Marine mammal physiology: requisites for ocean living

When confronted for the first time with studying the biology of marine mammals, many students are initially drawn in by the legends, lore, and intrigue of marine species. They certainly are “charismatic megafauna,” and their photos and stories adorn numerouswebsites and books. Their high visibility on display at aquaria gives the public a small glimpse into their lives, but also may feed a tendency to produce polarizing opinions oissues. These sometimes high-profile issues are numerous, from subsistence and commercial hunting, classification and handling of endangered species, local and international conflicts with fisheries, to sport boating and military operations. It is no wonder that many people from around the world have some knowledge of whales, seals, walruses, otters, and more. There are many publications and books that cover these specie from almost all perspectives and we include some of those reference works for your consideration. This textbook, however, takes a step back, to focus on the physiological and biochemical characteristics that have allowed these mammals as a group to effectively exploit the marine environment that is so hostile to humans. While there are thousands of individual scientific papers and research-focused books that have asked this question in extreme detail, we have compiled a series of larger discussions aimed at the student interested in the general aspects of physiology and biochemical adaptation of marine mammal species. The authors have focused on the key challenges that a marine mammal must overcome by living in the ocean, and how they have evolved and adapted biological systems to successfully live where no other mammals can follow. Our contributing authors come from a wide spectrum of academia, government, industry, and veterinary science, however, all are experienced teachers in their respective fields, and this book is written with that focus in mind. We hope to appeal to a broad range of students, from those that are new to marine mammals, in general, to those that are well into a focused graduate program and need a broader frame of reference. Our author pairings are specifically tailored to have mentors and up-and-coming researchers working together to provide a perspective that is relevant to multiple generations of scientists. The approach was intentionally international, such that our expertise reflected this group of mammals with global distribution. We cover the fundamental physiological, biochemical, and anatomical “tricks” that have evolved in many species of marine mammals. We discuss variations in those adaptations, through a range of species. For example, the water balance issues facing a newly weaned, fasting elephant seal pup on a California beach are not the same as those facing a whale on a long migration, yet they approach it in a remarkably consistent fashion. The hydrodynamic design of a swimming walrus is not very similar to that of a high-speed dolphin, but they are both constrained by the forces of drag, lift, and buoyancy. Each chapter has a “Toolbox” section where the authors discuss many of the newest methods for working on the physiology of marine mammals. In short, we are asking you to consider the following questions: If you were designing a marine mammal, what would you need to think about to allow it to live in the ocean? How would you keep it warm? What would you design to allow it to dive for very long periods, to extreme depths? Where would it find water to drink? How would you minimize the cost of swimming and how would it find its prey in the deep and dark? These questions and more are throughout this book. As with all research, we expect that for every question answered, you will ask several more.