1. Dendrofoyrax brucei and Procavia johnstoni populations have been studied in kopjes surrounding the senior author's house.
2. The two species have been described and a short historical review of the Hyracoidea is given. Some notes are made concerning “Hyraceum”.
3. The kopjes under study are described, being typical of granite outcrops in the Serengeti region.
4. The adaptations of both species of hyrax for the kopje habitat are described. Observations are made on the diurnal activity patterns in relation to climatic conditions.
5. A list of all plants available to the animals is presented, and those eaten by either species are indicated. Comment is made on the lack of overlap in the diets of the two species, and this is suggested as being partly due to lack of pressure on food resources.
6. A discussion on the possible evolution of the kopje-dwelling habit is held, which concludes that reconvergence may have taken place as a result of forest giving way to woodland and plains.