Blubber

This chapter describes blubber, a dense vascularized layer of fat beneath the skin and one of the most well-known and universal characteristics of marine mammals. Although it is not strictly present in polar bears (. Ursus maritimus) or sea otters (. Enhydra lutris), all cetaceans, sirenians, and pinnipeds have blubber and it may comprise up to 50% of the body mass of some species at certain life stages. Blubber has long been recognized as the primary and most important site of fat, and thus also energy storage in marine mammals. However, blubber also has a number of other important functions. The blubber layer serves as an insulator in mammals living in often cold marine environments and is thus central to their entire process of thermoregulation. Blubber also affects buoyancy and functions as a body streamliner and elastic spring for efficient hydrodynamic locomotion. Although blubber is a dynamic tissue, which can reflect both nutritional state and life history stage of individuals, the tissue itself has likely evolved to best suit the lifestyles, stresses, and constraints of specific groups and even individual species of marine mammals. Hence, the study of blubber can provide unique insights not only into phylogenetic relationships and environmental adaptations but also into aspects of individual feeding habits, foraging ecology, species distribution, and demography that are otherwise difficult to study. © 2009