Great Basin Naturalist


Mountain goat (Oreamnos americanus) and bighorn sheep (Ovis canadensis) ranges overlap substantially in northwestern United States and southwestern Canada. Resource overlap in food and habitat parameters is assumed, but the degree of overlap has not been estimated. Data from published separate and comparative studies on food and habitat use were used to calculate indices of resource overlap for goats and sheep. Indices of overlap for general forage classes (grasses, forbs, browse) were >0.90 in summer and winter for data based on pooled data from separate studies and in summer for data for comparative studies. In winter for comparative studies this overlap was 0.64. For studies where forage species were identified, estimates of resource overlap from separate studies were ~0.8 but were <0.5 for comparative studies. Indices of overlap for habitat variables were also low (<0.7) for comparative studies. It was concluded that possible overlap in food and habitat use by goats and sheep could be extensive; but in sympatric populations resource overlap may be reduced substantially.