Characterized by 2n = 32, FNa = 52-54 (Britton-Davidian et al., 1995; Green et al., 1980; Volobouev et al., 2002b) and a distinctive hemoglobin electromorph (Green et al., 1980; Robbins et al. 1983). Samples with these chromosomal features have also been found in Senegal (Duplantier et al., 1990a, b; Granjon et al., 1996); Côte d’Ivoire, Central African Republic, Republic of Congo, and Chad (Matthey, 1955, 1966a, b); Sierra Leone and Burundi (Robbins et al., 1983); S Benin (Codjia et al., 1996); Burkina Faso, Mali, Niger, and Nigeria (Granjon et al., 1997b; Hubert et al., 1983); Somalia (Capanna et al., 1982); Ethiopia (Baskevich and Orlov, 1993; Lavrenchenko et al., 1998a); Tanzania (Fadda et al., 2001; Leirs, 1992; Leirs et al., 1989, 1993); Zimbabwe (Lyons et al., 1980); Namibia (Hallett, 1979), and South Africa (Granjon et al., 1996; Green et al., 1980;). Using chromosomal data, laboratory crosses, and principal component analysis of cranial and dental measurements, Granjon et al. (1996) demonstrated that samples of M. natalensis from South Africa were conspecific with those obtained from Senegal. Musser and Carleton (1993) had speculated that M. natalensis "probably occurs in Angola, S Zaire [Dem. Rep. Congo], Zambia, Malawi, Mozambique, and farther north in Tanzania and perhaps may even range more extensively in West Africa, but at this time samples from those regions have not been identified by linking chromosomal and biochemical data to morphology. Realizing this problem, some regional faunal accounts provisionally list specimens under M. natalensis (e.g., Ansell and Dowsett, 1988, for Malawi mammals)." Data now available indicate that the species occurs throughout subsaharan Africa (except SE southern Africa; Granjon et al., 1997b; Skinner and Smithers, 1990), and may be "the most widely distributed mammal of Africa." (Granjon et al., 1997b).

The following studies focus on systematics and distribution of M. natalensis: reproductive distinctions among M. natalensis, M. erythroleucus, and M. huberti in Senegal (Duplantier et al., 1996); chromosomal contrasts between M. natalensis and M. erythroleucus from S Benin (Codjia et al., 1996); phylogenetic analysis of chromosomal data that indicated closer relationship between M. natalensis and M. huberti than with M. coucha and M. erythroleucus (Britton-Davidian et al., 1995); data on trapping and recover from owl pellets in N Malawi (Denys et al., 1999), and regarded as the most common species trapped in S Mali (Meinig, 2000); distribution in the Eastern Arc Mtns and Gonja Forest Reserve of Tanzania (Stanley et al., 1998, 2002); and occurrence in the Bazaruto Arch. off the coast of S Mozambique (Downs and Wirminghaus, 1997). Population in KwaZulu-Natal Province of South Africa extensively discussed by Taylor (1998), and that in Southern African subregion reviewed by de Graaff (1997q). See account of M. coucha for contrasts with that southern African species.

Synonyms based on South Africa samples are those listed by Meester et al. (1986). All other synonyms refer to samples described from Angola, Uganda, Kenya, and Tanzania (see G. M. Allen, 1939, and Crawford-Cabral, 1998), regions where other species closely related to M. natalensis (M. coucha, M. huberti, and M. erythroleucus) are not presently known to occur. Holotypes that are the basis for most of these names have been identified as examples of Mastomys by Van der Straeten and Robbins (1997) but were not allocated to species. Eventually, our allocations will have to be verified by a systematic revision of M. natalensis that includes accurate identification of holotypes. The identity of longicaudatus, originally described as a species of Mystromys, was first documented by Misonne (1966). Other possible synonyms are listed in account of M. erythroleucus. The taxon fumatus has traditionally been regarded as a species of Myomys (see Musser and Carleton, 1993), but the holotype is a young example of Mastomys (Van der Straeten and Robbins, 1997; Musser’s examination of holotype); see account of Myomyscus brockmani.

Tanzanian populations of M. natalensis have been the focus of a three-year study by Leirs (1992) and Leirs et al. (1990, 1993, 1996) resulting in exhaustive information on various aspects of population ecology. Based upon their morphometric and chromosomal study of 6083 specimens from localities throughout Tanzania, they concluded M. natalensis–not M. coucha, M. huberti, or M. erythroleucus- is the most common species and that seasonal variation in cranial dimensions within populations is greater than geographic variation among them.