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.