why does the presence of 22 large herbivore species at Mpala seem to contradict the competitive exclusion principle Dr. Pringle described in his introduction?

Dr. Pringle suggests that there's only very few large herbivorous species that can survive in certain area. The reason behind his claim is that according to him there will be only enough food for few large species, so there's natural limitations in the food sources, as there should be enough to support them in order for them to survive.

On the other hand, in Mpala, there's 22 large herbivorous species, which directly contradicts Dr. Pringle's hypothesis. The reason why so many large species of herbivores an survive in Mpala and always have enough food for all of them, is that they have all specialized in eating certain types of plants or parts of plants, thus they are not direct competition to one another, and there's always enough food for all of them.