which may be more informative on the outcome of co-occurrence patterns and interspecific interactions. In these communities where the spatial range dynamics of the invasive species is rather well-known, a better knowledge of both niche characteristics and the nature of interactions between the species concerned will enable us to better understand co-occurrence patterns, and even to make some predictions on the temporal evolution of these patterns at different spatial scales (Bar-Masada et al,. 2015). At the local scale, fine-grained co-existence mechanisms would worth be studied in large cities showing both habitat complexity and a reasonable diversity of interacting species (such as Kédougou or Tambacounda). In addition to continuous spatio-temporal surveys over the studies areas to capture the changing dynamics within these small mammal communities, further multidisciplinary research efforts should be devoted to (i) unravel the multifactorial mechanisms underlying the (potential) changes observed in the community structure over time, (ii) depict the consequences of these modifications at ecological (e.g. species extirpation), social (e.g. threats to stored food) and/or health (e.g. emergence of rodent-borne zoonoses) levels, and (iii) move – by concerted efforts with local stakeholders and decision makers – from fundamental empirical results to sustainable and efficient management actions against the detrimental effects of some of these small mammals.