Abstract—A field survey of snow leopard (Panthera uncia) habitats was carried out in the southeastern part of the Eastern Sayan Mountains (Okinskii and Tunkinskii districts of the Republic of Buryatia and the Kaa-Khemskii district of Tuva Republic). Seven or eight adult snow leopards were observed as constant inhabitants of the Tunkinskie Gol’tsy, Munku-Sardyk, and Bol’shoi Sayan mountain ridges. The presence of eight snow leopards was confirmed using DNA-based analyses of scats collected in 2014–2016. The main prey species of the snow leopard in Eastern Sayan is the Siberian ibex (Capra sibirica), but its abundance has steadily decreased over the past 20 years. The red deer (Cervus elaphus) and the wild boar (Sus scrofa), which were some of the most numerous ungulates in the survey area, are replacing the Siberian ibex in the snow leopard’s diet. In addition, the mountain hare (Lepus timidus) is also of importance to the snow leopard’s diet.