Variability of Grassland Forage Resources and Their Division by a Complex of Herbivorous Mammals in the Case of Joint Grazing

A negative dependence of the digestibility of grassland vegetation on the amount of grasses in the feed consumed, which is in turn associated with an increased content of silicon compounds in grasses, is found. Using the example of four species of herbivores (Przewalski’s horse, American bison, Bactrian camel, and saiga), which differ in the specifics of digestion, the selectivity of their nutrition was studied in relation to two groups of plants differing in digestibility—grasses and forbs. Saigas, like other obviously highly selective consumers of easily digestible food, strictly select forbs with a low silicon content and high digestibility. With the dominance of low-digestible grasses on the grassland and their forced consumption, the saiga population is not viable. Horses and bison, like other representatives of equines and large ruminants, due to the characteristics of the digestive system, are able to assimilate low-digestible grass feeds successfully and are highly specialized in feeding on grasses. The exclusion of forbs from the diet of horses and bison is associated with the increased toxicity of this group of plants. Camels do not discriminate in the choice of grasses and forbs of different nutritional value and currently actively use fallow areas (on former arable land) dominated by weedy plants, which are avoided by other herbivores. Different specialization in the choice of forage plants when different species of animals graze together causes their division in the use of grassland feed resources, eliminates competition between them, and acts as a necessary factor in preserving the species diversity of grassland vegetation.