Demographic characteristics of an unhunted Dall sheep ( Ovis dalli dalli ) population in southwest Yukon, Canada

• Published in: Canadian Journal of Zoology
• Main Authors: Hoefs, Manfred, Bayer, Max
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1983
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Yukon; Canada; Kluane National Park
• Online Access: http://dx.doi.org/10.1139/z83-181; http://www.nrcresearchpress.com/doi/pdf/10.1139/z83-181

The demographic characteristics of an unexploited Dall sheep population, which inhabits the Sheep Mountain area of the newly established Kluane National Park, are described for the period 1969 to 1980. During this 12-year interval the average population size was 225.8 sheep in June–July, but fluctuations about this mean value of up to 17% were observed; peaks of 256 and 244 were reached in 1971 and 1979, respectively, and a low of 184 was observed in 1977. Variations in population size were caused primarily by differing numbers of lambs and yearlings. The population components averaged as follows: 68.4 males (≥ 3 years), 10.9 males (2 years), 81.1 females (≥ 3 years), 11.1 females (2 years), 24.0 yearlings, and 30.3 lambs. It is assumed that some variation in population size can be expected because of variation in forage production of this population's winter range that is filled to capacity. However, the decline of the population in the mid 1970s was assumed to be caused by increased disturbance and adverse impact by feral horses. A life table for the ram component of this population is constructed. The mean mortality rate of rams from birth was 24.0% and the mean recruitment rate (yearlings to adults 2+ years old) was 15.3%. The population is characterized by low productivity, high survival rate of lambs, and a short maximum life expectancy.