Subgenus Mus. See J. T. Marshall, Jr. (1998) for identification of synonyms. Throughout its range, M. spretus is sympatric but not syntopic with M. musculus domesticus (Boursot et al., 1993; Mitchell-Jones et al., 1999). The species has been the subject of various inquiries covering biometrical and morphological analyses (Darviche and Orsini, 1982; Engels, 1980, 1983b; Gerasimov et al., 1990; Palomo, 1988; Palomo et al., 1983; Vargas, et al., 1984); chromosomal and electrophoretic studies (Cano et al., 1984; Engels, 1983a; Matsuda and Chapman, 1992; Traut et al., 1992); distribution of the p53 pseudogene as another molecular trait distinguishing M. spretus from M. spicilegus and M. musculus (Ohtsuka et al., 1996); phylogenetic analysis of mitochondrial D-loop sequences to also distinguish M. spretus from M. spicilegus and M. musculus (Flegr et al., 1994); variability in mtDNA that revealed two genetically distinct phylogenetic groups within M. spretus (Boursot, et al., 1985); contrasts between M. spretus and M. musculus (domesticus) using DNA sequence of LINE-1 elements (Casavant and Hardies, 1994); phylogenetic relationships assessed by sequences from several different genes that placed M. spretus in a clade with M. musculus, M. macedonicus, and M. spicilegus (Graur, 1994; Larizza et al., 2002; Lundrigan et al., 2002; Martin et al., 2000; Prager et al., 1996, 1998); combined analyses of morphological traits, DNA/DNA hybridization, and mitochondrial 12S rRNA sequences join M. spretus with M. spicilegus, M. macedonicus, and M. musculus in a clade separate from an Asian clade composed of M. caroli, M. cervicolor, and M. cooki (Auffray et al., 2003; Chevret et al., 2003); and differences between M. spretus and M. musculus in thermoregulatory capabilities (Gorecki et al., 1990). Evidence indicates that M. spretus forms a sister group to M. spicilegus, M. macedonicus, and all taxa embraced by Mus musculus (Prager et al., 1998). Alcover et al. (1985) described parvus as a subspecies of M. spretus. European population reviewed by Mitchell-Jones et al. (1999), Balearic Isls by Alcover et al. (1985) and Alcover and Gosalbez (1988), and Moroccan by Aulagnier and Thevenot (1986). Relationship between habitats and abundance in Algeria reported by Khidas et al. (2002). Torre et al. (1996) analyzed population in NE Spain by studying owl pellet remains.

Mus spretus has been identified from middle Pleistocene beds at Jebel Irhoud in Morocco (Amani and Geraads, 1993), from late Pleistocene in the N Rif Mtns of N Morocco (Ouahbi et al., 2001), and Pleistocene sediments of Tunisia (Mein and Pickford, 1992). Dobson (1998, 2000) postulated that the species is native to the Maghreb of North Africa and may have been transported by humans, presumably inadvertently, to SW Europe, which J. T. Marshal, Jr. (in litt., 2004) finds unlikely because M. spretus is found only in "wild" outdoor habitats.