[Age changes in the sexual size dimorphism in sables in nature and captivity].

Inter-sexual differences in craniometric parameters were studied in sables of varying sex and age in natural (n = 2338) and farm (n = 516) populations. In nature, the differences between the skull size in males and females are, as a rule, high (p < 0.001) and the size dynamics correlate well with age. In the cell population, the difference in the skull size between the sexes is statistically significant (p < 0.01), but the correlation of sizes with age is absent. In natural populations, parameters of sexual dimorphism (SD) correlate positively with age, with a maximum correlation found in the animals aged nine and a minimum found in yearlings. The index of sexual dimorphism grows considerably until three years of age, after which the dynamics resemble a cyclical process with a repetition of maximum values each fourth year with a general trend of growth in the parameter. The highest values of SD in cell sables are registered at 3-5 years of age, while the minimum ones are noted in the age groups of 6-9 and 13-14 years of age. In nature, yearlings aged 6-10 months are characterized by a tendency to general growth (which is not manifested in the introduced population from the basin of the Vakh River) and increase in the SD index with age. The Vakh population is characterized by a decrease in the SD index. The specific rate of skull growth in males is 1.8-fold higher than in females. The age dynamics of the sizes and the vectors of rates between the sexes are not in accordance, as a rule. The results of our study correspond to the theory by Geodakyan (1991) about dichronomorphism. In our opinion, the differences in age manifestations of sexual dimorphism and postnatal skull growth in natural and farm sable populations are determined by the different directions of selection.