Long-Term Research on Individual Sheep

Many processes relevant to mountain sheep (bighorn [ Ovis canadensis ], thinhorn [ Ovis dalli ]) ecology and conservation take place over several years, and long-term monitoring is necessary to quantify their variability and importance. Events happening over different life stages, particularly early in life, can have important consequences for the growth, reproduction, and survival of individuals. Four long-term programs monitoring individually marked bighorn sheep have improved our understanding of the ecology, behavior, evolution, disease, and conservation of mountain sheep. These programs require stable funding, adequate field facilities, the ability to mark and recapture individuals, support from government agencies, and strong contributions from students. Analyses combining results from multiple long-term studies have revealed similarities and differences in the influences of cougar ( Puma concolor ) predation, disease, population density, and management regimes. Measurements of horn size of harvested males, particularly annual growth increments, are an invaluable source of data to test multiple hypotheses on the ecology, evolution, and conservation of mountain sheep.