Mathematical modeling of the variation in the survival of female northern fur seals, Callorhinus ursinus (Linnaeus, 1758), on Tyuleniy Island

Resumo

The dynamics of the survival and number of female northern fur seals, Callorhinus ursinus, on Tyuleniy Island have been studied. The data on the age structure and physiological condition of females (obtained during observations in 1958–1988) were used to estimate the model parameters. The adequacy of the model estimates of female number was evaluated using the data on the number of newborn pups at the rookery in 1958–2013. It has been found that a reduction in the survival rate of individuals of younger age groups, a decrease in the proportion of females, as well as aging of the population occurred in the 1958–1988 period. The use of numerical simulation methods shows that the rate of survival of females among individuals under 3 years of age increased substantially after 1988, indicating a positive trend in the dynamics of their number.