A big topic demands a big book, with some big thinkers behind it. When I agreed to review this book, I knew, given the authors, that I would see some big thinking, but the size of their effort took me by surprise. Physiological Ecology (all 744 pages, 2.7 liters, and 1.9 kilograms of it!) is a comprehensive yet surprisingly accessible treatment of a topic that is the linchpin for biologists of many stripes.

The authors, William H. Karasov (University of Wisconsin) and Carlos Martínez del Rio (University of Wyoming), are both physiological ecologists specializing in birds, but their book encompasses a world beyond birds that includes insects, crustaceans, fish, rats, and even giant worms and clams.

There is much of interest here for anyone concerned with key aspects of the ecological functioning of animals, with the stated target audience being advanced undergraduates, graduate students, and practicing ecologists interested in how resources are processed by animals in food webs. Here I call attention to the book's subtitle: the emphasis is on how animals process—ingest, assimilate, allocate, excrete—food. Thus, the book is a very broad treatment of animal nutritional physiology in an ecological context. So there is much missing if one imagines this tome to be a physiological ecology text, sensu lato. For example, there is little or no treatment of gas exchange and respiration, acid/base balance, thermal regulation and heat exchange, and other matters of importance in animal ecophysiology. I say this not as a criticism of their book, however, but only to highlight its scope; Karasov and Martínez del Rio do not promise to treat these subjects, and the book is thick enough as it is.

Essential to their approach are two philosophical underpinnings. One is the broad view that an understanding of evolution is key to insight in comparative physiological ecology. The other is a more narrow, pragmatic approach that emphasizes how all physiological insights are contingent on the methodological baggage that accompanies the measurements.

The authors have broken the book into six major sections. Section 1 consists of only one chapter (an overview introducing basic concepts of mass and energy budgets, allometry, temperature effects, and phylogenetic contrasts), but serves as an important synthesis of major strategies of analysis in animal physiological ecology. Section 2 also consists of only one chapter and provides a detailed overview of key biochemical aspects of animal food. Section 3 considers mechanisms of energy and material inputs to animals (with chapters on food intake, gut reactor theory, nutritional symbioses, and digestive symbioses). Section 4 follows the fate of absorbed materials to consider postabsorptive nutrient processing, the meaning of stable isotope signatures in animal tissues, and the physiology of toxin handling. Next is a section on the role of limiting nutrients, with treatments of ecological stoichiometry, of nitrogen and mineral nutrition, and of water limitation. The book closes with section 6, two comprehensive chapters dealing with energy and mass budgets as connected to growth and to reproductive output.

I found this book both fascinating and entertaining. It brings to the forefront some cutting-edge ideas in ecology and functional biology, such as metabolic scaling theory, ecological stoichiometry, and isotopic resource tracking. The emphasis on careful, phylogenetically controlled analyses in comparative studies is important and well presented. Karasov and Martínez del Rio explain difficult concepts clearly, writing in a refreshing, informal style that makes you feel you're enjoying a casual coffee with these world experts (but with high-quality diagrams on the napkins). This style will make the book especially effective as a text in upper-division animal physiological ecology courses.

That said, there are some problems. The authors rely heavily on information boxes, particularly to cover methodological approaches. Some readers will find these boxes invaluable, especially those readers new to physiological research who need to learn more about how things are done. Others will find some of them distracting, too long, or unnecessary (e.g., a box relating how a spectrophotometer works, hardly upper-division material). In reading groups such as the one in my lab, some members assigned to lead discussions of certain chapters may find themselves feeling victimized by the extreme variation in chapter length (from 27 to 93 pages). The editing in the text was generally thorough but less so in the figures and figure legends. For the most part, though, these are minor matters. The book is solid, engaging, and effective in presenting animal physiological ecology as the modern and vibrant field it is.

So if animals and food webs are central to your interests, you should read this book. But be sure to put it in your pack before your lunch. Otherwise you'll find that its 1.9 kilos will have done some preassimilatory processing of your sandwich.