Wildfact Library

[Sully]

Factors affecting the spatial distribution and co-occurrence

of two sympatric mountain ungulates in southern Mongolia

Abstract


Co-occurrence of ungulates in multi-species assemblages has fascinated ecologists

because these species seemingly belong to the same guild – feeding on plants.

Across large parts of the high mountains of Central Asia, ibex (Capra sibirica)

and argali (Ovis ammon), both predominantly grazers, co-occur at local and regio-

nal scales. However, little is known about the ecological and anthropogenic factors

that inuence their spatial distribution, co-occurrence and habitat use. We examined

factors affecting the distribution and co-occurrence of these two sympatric species

in Tost Tosonbumba Nature Reserve in southern Mongolia using an occupancy

modeling approach. Specically, we used single species occupancy models to

examine the inuence of road density, livestock density, terrain ruggedness and ele-

vation on occupancy of these two species separately. We then assessed how these

two species inuence each other’s distribution by using multi-species occupancy

models. The model-averaged occupancy probabilities for ibex and argali were

0.64  0.3

SE and 0.44  0.2 SE, respectively. Terrain ruggedness positively inu-

enced ibex distribution, while it negatively affected the occupancy of argali. We

found limited evidence of relationship with factors associated with human distur-

bance. The species interaction factor, which indicates the level of co-occurrence,

suggested that ibex and argali occurred independent of each other (φ =-

0.72  0.3

SE). Together, our results imply that there was limited co-occurrence

between the two species and that this was largely driven by terrain ruggedness at

the scale of the home range. These results suggest that topography plays an impor-
tant role in enabling these two species to co-occur at the regional scale. Reply