Milk secretion in marine mammals in relation to foraging: can milk fatty acids predict diet?

• Main Author: Iverson, Sara J
• Format: Book Part
• Language: unknown
• Published: Oxford University PressOxford 1993
• Subjects: Antarc*; Antarctic; Antarctic Fur Seal; harbour seal; hooded seal
• Online Access: http://dx.doi.org/10.1093/oso/9780198540694.003.0015; https://academic.oup.com/book/chapter-pdf/52430150/isbn-9780198540694-book-part-15.pdf

Abstract Patterns of milk composition and delivery differ greatly among mammals. However, despite these species-specific differences, lactation is very expensive in all species and thus diet and nutrient reserves of individual females must play a critical role in lactation performance. Pinnipeds, as well as mysticete whales, exhibit extreme adaptations to the constraints imposed by the separation of maternal feeding from milk transfer. This paper will consider three main questions: (1) how are milk secretion processes adapted to the temporal separation of foraging and milk secretion; (2) how are changes in diet or nutrient reserves likely to affect milk composition or yield; and (3) can specific milk constituents be used to indicate foraging behaviour or diet of individual animals? Substantial quantities of nutrients and metabolites are required by the mammary gland for the secretion of milk constituents. Nutrient partitioning and milk secretion are physiological processes which are both highly regulated and biochemically constrained. The general principles of these processes appear to be shared among all mammals, including marine mammals. It is concluded that neither the levels nor the types of most milk constituents are likely to be affected by maternal diet in marine mammals. However, milk yield may be reduced during a low plane of nutrition. Unlike other constituents, such as protein or carbohydrate, dietary fatty acids essentially remain intact through the digestion process (in carnivorous mammals) and many of these are secreted in milk or deposited in adipose tissue with no or minimal modification. Recent studies on species such as the California sea lion, Antarctic fur seal, hooded seal and harbour seal suggest a strong potential for determining prey items and diet of marine mammals through fatty acid signatures in the milk, particularly given the complex array of fatty acids which exist in marine organisms.