Milk fatty acid composition of perinatal and foraging Steller sea lions: examination from pup stomachs

Abstract

To investigate the relationship of milk fatty acid composition between perinatal and foraging Steller sea lions and within each maternal state (i.e., perinatal or foraging), milk samples were collected in 2010 and 2011 via gastric intubation from Steller sea lion pups on a small rookery in the central Gulf of Alaska. Subsamples of initial milk samples were taken over four hours post-collection to examine changes of fatty acids within milk over time. Maternal states of lactating females of sampled pups were determined via remotely operated video cameras on the rookery. Fatty acid composition within milk, collected from Steller sea lion pup stomachs, did not change over the four hour post-collection period, and thus milk fatty acids were not modified within milk over time. Milk fatty acid composition between Steller sea lion maternal states was different, and thus can be utilized to distinguish between perinatal and foraging Steller sea lions of the same geographic region. In the absence of direct observations, this study demonstrated the use of a viable method to determine maternal state. Milk fatty acid composition remained relatively constant within perinatal Steller sea lions, suggesting steady mobilization of fatty acids from blubber to milk, and within foraging Steller sea lions, implying females forage in the vicinity of the rookery and on similar prey species. Differences in milk fatty acid composition between maternal states, including differences in the relative percentages of polyunsaturated fatty acids, may have implications for growth and development of offspring. For lactating Steller sea lions, foraging after the perinatal period is important for continued delivery of fatty acids needed by young pups.