Small vertebrates, thanks to their abundance and diversity in archaeological sites, provide a significant amount of data on the palaeoenvironmental and taphonomic context of human occupations. Moreover, the fact that they are highly habitat-dependent allows for fine palaeoenvironmental reconstructions on a local scale. It is indeed to be considered that the local environment have a direct impact on the human groups, their subsistence strategies, land use, etc. In Europe, the strong climatic variations taking place during the Late Pleistocene mark the last occupations of Neanderthal in western Europe. Following the last interglacial phase of the Eemian (MIS 5e), a climatic deterioration took place. These climatic changes had a significant impact on Neanderthal populations in Europe, their environment, and the distribution of their resources. Until now, few MIS 5 sites have yielded faunal remains, especially microfaunas, in northwestern Europe. However, recently excavated sites have yielded significant bone accumulations thanks to an exceptional depositional and preservation context. This is notably the case of four sites located in the northern half of France: Caours, Waziers, Mutzig and le Rozel. These sites allow us to apply two methods to reconstruct climatic parameters, the “bioclimatic model” and the “applied ecology” methods, which allow us to obtain notably the mean annual temperature and the summer/winter gap. The estimated temperatures correspond to a temperate environment although local specificities are present. Biodiversity is quite low, especially in the Eemian sites. This decrease in biodiversity during global warming does not correspond to what is observed in southern Europe, where palaeo-communities are well documented and where there is no significant decline in species diversity. There could therefore be a very different response to the phases of global warming between animal communities in southern and northern Europe, but more data on this latter are still required.