The succession of ungulate fauna was studied under conditions of artificially high density and limited residential area on the Biryuchy Island of the Azov-Sivash National Nature Park. Forming of inter-specific relationships between populations of the moufflon, red-deer and fallow-deer were revealed. The social hierarchy of the mentioned species, which are at the same trophic level, is determined. For the population of each species the factors influencing the dynamics of its number are given. Competition of species in steppe habitat is based solely on trophic relationships because the protective properties of the land are minimized. The forage base creates equal conditions for different species, since there is no woody vegetation in the steppe, which makes the large size of the red deer not important for the food obtaining. Concerning the fallow-deer, there is activation in reproductive potential, which is the part of the strategy in competition for resources and indicates its wider ecological lability in comparison with the red-deer. Meanwhile, a high level of adaptation to the conditions of the open steppe is noted in the moufflon, which (together with high reproductive capacity) rationally uses pasture potentials while the fallow-deer and red-deer have a certain level of stenophagy.