 In 1974 Klein studied the fossils of Hippotragus species in South Africa. Most of these were found to represent the bluebuck and the roan antelope. The fossil record suggested that the bluebuck occurred in large numbers during the last glacial period (nearly 0.1 million years ago), and was more common than sympatric antelopes. The bluebuck could adapt to more open habitats than could the roan antelope, a notable point of difference between these species. Fossils of the bluebuck have been found in the Klaises River and the Nelson Bay Caves (near Plettenberg Bay) and Swartklip (to the west of the Hottentots Holland mountains). The aforementioned 2013 study noted that the western and southern CFR were separated by biogeographical barriers, such as the Cape Fold Belt and afromontane forests. A 2011 study suggested that low sea levels facilitated migrations for large mammals; therefore the rise in sea levels with the beginning of the Holocene would have led to fragmented bluebuck populations and distanced many populations from the western coast (fossils dating to this period are scarce in the western coast but have been recorded from the southern coast). Thus, a mass extinction could have taken place, leaving behind mainly the populations that remained in the resource-rich western CFR. The causes of the drastic decline in bluebuck populations just before the 15th and 16th centuries have not been investigated; competition with livestock and habitat deterioration could have been major factors in its depletion.
