PRENATAL MATERNAL INVESTMENT IN OFFSPRING OF NORTHERN FUR-SEAL CALLORHINUS-URSINUS (OTARIIDAE, PINNIPEDIA)

Length and weight are found to be minimum in newborn pups of northern fur seal born by young females. These parameters show a tendency to increase with age of mothers. These parameters reach maximum when the offspring is produced by middle-aged mothers. A decline in the birth-weight of male-pups born by females aged over 12 years was noted, whereas the female birtheweight remained constant. Weight of males and females al birth averaged respectively 16,1 and 14,5% of the weight of their mathers after reproduction increasing with the increase in mother's weight. However, this correlation seems to be insufficient. The relative birth-weight showed significant negative correlation with material weight (r - -0,68 + 0,14; p < 0,001) and age (r - -0,49 + 0,17; p < 0,001). Mean age of breeding females decreases from 14,2 to 7,8 years during the pupping period. Observations of many years show significant positive correlation between the mass of newborn pups and the date of their birth.