An age structure and a reevaluation of the population dynamics of Dall sheep (Ovis dalli dalli)

Abstract

Population numbers, distribution, composition, and age structure of Dali sheep (Ovis dalli dalli) were studied in Mount McKinley National Park in the summer of 1972. Age of males was estimated by counting horn annuli and by multiple regression analysis based on the correlation of age with horn size. Composition ratios and tho sample of males whose ages were estimated were used to establish the age structure of the living population. The results demonstrate that the age structure has not been stationary over the past several years. Differences in numbers in each age class are due to marked variability in initial size and in mortality rates of the cohorts comprising the population. Analysis of the carcass data of Murie (1944), which has been widely used in the construction of life tables, showed that the age structure was not stationary during the period those carcasses accumulated. Changes in distribution indicate that timing of movements is variable and fidelity of individuals to specific seasonal ranges is low. Numbers and the age structure have fluctuated dramatically since the mid-1920's, The consequence of this variability on individual reproductive strategies is discussed.