One or different niches are occupied by herbivores in the African savannah?

In the savannah, animals occupy different ecological niches. An ecological niche is a place occupied by a species in a biocenosis, including a complex of its biocenotic connections and requirements for environmental factors. The term was introduced in 1914 by J. Grinnell and in 1927 by Charles Elton.
The ecological niche is the sum of the factors of the existence of this species, the main of which is its place in the food chain.
Ecological niche may be:
fundamental – determined by a combination of conditions and resources, allowing the species to maintain a viable population;
implemented – the properties of which are due to competing species.
This distinction emphasizes that interspecific competition leads to a decrease in fertility and viability, and that there may be such a part in the fundamental ecological niche that the species occupying as a result of interspecific competition are no longer able to live and successfully reproduce.
The ecological niche cannot be empty. If a niche becomes empty as a result of the extinction of a species, then it is immediately filled with another species.
The habitat usually consists of separate areas (“spots”) with favorable and unfavorable conditions; these spots are often only available temporarily, and they arise unpredictably both in time and in space.
Free sites or “gaps” in habitats occur unpredictably in many biotopes. Fires or landslides can lead to wasteland formation in forests; a storm can expose an open section of the seashore, and gluttonous predators anywhere can exterminate potential victims. These vacant sites are invariably populated again. However, the very first settlers will not necessarily be those species that for a long time are able to successfully compete with other species and displace them. Therefore, the coexistence of transient and competitive species is possible for as long as unpopulated areas appear with a suitable frequency. The transient species is usually the first to populate a free site, master it and multiply. A more competitive species populates these areas slowly, but if the settlement has begun, then over time it wins the transient species and multiplies.
The doctrine of ecological niches is of great practical importance. When introducing foreign species into the local flora and fauna, it is necessary to find out what ecological niche they occupy at home, whether they will have competitors in the places of introduction. The wide distribution of muskrat in Europe and Asia is explained precisely by the absence in these regions of rodents with a similar lifestyle.
In related species living together, there is a very subtle distinction between ecological niches. For example, ungulates grazing in the African savannah use grazing food in different ways: zebras mostly pick grass tops, wildebeests feed on zebras, gazelles pluck the lowest grasses, and swamp antelopes are content with dry stalks left after other herbivores. Due to the separation of niches, the total bio-productivity of such a herd with a complex species composition is growing. The peasant herd, consisting of cows, sheep, goats, is much more efficient, from an environmental point of view, uses meadows and pastures than a single-herd, monoculture is the least effective way of farming.