Maternal Investment and Neonatal Growth in Phocid Seals

Abstract

(1) This paper draws together information on neonatal size at birth, weaning mass, growth rates during the nursing period and duration of lactation of phocid seals in order to examine similarities and differences in these aspects of life-history patterns within the group. Broader interspecific comparisons are also made in order to evaluate the adaptive developmental responses of phocid seals during the period of maternal investment in contrast to terrestrial carnivores and to mammals generally. (2) Individual phocid offspring of most species are large and precocial, but female phocid seals as a group do not invest more energy per litter than many other carnivores and not substantially more than mammals generally at the time of parturition. (3) The relative mass of individual phocid seals at weaning is more uniform within the group than is mass at birth. This similarity is achieved by compensatory variation of growth rates and the duration of lactation. (4) Although data are limited, it appears that maternal investment differs between the sexes in all species which are sexually dimorphic with respect to body size.