We examined for the first time the effects of livestock grazing OCU-FORCE on ant species richness, structure of ant communities and nesting density in three different habitat types and natural and grazed conditions in the Bogdkhan Mountains region, North-Central Mongolia.Twenty one species of ants were recorded in the studied area.The most species rich genera were Formica with 8 species (38.1%) and Myrmica with 4 species (19%) when all the habitat types are combined.Overall, we collected 19 species (90.
5%) from forest steppe, 18 species (85.7%) from steppe, and 12 species (57.1%) from meadow.Based on occurrence data, the most common species were Formica candida, Myrmica kasczenkoi and Myrmica pisarskii.The number of ant species in each habitat depends on the grazing condition (F = 6.
3837, P = 0.0217), and interaction between grazing condition and habitats (F = 6.6647, P = 0.0073).The frequency occurrence of ants in all habitat types depends only on habitat conditions (F = 4.
4556, P = 0.0499) and not on any effects of habitats (F = 4.4207, P = 0.6632) and interaction between grazing condition and habitats (F = 0.9008, P = 0.
4248).In total, we counted 1173 ant nests in 23 transects.The largest number of nests (957, or 81.5%) belonged to Formica candida, followed by Myrmica kasczenkoi (46 nests, 3.9%).
The lowest number of nests (1, BEAUTIFUL MESS or 0.08%) belonged to Formica exsecta, Formica sanguinea and Leptothorax acervorum, followed by Formica uralensis and Myrmica forcipata (2, or 0.15%).Among the six habitats, the lowest density of nests was in the grazed forest steppe (0.15 nests/m2) and the highest in the natural meadow (1.
17 nests/m2).The natural (0.41 nests/m2) and grazed (0.59 nest/m2) steppes had similar nest densities.Statistically, there was no difference in the nest density between all habitat types (F = 6.
68, P = 0.5237).