occurred throughout the Rift Valley, and its range extended eastward into northwestern Somalia. It has disappeared from Somalia by 1930. Its populations are very low and on the decline. A. b. tora Gray, 1873 : Known as the tora hartebeest. Formerly occurred in northwestern Ethiopia and western and southwestern Eritrea. Its present status is unclear, though locals have reported small numbers from these areas. Genetics and hybrids In 2000, a study scrutinised two major populations of the Swayne's hartebeest, from the Senkele Wildlife Sanctuary and the Nechisar National Park, for mitochondrial (D-loop) and nuclear (microsatellite) variability in an attempt to estimate the levels of genetic variation between the populations and within the subspecies. The results showed a remarkable differentiation between the two populations; that from the Senkele Wildlife Sanctuary showed more genetic diversity than the one from the Nechisar National Park. Another revelation was that the translocation of the individuals from the Senkele Wildlife Sanctuary in 1974 had not made a significant contribution to the gene pool of the Nechisar National Park. Additionally, the Swayne hartebeest populations were compared with a large red hartebeest population, and both subspecies were found to have a high degree of genetic variation. The study advocated in situ conservation of the Swayne's hartebeest and a renewed attempt at its translocation in order to conserve genetic diversity and increase its population in both the protected areas. The diploid number of chromosomes in the hartebeest is 40. Hybrids are usually reported from areas where ranges of two subspecies overlap. Hybrids between the Lelwel and Tora hartebeest have been reported in eastern Sudan and western Ethiopia, in a stretch southward from the Blue Nile to about 9° N latitude. A study proved a male hybrid of the red hartebeest and the blesbok (Damaliscus pygargus) to be sterile. Sterility of the hybrid was attributed to difficulties in segregation during meiosis, indicated by azoospermia and a low number of germ cells in its seminiferous tubules. There are three well-defined hybrids between the subspecies: Alcelaphus lelwel x cokii: Known as the Kenya Highland hartebeest or the Laikipia hartebeest. It is a cross between the Lelwel and Coke's hartebeest. This hybrid is lighter in colour and larger than Coke's hartebeest. It is a light buff with reddish-tawny upper parts, and the head is longer than in Coke's hartebeest. Both sexes have horns, which are heavier as well as longer than those of