Lipid and fatty acid profiles of migrating Southern Hemisphere humpback whales Megaptera novaeangliae

The lipid and fatty acid (FA) composition of the outer blubber layer was characterized in 46 east Australian migrating humpback whales Megaptera novaeangliae. Samples were obtained at 2 time points of the annual migration, which occurs between Antarctic feeding grounds and low-latitude breeding grounds and is associated with a prolonged period of fasting. Blubber lipid composition was dominated by triacylglycerols in all individuals, and the FA profiles of both migration cohorts and sexes were dominated by monounsaturated fatty acids (MUFA). Results indicate that males primarily mobilise polyunsaturated fatty acids in response to migration and fasting, favouring the most readily utilisable FA as governed by their physicochemical properties. In comparison, females appear to initially mobilise short-chain (<18 carbons) MUFA stores, potentially to attend to dependent calves' thermoregulatory needs. Feeding ecology investigations suggested that humpback whales have a species-specific FA composition of their blubber, including a detectable influence of their diet. This study provides the first insight into lipid and FA profiles of Southern Hemisphere humpback whales. A comprehensive understanding of FA dynamics, especially during times of energy deficit, is essential for understanding the nutritional status of Southern Hemisphere humpback whales and thereby the risks posed by growing environmental threats including toxic and persistent lipophilic pollutants.