The ecological separation of 14 common ungulate species living in close contact with each other in a Tanganyika game reserve is shown to be achieved by six different factors:
1. the occupation of different vegetation types and broad habitats;
2. the selection of different types of food;
3. the occupation of different areas at the same season;
4. the occupation of the same area at different seasons;
5. the use of different feeding levels in the vegetation;
6. the occupation of different dry season refuges in the Masai area when the competition for food is greatest (zebra and wildebeest).
Habitat preferences are indicated by the frequency distribution of each species along the central of three 8,000 yard parallel transect paths which were traversed nearly daily for four years. Characteristic patterns of frequency are apparent for each of the species in the vegetation zones represented in the transect area. Certain species show a tendency, sometimes strong, to concentrate along the boundaries between adjoining vegetation zones and in the ecotones between the zones. This is ascribed to a greater diversity of food, availability of shelter from the sun and/or greater protection from predators.
Records of the animal species eating particular plant species are shown and (qualified in the light of other observations) used to deduce food preferences. The species are classified broadly into grass-eaters, browsers and mixed feeders (grass and browse). In the case of the three common grass-eaters, buffalo, wildebeest and zebra, a percentage analysis of the grass species eaten indicates that little differential preference is shown but that they take the palatable grasses largely in proportion to the frequency in which they occur in the habitats most used by the ungulate concerned. Buffalo are separated by their preference for denser vegetation. Wildebeest and zebra largely overlap ecologically in all respects except that the bulk of the populations of each species move to different dry season areas. Those species which are able to live without drinking free water, notably impala and Grant's gazelle, are able to make use of wild areas of waterless country when the animals requiring water are forced to move into dry season concentration areas near water.
The influence of the animals on the habitats and on other species is discussed and instances are given of species helping to shape the habitat to the advantage of both themselves and other species. Elephants are the main habitat modifiers and their capacity to improve water supplies and change the vegetation, and their facilitation of the feeding of other species is described. The formation of mixed herds is interpreted as being protective to one or both species concerned and is a further important facilitation. Little or no hindrance of one ungulate species by another was seen although herbivores show antagonistic behaviour towards carnivores smaller than themselves.