Principles of Animal Locomotion

Principles of Animal Locomotion

R. McNeill Alexander
Copyright Date: 2003
Edition: STU - Student edition
Pages: 384
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    Principles of Animal Locomotion
    Book Description:

    How can geckoes walk on the ceiling and basilisk lizards run over water? What are the aerodynamic effects that enable small insects to fly? What are the relative merits of squids' jet-propelled swimming and fishes' tail-powered swimming? Why do horses change gait as they increase speed? What determines our own vertical leap? Recent technical advances have greatly increased researchers' ability to answer these questions with certainty and in detail.

    This text provides an up-to-date overview of how animals run, walk, jump, crawl, swim, soar, hover, and fly. Excluding only the tiny creatures that use cilia, it covers all animals that power their movements with muscle--from roundworms to whales, clams to elephants, and gnats to albatrosses. The introduction sets out the general rules governing all modes of animal locomotion and considers the performance criteria--such as speed, endurance, and economy--that have shaped their selection. It introduces energetics and optimality as basic principles. The text then tackles each of the major modes by which animals move on land, in water, and through air. It explains the mechanisms involved and the physical and biological forces shaping those mechanisms, paying particular attention to energy costs.

    Focusing on general principles but extensively discussing a wide variety of individual cases, this is a superb synthesis of current knowledge about animal locomotion. It will be enormously useful to advanced undergraduates, graduate students, and a range of professional biologists, physicists, and engineers.

    eISBN: 978-1-4008-4951-2
    Subjects: Biological Sciences

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-viii)
  3. Preface
    (pp. ix-xii)
  4. Chapter One The Best Way to Travel
    (pp. 1-14)

    THIS BOOK describes the movements of animals and of the structures such as legs, fins, or wings that they use for movement. It tries to explain the physical principles on which their movements depend. And it asks whether the particular structures and patterns of movement that we find in animals are better suited to their ways of life than possible alternatives. This chapter will, I hope, help us when we come to ask these questions about the merits of particular structures and movements.

    The structures of animals and some of their patterns of movement (the ones that are inherited) have...

  5. Chapter Two Muscle, the Motor
    (pp. 15-37)

    MOST ANIMAL locomotion is powered by muscles. Some very small animals including rotifers and the planktonic larvae of echinoderms, annelids, and molluscs depend on cilia for swimming, and spermatozoa swim by means of the flagella that form their tails. Small flatworms crawl by means of cilia on their ventral surfaces. Protozoans, which are not regarded as animals in modern classifications, move by means of cilia, flagella, or pseudopodia. All these are ignored in this book, which is concerned only with muscle-powered locomotion.

    The purpose of this chapter is to explain briefly how muscle works, what it can do, and how...

  6. Chapter Three Energy Requirements for Locomotion
    (pp. 38-52)

    MUSCLES HAVE TO do work whenever an animal’s body is moving against a resisting force, and whenever the mechanical energy of the body is increasing. This chapter discusses the forces and energies involved in a general way, in preparation for the discussions in later chapters of specific modes of locomotion. It also considers the relationship between the work that the muscles do and the metabolic rate of the body.

    The major components of the mechanical energy of the body that are important for discussions of locomotion are kinetic energy, gravitational potential energy, and elastic strain energy. We will consider them...

  7. Chapter Four Consequences of Size Differences
    (pp. 53-67)

    DOMESTIC CATS and lions are very different in size, but they are similar in shape and move in similar ways. Both walk to go slowly, trot at intermediate speeds, and gallop to go fast. Small minnows and large salmon are similar in shape and make similar movements when they swim. Both hummingbirds and vultures fly by beating their wings.

    There are important differences as well as similarities between the movements of animals of different sizes. In each of their gaits, lions run faster than cats and take longer strides, at a lower stride frequency. Minnows make more tail beats per...

  8. Chapter Five Methods for the Study of Locomotion
    (pp. 68-85)

    THIS CHAPTER outlines some of the principal techniques that have been used in the research that is described in later chapters. Many of them have been used in research on several different modes of locomotion, described in separate chapters. My aim is to help readers to understand what was done in the experiments that I will describe, not to supply the practical details they will need if they wish to perform similar experiments themselves.

    Cinematography or video recording is often the best way of recording movement. Cinematography has had a great deal of use in the past, but film and...

  9. Chapter Six Alternative Techniques for Locomotion on Land
    (pp. 86-102)

    THERE ARE many possible ways of traveling over land, some using legs and some not. This chapter reviews the possibilities, using very simple models to introduce the principles and to make rough estimates of energy costs. Descriptions and explanations of the movements of real animals and actual measurements of energy costs follow in later chapters.

    A few definitions are needed. A stride is a complete cycle of movement; for example, from the setting down of a foot to the next setting down of the same foot. The stride length is the distance traveled in one stride, and the stride frequency...

  10. Chapter Seven Walking, Running, and Hopping
    (pp. 103-145)

    IN CHAPTER 6, we used simple models to compare locomotion on legs with other means of moving over land. In this chapter, we will examine walking, running, and hopping in much more detail, referring much more to observations and experiments. We will be concerned with all legged animals, both tetrapods (amphibians, reptiles, birds, and mammals) and arthropods (insects, crabs, etc.).

    In almost every case, legged animals can move faster over land than animals of similar size that lack legs. Figure 7.1 shows some data for mammals. Figure 7.1A shows maximum sprint speeds, which cannot be sustained for long because they...

  11. Chapter Eight Climbing and Jumping
    (pp. 146-165)

    IT SEEMS convenient to discuss jumping and climbing in the same chapter, because some animals jump to travel in and between trees. Lemurs and other prosimian primates leap between branches; monkeys and squirrels jump to cross gaps between trees; and gibbons swing from branch to branch. Many other jumping animals do not climb. Frogs jump to travel over the ground, locusts jump to get clear of the ground at the start of a flight, fleas jump to get onto a host, and all these animals jump to escape from danger. There are also many climbing animals that do not jump,...

  12. Chapter Nine Crawling and Burrowing
    (pp. 166-180)

    FOR THE PURPOSES of this chapter, I define crawling as locomotion on land that depends principally on movements of the body rather than of limbs. Many crawling animals, such as earthworms and snakes, have no limbs. Others, such as caterpillars, have legs, but progress by bending and extending the body; the legs serve merely to anchor the anterior end of the body while posterior parts are drawn forward. An anomaly of this definition of crawling is that it excludes the crawling of human babies.

    In many cases, animals crawl and burrow using similar movements. For example, earthworms crawl and burrow...

  13. Chapter Ten Gliding and Soaring
    (pp. 181-208)

    AT THIS STAGE we turn from terrestrial locomotion to flight. Powered flight has been evolved only by insects, birds, bats, and (apparently) the extinct pterosaurs, and is the subject of later chapters. This chapter is about gliding and soaring. Insects, birds, and bats glide, and so also do various other animals, including flying fish and flying squirrels.

    This chapter starts with explanations of some of the basic principles of aerodynamics that are needed to understand flight. More detailed and authoritative accounts can be found in Prandtl and Tietjens (1957) and other textbooks of aerodynamics. Later sections of this chapter examine...

  14. Chapter Eleven Hovering
    (pp. 209-223)

    HOVERING MEANS flying so as to stay more or less stationary relative to the surrounding air. Kestrels (Falco tinnunculus, see Section 10.6) often keep themselves stationary relative to the ground by flying into the wind, matching their speed to the wind, but this is not hovering in the sense used in this chapter, because the bird is moving rapidly relative to the air.

    Many insects hover: for example, Ellington (1984) studied hovering by flies, bees, moths, a beetle, and a lacewing. Hummingbirds (masses 2–20 g) hover in front of flowers, feeding on nectar, and can sustain hovering for many...

  15. Chapter Twelve Powered Forward Flight
    (pp. 224-239)

    Insects, birds, and bats are the only modern animals capable of powered flight. All of them fly by flapping their wings.

    Helicopters and animals hover by driving air vertically downward, as explained in Chapter 11. To fly forward, they must drive air downward and backward. The horizontal component of the momentum given to the air provides the thrust force that is needed to overcome drag.

    To hover, animals beat their wings in a near-horizontal plane, with their bodies tilted at a steep angle to the horizontal (see, for example, Fig. 11.2). For forward flight, the wings beat in a more...

  16. Chapter Thirteen Moving on the Surface of Water
    (pp. 240-248)

    WATER STRIDERS (Gerris and Halobates), some other insects, and fisher spiders (Dolomedes) walk on the surface of water, supported by surface tension. Basilisk lizards (Basiliscus) run on water, relying on quite different forces. This chapter considers both these means of moving over the surface, and also discusses swimming on the surface as performed, for example, by ducks. More general aspects of swimming that apply to submerged swimmers as well as to those that swim at the surface are discussed in later chapters.

    Water striders and fisher spiders stand on water with the distal leg segments (the tarsus) resting on the...

  17. Chapter Fourteen Swimming with Oars and Hydrofoils
    (pp. 249-265)

    THIS CHAPTER is about swimming by means of limbs or fins that remain more or less flat as they move through the water. It is not concerned with animals that swim by undulation either of a fin or of the whole body; they are dealt with in the next chapter.

    A swimming animal can use its appendages to propel it in two different ways, making use either of drag or of lift. For example, ducks swim by spreading their webbed feet and moving them backward through the water. Drag on the backward-moving feet acts forward, providing the thrust that drives...

  18. Chapter Fifteen Swimming by Undulation
    (pp. 266-287)

    FIGURE 15.1 shows twelve stills from a film of a dogfish swimming. It is passing waves of bending backward along its body; dots on frames 3 to 8 mark successive positions of the crest of one of the waves. This action drives the fish forward. Many fishes and some snakes and worms swim in this way, by undulating their bodies. In addition, many fish and cephalopods swim by passing waves of bending along fins. This chapter is about swimming by undulation, both of the body as a whole and of fins separately.

    In Section 14.4 we considered the tails of...

  19. Chapter Sixteen Swimming by Jet Propulsion
    (pp. 288-300)

    THIS CHAPTER is about animals that propel themselves through water by squirting a jet of water out of a contracting cavity. They include squids and other cephalopods that drive water out of the mantle cavity by contraction of its muscular wall (Fig. 16.1A); a few bivalve molluscs, such as Pecten, that squirt jets of water out of their mantle cavities by adducting the valves of the shell (Fig. 16.1B); and medusae, which contract to expel water from the space enclosed by their bell. Other examples of jet-propelled swimmers include salps, which draw water in at the anterior end of the...

  20. Chapter Seventeen Buoyancy
    (pp. 301-315)

    FRESHWATER has a density of 1000 kg/m³, and seawater about 1026 kg/m³. Animals’ bodies consist largely of materials that are denser than either. For example, the muscles of fishes (both selachians and teleosts) have densities between about 1040 and 1080 kg/m³, and teleost guts have densities around 1040 kg/m³ (Alexander 1993b). The soft parts of Nautilus, removed from the shell, have a density of about 1060 kg/m³ (Denton and Gilpin-Brown 1973). Skeletal materials are generally denser, for example, 1060–1180 kg/m³ for selachian cartilage, 1300–2000 kg/m³ for teleost bone, and 2700 kg/m³ for mollusc shell (Alexander 1993b; Wainwright et...

  21. Chapter Eighteen Aids to Human Locomotion
    (pp. 316-326)

    UNLIKE ANIMALS, we humans make a great deal of use of manufactured aids to locomotion. We wear shoes. Scuba divers carry gas cylinders and wear fins on their feet. We ride bicycles and row boats. And we make a great deal of use of vehicles with engines, including cars, ships, and aircraft. It seems inappropriate to discuss engine-powered vehicles in this book, but it seems interesting to ask how devices that do not incorporate engines enable us to make more effective use of our own muscles. Why, for example, is it faster and less tiring to cycle than to run?...

  22. Chapter Nineteen Epilogue
    (pp. 327-332)

    SO FAR, I have discussed running, swimming, and flight separately. In this short concluding chapter I consider them together, and attempt some generalizations about locomotion. Dickinson et al. (2000) is a longer review with similar aims.

    The metabolic cost of transport is the metabolic energy cost of moving unit mass of animal unit distance. The gross cost is (Metabolic rate of moving animal)/(Body mass × Distance traveled). The net cost is (Metabolic rate of moving animal – Metabolic rate of stationary animal) / (Mass × Distance). Both are generally smaller for larger animals.

    For running, the net cost of transport...

  23. References
    (pp. 333-366)
  24. Index
    (pp. 367-372)