Mammals were collected and observed on seven jebels in the Sudan. A brief description of the position and geology, size, amount of soil, vegetation and rainfall is given for each jebel since these features are important in determining the variety and abundance of the mammalian fauna.
There are few mammalian species, if any, on the desert jebels. Acomys cahirinus is the commonest mammal on these jebels, and it may be very abundant if the jebel is large enough. Small desert jebels appear to have no mammals.
The jebels covered with trees and grass in the woodland savanna region have many species, although their densities are not as high as on the desert jebels. Larger size, dense vegetation cover, and many habitats may be responsible for this greater diversity (e.g. there are 34 recorded species, except bats, on Jebel Marra).
In the desert, the “jebel” and the “desert” faunas are distinct, whereas in the woodland savanna there is an overlap between the mammals of the jebel and those of the savanna. The desert jebels are now “islands”, so each population is isolated from the next. This situation is probably due to the past climatic and vegetational history of the region. In the woodland savanna, jebel populations are continuous with those of the savanna.
All the populations of Acomys in the study area appear to belong to one subspecies, Acomys cahirinus cineraceus. The specimens from the north were the palest, and those from the south were the darkest. Probably all Acomys in this region belong to the same species which forms a cline showing great variation dependent on climate and topography.