Growth of grey seal (<i>Halichoerus grypus</i>) neonates: differential maternal investment in the sexes

Abstract

Male grey seals are larger at birth, grow faster during the nursing period, and are weaned at a heavier mass than females. Estimated mean energy expenditure by females from conception to the time of weaning (maternal investment), including the heat increment of gestation, cost of foetal tissue, and energy contained in milk acquired during the nursing period, was greater for male than for female offspring. This pattern of energy investment by female grey seals in their young is consistent with Maynard Smith's model of sexual investment (J. Maynard Smith. Behav. Ecol. Sociobiol. 7: 247–251. 1980).