The Effect of El Niño on Pup Development in the California Sea Lion (Zalophus californianus) I. Early Postnatal Growth

Abstract

Environmental conditions that alter the nutritional status of lactating females, or the amount of foraging time needed to maintain good nutritional status, may secondarily affect the development of their suckling young although the evidence for this is equivocal. It has been suggested that the best single measure of development of an organism is postnatal mass change (Layne 1968). Among mammalian young that feed solely on maternal milk during lactation a net accumulation of mass is possible only if nutrient transfer from the mother exceeds the maintenance requirements of the young. Maternal food shortage can cause a reduction in milk transfer (Loudon and Kay 1984; Oftedal 1985) and thus in the nutrients available for gain in mass by suckling offspring.