Manfred Hoefs and Ian McTaggart Cowan: Ecological Investigation of a Population of Dall Sheep (Ovis dalli dalli Nelson) An investigation was carried out on a population of Dall sheep and their range in Kluane National Park, southwest Yukon Territory. Population dynamics data for the herd were collected from 1969 to 1973, during which time the number of adult sheep remained fairly stable at around 200 animals. Statistics presented include such parameters as natality and mortality rates and factors, sex ratios, productivity, density, and migration patterns. Historical information on this population is reviewed. A life table and a population structure are developed from which management decisions can be derived and prediction be made on the impact of various harvest strategies. The response of sheep to some environmental variables as temperature, wind, wind chill, and snow depths is analysed. Feeding behaviour, forage species, and range use patterns over the annual cycle are described. The hypothesis is developed that the winter range of the population is occupied at capacity level.