## 2 Materials and Methods  
Skulls and mandibles morphologically ascribable to the _Microtus savii_ group were retrieved from Barn owl (_Tyto alba_ [PERSON] 1769), Little owl (_Atiene notcua_ [PERSON] 1769), Long-eared owl (_Asio otus_ [PERSON] 1758) (Figure 1) and Common kestrel (_Falco intinunculus_ [PERSON] 1758) pellets collected in different locations selected for morphological analysis. Bones found in pellets from all the raptor species were used for morphometrical analyses, whereas a subsample of bones found in pellets from _A. otus_ was used for genetic analysis of a specific population. For the odontometric analysis, a total of 455 first lower molars (both right and left) belonging to 3 geographical populations sampled across the Umbria region (Figure 2) were analysed. Six measurements, v3, v4, v6, v18, v20 and v21 (Figure 3A), were taken on the occlusal surface of m1 [19; 23; 24] using a Nikon Measuring Microscope MM-60 (precision 1 \(\mu\)m) [25]. Three indexes were calculated: the development of the anterior part of m\({}_{1}\) [AP = (v6 - v3)/v6 \(*\) 100], the tilt of the pitymyan rhombus (PR = v4 - v3) and the closure of the anterior loop (AL = (v20 - v18)/v21 \(*\) 100). Four criteria were analysed by means of a PCA analysis combined with a multivariate analysis of variance (MANOVA) and one-way analysis of variance (ANOVA) completed by a Bonferroni's test when necessary (ANOVA \(p\) < 0.05): total length of m\({}_{1}\) (TL), the development of the anterior part (AP), the tilt of the pitymyan rhombus (PR) and the closure of the anterior loop (AL) (Figure 3B). For the palatilar length analysis (Figure 3C) a subsample of 41 specimens retrieved between 2011 and 2012 under an _A. otus_ roost from Montefalco was analysed. The comparison of the palatilar length between anterior loop groups (open AL vs closed AL) was performed using the Wilcoxon-Mann-Whitney test. In that subsample, 12 specimens presented an m\({}_{1}\) with a closed anterior loop (\(\leq\)20%), 10 specimens presented an m\({}_{1}\) with a moderately closed anterior loop ([20; 25] %), 8 specimens presented an m\({}_{1}\) with a moderately open anterior loop ([25; 30] %) and 11 specimens presented an m\({}_{1}\) with an open anterior loop (\(\geq\)30%). Within the subsample, 33 specimens (Figure 4) were destined for mtDNA analysis in order to see if specimens with open anterior loops of m\({}_{1}\) belonged to _M. brachycerus_. Figure 1: (**A**) Entire Long-eared owl pellet sampled under the Montefalco roost; (**B**) bones of at least two prey items retrieved from pellets (scale bar is 2 cm). Figure 3: (**A**) Measurements taken on the occlusal surface of the first lower molar in the studied specimens. (**B**) First lower molars of _Microtus (Terricola)_ with open (**left**) and closed (**right**) anterior loops. (**C**) Measurement of the palatilar length in _Microtus (Terricola)_ skull (redrawn from [6]). Figure 2: (**A**) Presumptive distribution of _Microtus savii_ (orange), _M. brachycercus_ (gray) and _M. nephdensis_ (green) (redrawn from [2]). (**B**) Map of the municipalities of the Umbria region. _Microtus_ sp. Geographical populations are shown with different colours: red (Montefalco), light blue (Trevi), and green (North and Central provinces of Perugia). Statistical analyses and graphical elaborations were carried out with the R statistical framework (cran.r-project.org) (accessed on 14 March 2023) within the RStudio Development Environment (rstudio.com) (accessed on 14 March 2023). To rule out contamination from operator DNA, all laboratory procedures were carried out under a laminar flow hood using disposable nitrile gloves, disposable FFP-2 face masks and proceeding with frequent and thorough cleaning of all possible surfaces with denaturized ethyl alcohol. To prevent cross-contamination, all samples were handled individually with researchers cleaning the workspace before and after each processed sample. To prevent the genotyping of the same individual, only the left hemimandible from each skull was selected for DNA extraction.