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Comparisons are made using empirically determined flight costs. Flight costs and the amount of work per unit distance increase with body mass, but cost per unit weight and the dimensionless costs of transport (energy required to transport 1 N over 1 m, COT) decrease. A simple allometric equation predicts an upper limit for flight costs in birds. Several groups are capable to flying at cheaper rates. COT values of insects, bats, birds, and aircraft are compared. Albatrosses are the world’s cheapest flyers. COTs of vertebrates and aircraft decrease with increasing mass. This is not the case for insects. Flight costs expressed as multiples of basal metabolic rates vary from a few times for frequent flyers to up to almost 19 times. The ratio of mechanical power calculated using aerodynamic models over empirically determined metabolic power roughly increases with mass. The cost of hovering of hummingbirds increases linearly with body mass.

This chapter describes various techniques for measuring metabolic rates of unrestrained organisms in the field. These include stable isotope techniques, which allow the accurate measurement of the carbon dioxide production of wild animals, over an interval ranging from a few hours to a few days. The main disadvantage in the method is that the measurement is integrative and the organism must be captured on at least two occasions. Alternative techniques for real-time measurement of metabolic rates utilizing flow-through respirometry in wild, unrestrained animals are described, including representative case studies measuring hovering metabolism in wild hummingbirds, the foraging energetics of ants in the wild, and the energetics of nest building in wasps.

This chapter addresses the question of optimal temperatures by looking at the evidence from physiological and ecological studies—evidence from studying living organisms. It summarizes what is known about the effects of temperature on growth, metabolic rates, primary production, biomass, and biodiversity. In each case, the overall tendency is a positive correlation with temperature—higher values at higher temperatures, lower values at lower temperatures. There are however plenty of exceptions, such as biomass and primary production in the sea and in deserts, and biodiversity in shallow versus deep seafloor muds. By building toward a mechanistic understanding of temperature effects, this study can overcome the habitat commitment obstacle.

This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push-mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.

This chapter describes the setup, the plumbing, and the equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull-mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.

This chapter argues for a two-dimensional, energetically-based view of population equilibrium, and this view is supported by two large-scale observations. It suggests that thinking about equilibrium simply as a balance between births and deaths is too simplistic. Rather, equilibrium is a balance between rates of energy use and rates of consumption, with both birth and death rates a consequence of these more fundamental metabolic considerations.

This chapter reviews epidemiologic studies on metabolic and hormonal predictors of obesity. It focuses primarily on prospective cohort studies, first discussing metabolic predictors, including resting metabolic rate (RMR), respiratory quotient (RQ), and insulin sensitivity, and then examining studies of hormonal predictors (such as ghrelin, leptin, and adiponectin) of obesity. For inflammatory cytokines, the chapter reviews recent prospective studies on C-reactive protein (CRP) and fibrinogen. Finally, it discusses the relationship between the stress hormone cortisol and adiposity.

This chapter examines the paleophysiology of nonavian dinosaurs. It describes the physiological and functional aspects of dinosaurs and focuses on two distinct physiological attributes: thermoregulation and aerobic capacity. New evidence pertaining to dinosaur energetics and thermoregulation is examined. The chapter discusses respiratory turbinates, resting metabolic rates, lung structure, ventilation, elevated active metabolic rates, and the relationship between bone microstructure and thermoregulation in nonavian dinosaurs.

The previous two chapters discussed how the size scaling of foraging and metabolic rates affected the dynamics of consumer-resource systems. Using different modeling approaches, it was shown that stage-dependent competitive ability was the main predictor of population dynamics; that is, it largely set the conditions for different types of cycles to occur. This chapter adds another intraspecific interaction on top of the consumer-resource system, namely, cannibalism. It uses a discrete-continuous population-level model based on individual-level net-production energetics to investigate the effects of cannibalism. The focus will be on the effects of cannibalism on population dynamics related to four processes that have been discussed in the literature regarding cannibalism: effects on mortality, competition, energy gain, and the size dependence of interactions.

This chapter discusses experimental approaches used to study the ecology and physiology of the critically endangered leatherback sea turtle (Dermochelys coriacea). It describes the measurement of field metabolic rates (FMRs) of leatherbacks using the doubly-labeled-water (DLW) method. It also discusses how to estimate FMRs based on aerobic dive limits and similarities in the behavior and physiology of two different species.

This chapter presents METE, a comprehensive, parsimonious, and testable theory of the distribution, abundance, and energetics of species across spatial scales. It develops the structure and predictions of the theory. These predictions include species abundance distributions, species–area relationships, distributions of metabolic rates across individuals, abundance–metabolic rate relationships, and spatial distribution patterns for individuals within species. Predictions all stem from prior knowledge of four ecological state variables – area, species richness, total abundance, and total metabolic rate – which are to ecology what pressure, volume, and temperature are to thermodynamics.

This chapter discusses the energy balance and physiological homeostasis of incubating birds, ranging from taxonomic, geographical and life-history related variation in energy costs of incubation, to thermal considerations for birds on the nest, links between energy expenditure and fitness, and non-energetic costs of incubation. Energy costs of incubation amount to 3.4 times the basal metabolic rate (BMR). This is 15% lower than the cost of chick-rearing (2.9 × BMR) for all birds, but similar to chick-rearing costs in species with female-only incubation. Energy costs are typically higher in challenging conditions, which can impair fitness of parents and offspring. The chapter speculates on the physiological basis for this, and discusses how costs to parents may carry over to also affect nestling performance. The chapter ends by drawing attention to situations where the primary currency for incubation is not energy-based, which we exemplify by discussing the water economy of incubating desert birds.

This chapter explores the ubiquitous phenomenon of scaling in biology through the lenses of biomechanics and statistics. Pragmatic approaches to answering questions in comparative biology often involve summarizing complex phenomena by the relationship between two key variables. For example, the multitude of factors affecting metabolic rate have often been condensed into a simple scaling relationship relating metabolic rate to body mass. This procedure is fraught with difficulties, especially if — as is often the case in biomechanics — a statistical relationship between variables is mistakenly interpreted as a functional one. The obvious difficulty here is that most physical relationships in biology are inherently multi-dimensional. Summarizing the relationship between two physical variables as a simple power law relationship therefore means that some, or even most, of the scatter about the line of best fit must inevitably result from the physical incompleteness associated with projecting multi-dimensional data onto two dimensions. This component of the scatter represents not measurement error, but equation error, resulting from a deficiency in the fitted equation. The chapter discusses appropriate methods of statistical analysis in this case, and concludes that the errors-in-variables models that have been recommended for estimating scaling relationships in biomechanics are not the appropriate mode of analysis. The West-Brown-Enquist model of metabolic scaling is re-derived in a simple and intuitive fashion, and is used to illustrate the statistical and conceptual difficulties inherent in any bivariate scaling analysis of a physical relationship that actually involves many more than two variables.

Animals can be considered as drought evaders, drought evaporators, or drought endurers. Evaders are small desert animals that avoid overheating of the body on hot sunny days and minimize the need for cooling by evaporative water loss. Evaporators depend on sufficient water intake to enable them to cool their body temperatures by evaporation. Few of these can survive in deserts, and those that do live on the edges of deserts. Endurers are usually very large animals that can endure high temperatures. Many desert animals employ heat shock proteins to minimize the effects of overheating and also use unique strategies to increase excretion of salts. Many related desert taxa employ a suite of characteristics that make them tolerant of high temperatures. To determine whether these characteristics are adaptive requires removing the effects of phylogeny to know which characteristics are special to desert environments.

The calorie norm set up by the FAO to delineate the undernourished in a population has, as its foundation, estimates of the minimum calorie‐expenditure requirements of individuals of different ages and sexes, which are subsequently aggregated to the household level (see Ch. 9). The individuals’ minimum calorie requirements are those needed to maintain the lowest body weight that medical studies have found to be consistent with unimpaired health and also to pursue some relatively light physical (work) activity. In this chapter, the many difficulties encountered in the estimations of these minimum requirements are analysed. It is further revealed that the FAO has based its requirements for adults on obsolete data on the basal metabolic rate (BMR), taken from sample populations that are not representative for people living in a tropical climate. The FAO has hence overestimated the calorie requirement in its norm by some 10%.

This chapter describes various techniques for measuring metabolic rates of unrestrained organisms in the field. These include stable isotope techniques, which allow the accurate measurement of the carbon dioxide production of wild animals over an interval ranging from a few hours to several days. The main disadvantage of the method is that the measurement is integrative and the organism must be captured on at least two occasions. Alternative techniques for real-time measurement of metabolic rates utilizing flow-through respirometry in wild, unrestrained animals are described, including representative case studies measuring hovering metabolism in wild hummingbirds, the foraging energetics of ants in the wild, and the energetics of nest building in wasps.