The abundance and microhabitat use of rodents were investigated in four different habitats: two rain-fed crop fields with differing stone bund density, an irrigated field and bushland. A total of 444 individual small mammals belonging to six rodent and one shrew species were recorded in trapping grids and line transects. Of these, 230 individuals (52%) belonged to three pest rodent species of crop fields in northern Ethiopia: Stenocephalemys albipes (65%), Mastomys awashensis (25%) and Arvicanthis niloticus (10%). Population abundance of the three species was higher in the early dry season compared to the rainy season. While the bushland was significantly (p < 0.05) favoured by S. albipes and M. awashensis in both seasons, the irrigated field was preferred by Arvicanthis niloticus in the early dry season. In the early dry season, the microhabitat use of A. niloticus was strongly associated with the type of ground cover (herb) (R2adj = 0.152, P < 0.01). While M. awashensis was associated with vegetation density (R2adj = 0.13, P < 0.01), S. albipes was associated with vegetation cover (R2adj = 0.102, P < 0.001). The findings indicate that co-occurring pest rodent species prefer different microhabitats. Understanding their co-occurrence particularly in crop fields is vital for crop protection as they are known serious agricultural pests in northern Ethiopia.

In 2012, Tigray orthohantavirus was discovered in Ethiopia, but its seasonal infection in small mammals, and whether it poses a risk to humans was unknown. The occurrence of small mammals, rodents and shrews, in human inhabitations in northern Ethiopia is affected by season and presence of stone bunds. We sampled small mammals in two seasons from low- and high-density stone bund fields adjacent to houses and community-protected semi-natural habitats in Atsbi and Hagere Selam, where Tigray orthohantavirus was first discovered. We collected blood samples from both small mammals and residents using filter paper. The presence of orthohantavirus-reactive antibodies in blood was then analyzed using immunofluorescence assay (human samples) and enzyme linked immunosorbent assays (small mammal samples) with Puumala orthohantavirus as antigen. Viral RNA was detected by RT-PCR using small mammal blood samples. Total orthohantavirus prevalence (antibodies or virus RNA) in the small mammals was 3.37%. The positive animals were three Stenocephalemys albipes rats (prevalence in this species = 13.04%). The low prevalence made it impossible to determine whether season and stone bunds were associated with orthohantavirus prevalence in the small mammals. In humans, we report the first detection of orthohantavirus-reactive IgG antibodies in Ethiopia (seroprevalence = 5.26%). S. albipes lives in close proximity to humans, likely increasing the risk of zoonotic transmission.

Despite its biogeographical uniqueness, where two vast savanna regions are separated by the Afromontane mosaic vegetation, there is a significant lack of small mammal sampling in the Tigray region of Ethiopia. Leveraging all our available data on rodents and shrews in the region, we tested the hypothesis that the Afromontane mosaic vegetation in the highlands acts as a barrier to gene flow between taxa found in the Somali-Masai and Sudanian savanna in the southeast and western lowland parts of the region, respectively. Morphological and DNA sequence analysis confirmed the presence of 23 species of small rodents and shrews in the region. We recorded 18 of these species in the Afromontane mosaic vegetation, seven species in the Sudanian savanna, and four species in the Somali-Masai savanna. Notably, the fauna of Sudanian savanna was strikingly different from that of the Somali-Masai savanna at both intraspecific and interspecific level, suggesting northern Ethiopian highlands as very strong biogeographic barrier for taxa adapted to arid lowlands. However, the reported species diversity remains provisional, and additional sampling from unexplored areas is needed. Furthermore, some of the reported taxa, in this study, such as Mus cf. tenellus, Crocidura cf. fuscomurina, Dendromus sp. indet. 2, and Otomys cf. cheesmani, require detailed taxonomic investigation and may represent new species. A robust understanding of the taxonomic diversity and distribution of the small mammals in the region is crucial for effective conservation planning as well as for addressing practical questions related to rodents, such as in public health and pest management.