Historical Trends in Mountain Sheep Populations and Their Habitats

Our objective is to present the historical trends for mountain sheep (bighorn sheep [ Ovis canadensis ], thinhorn [ Ovis dalli ]) in North America. Early accounts suggest populations of mountain sheep in Alaska, mountain ranges in western North America, and deserts in the United States and Mexico, at the arrival of early explorers and settlers. Native Peoples did not negatively affect populations of mountain sheep to the extent of the consumptive activities of early Europeans. As Western settlement progressed, mountain sheep populations declined dramatically, with the consensus that this was due to unregulated subsistence and market hunting, excessive livestock grazing, mining, recreation, and unfavorable weather patterns. The then-unknown effects of domestic sheep pathogens likely played the single largest part in mountain sheep population declines and extirpations. The result is that mountain sheep were rare in most areas of the United States by the close of the 1800s and in parts of Canada by the early 1900s. This motivated management changes in some areas to make the landscape more conducive to restoration of mountain sheep populations through the middle and later 1900s. Land-use changes and increasingly effective harvest restrictions allowed bighorn sheep populations to rebound throughout the 1960s and peak in different areas in the late 1970s through the early 1980s, because of reintroduction and translocation efforts. By the mid-1990s and continuing into the early 2000s, population trends in bighorns had again shifted, with some jurisdictions experiencing declines in mountain sheep populations. American mountain sheep presently number less than a quarter million, while most of the other big game species surpass a million. Mountain sheep conservation and management have been a success. Fortunately, widespread conservation efforts and the application of innovative management techniques have assisted with increasing mountain sheep populations in the United States, Canada, and the deserts of Mexico.