The behavioral ecology of air breathing by aquatic animals

Abstract

Behavioral ecology uses general principles of economic design to generate testable predictions for animal activities in particular environmental situations. Sociobiology and optimal foraging, the two most developed areas of behavioral ecology, use very similar models of resource gain maximization to investigate patterns of mating and energy acquisition, respectively. Here, I consider the relevance of these principles to the uptake of oxygen by air-breathing aquatic organisms. The behavior of bumblebees foraging for foxglove nectar illustrates the principle of optimal exploitation of aggregated resources. When applied to the acquisition of oxygen at the water surface by diving animals, this principle predicts that with increasing distance to feeding sites or other areas of resource gain, the bout lengths of surface time and dive time will increase, as will percent time at the surface; swimming speed may increase or decrease depending on the costs of acceleration. Principles of the allocation of effort predict that in bimodal organisms the use of air will decrease and the use of dissolved oxygen will increase as depth increases. Empirical field and laboratory studies provide some support for these predictions in a variety of mammals, birds, reptiles, amphibians, and fishes. A "theory of optimal breathing" is relevant to physiology because it uncovers interesting and unexpected subtleties in the regulation of respiration, because it provides a holistic framework in which to order empirical findings, because it pinpoints potentially confounding variables in experimental studies, and because it illustrates the value of a hypothetico-deductive approach to adaptation.