Abstract

Gatten, R., Miller, K. and Full, R.J. 1992. Locomotion energetics at rest and during exercise. In Environmental Physiology of Amphibians. (eds. M.E. Feder and W. Burggren). University of Chicago Press. New York. pp. 275-377.

Amphibians are well known for their generally quiescent and inconspicuous lifestyles and for their low annual use of energy (Pough 1983). At times in their life cycle, however, most amphibians engage in increased levels of activity and energy expenditure. Short periods of intense effort may be important in escaping from predators (Blem, Steiner, and Miller 1978; Formanowicz et al. 1981). Longer intervals of sustained locomotion may be vital for reproduction (Magnusson and Windie 1988). The major purpose of this chapter is to summarize what is known about the rates at which amphibians use energy for such short-term and long-term movements, and to consider the factors that influence those rates of energy use. Before such an assessment is possible, we must know the rate of energy use by amphibians at rest. Therefore, we first address the minimal energetic cost of living for amphibians. We then turn to the energetics of sustained locomotion and finally to the cost of brief, intense, nonsustainable movement. In focusing on the energetics of locomotion, we intentionally exclude many topics (such as muscle biochemistry and increased respiratory and cardiovascular function) that are closely related to the ability of amphibians to use energy during exercise. We do so both out of practical necessity and because such topics are included elsewhere in this volume or because recent reviews of such topics are available. Various aspects of the energetics of amphibians at rest or during exercise have previously been reviewed by Bennett (1978, 1980a, 1984, 1985, 1986), Gatten (1985), Paladino (1985), Pough (1983), Seale (1987), Taigen (1983), and Taigen and Pough (1985). Throughout this chapter we pay special attention to two factors, body temperature and body mass, that have an extraordinarily important influence on the energetics of amphibians. Although many authors have considered the effect of body temperature on the resting metabolic rate of amphibians (see chapter 8), no comprehensive analyses describe how temperature affects energy use during locomotion. Some authors have described the influence of body mass on the resting and/or exercise oxygen consumption of amphibians (Feder 1976a; Taigen 1983; Whitford and Hutchison 1967; and Withers and Hillman 1981); in this chapter, however, we conduct a comprehensive review of all the data that bear on this topic. The major taxonormc groups of amphibians (anurans, dans, and salamanders) have been separated evolutionarily for at least 250 million years (Pough 1983). Thus, extant rep~sentatives of these groups may reveal an evolutionary divergence in the cost of living in these animals. We focus on ~ this question in our analyses of resting metabolism, the cost of sustained locomotion, and the energetics of short-term, intense exercise. - As were the editors (chapter l) and other contributors to this book, we were struck by the strong bias of investigators towards easily obtainable species, especially those from the temperate zones of Europe and North America, where most of the research on the topic of our review has been carried out. Our analyses and conclusions are thus based on data from relatively few species. We make no attempt to correct for this bias. Throughout the chapter, we explicifly state the limits of the data; readers should consider the implications of these limits and avoid the dangers of unwarranted extrapolation beyond these limits.

In this chapter we make little direct reference to studies of the actual Iocomotor performance of amphibians. Such material is reviewed primarily in chapters 11, 14, and 16. However, wherever possible we include such information where it directly pertains to data on the energetic cost of movement. Finally, it should be noted that our analyses of the energetics of locomotion pertain to data from animals moving in a laboratory setting in relatively controlled, stemtyped, and perhaps unnatural ways. In chapter 14, Pough and coauthor consider the energetic cost of locomotion and other behavior in more natural surroundings.