New data on the introduction and dispersal process of small mammals in southwestern Europe during the Holocene: Castillejo del Bonete site (southeastern Spain)

In the Mediterranean realm, the development of navigation techniques by humans during the Mesolithic and the Neolithic favoured the dispersal of some small mammal species from Africa and the Levant into the European continent. Many details of this process still remain unclear such as the exact date of first arrivals of each species or how their dispersal into southwestern Europe occurred. In such a context, the new site of Castillejo del Bonete (southeastern Spain), provides exceptional information thanks to its rich microvertebrate assemblage. Over 8000 remains of small mammals have been identified in this site, belonging to eleven species. Radiocarbon dating performed directly on a specimen has given a date of 3819–3615 cal. BP. Thus, the small mammal assemblage of Castillejo del Bonete provides new evidence to reconstruct the biogeographical history of some small mammals of recent introduction in western Europe. The presence and relative abundance (12.45% of MNI) of the Western Mediterranean mouse (Mus spretus) is particularly interesting, since there are very few sites of this age in Iberia where its record can be considered reliable. A critical review of Mus species occurrences presented in this paper suggests that the Western Mediterranean mouse did not colonize southwest Europe before the Late Neolithic. Additionally, the absence of both the black rat (Rattus rattus) and the Etruscan shrew (Suncus etruscus) in this rich and diverse assemblage is in concordance with previous hypothesis which support the idea that the Iberian Peninsula was colonized by these two species on a more recent date