Range Relationships of Feral Horses with Wild Ungulates and Cattle in Western Alberta

Abstract

Spatial and foraging relationships between feral horses and coexisting ungulates were studied in the foothills of western Alberta. Distribution patterns of horses were compared to those of cattle, elk (Cervus elaphus), deer (Odocoileus hemionus and 0. virginianus), and moose (Afces alces) using indices of spatial and habitat use overlap. Horses were more ubiquitous in their distribution than any other ungulate and utilized sites also used by other species. Lack of behavioural interactions and dietary differences suggested ecological separation of horses from deer and moose. Although horses and elk both used dry grasslands during winter and spring, competition for forage was minimal due to the low number of elk present. During spring horses occupied some areas later preferred by cattle but range use was not excessive prior to the turn-out of cattle. There was little contemporaneous spatial overlap of horses and cattle even though their summer diets showed 66% overlap. Potential for competition appeared highest between horses and cattle but grazing relationships were complex. The growing body of knowledge concerning the ecology of feral horses includes several comparative studies on diets of horses, domestic stock and native ungulates (Hubbard and Hansen 1976; Hansen and Clark 1977; Hansen et al. 1977; Olsen and Hansen 1977). A commonly expressed rationale is the need to determine carrying capacities for various combinations of herbivores. However, dietary overlap is important only if accompanied by spatial overlap, Authors are graduate student and associate professor, Dept. of Animal Science, University of Alberta, Edmonton, Alberta, T6G 2E3. Financial support was through the Forest Development Research Trust Fund, Alberta Forest Service. The authors thank G. Erickson for field assistance during the initial phases of the study. Manuscript received January IO, 1979. 266 JOURNAL OF RANGE MANAGEMENT 33(4), July 1980 if shared foods are in short supply, or if one herbivore limits access of another to a preferred food source. We report here results of a study to determine the extent of spatial, habitat use and dietary overlap between feral horses and other ungulates in western Alberta, and to determine levels of range utilization.