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.

PREFACE ix

Chapter 1: The Best Way to Travel 1


1.1. Fitness 1
1.2. Speed 2
1.3. Acceleration and Maneuverability 2
1.4. Endurance 4
1.5. Economy of Energy 7
1.6. Stability 8
1.7. Compromises 9
1.8. Constraints 9
1.9. Optimization Theory 10
1.10. Gaits 12


Chapter 2: Muscle, the Motor 15


2.1. How Muscles Exert Force 15
2.2. Shortening and Lengthening Muscle 22
2.3. Power Output of Muscles 26
2.4. Pennation Patterns and Moment Arms 28
2.5. Power Consumption 31
2.6. Some Other Types of Muscle 34


Chapter 3: Energy Requirements for Locomotion 38


3.1. Kinetic Energy 38
3.2. Gravitational Potential Energy 39
3.3. Elastic Strain Energy 40
3.4. Work That Does Not Increase the Body's Mechanical Energy 42
3.5. Work Requirements 46
3.6. Oscillatory Movements 48


Chapter 4: Consequences of Size Differences 53


4.1. Geometric Similarity, Allometry, and the Pace of Life 53
4.2. Dynamic Similarity 58
4.3. Elastic Similarity and Stress Similarity 60


Chapter 5: Methods for the Study of Locomotion 68


5.1. Cinematography and Video Recording 68
5.2. Stationary Locomotion 70
5.3. Measurement of Energy Consumption 73
5.4. Observing Flow 74
5.5. Forces and Pressures 76
5.6. Recording Muscle Action 80
5.7. Recording Movement at a Distance 83
5.8. Properties of Materials 84


Chapter 6: Alternative Techniques for Locomotion on Land 86


6.1. Two-Anchor Crawling 86
6.2. Crawling by Peristalsis 88
6.3. Serpentine Crawling 90
6.4. Froglike Hopping 91
6.5. An Inelastic Kangaroo 93
6.6. A Minimal Model of Walking 95
6.7. The Synthetic Wheel 97
6.8. Walkers with Heavy Legs 98
6.9. Spring-Mass Models of Running 99
6.10. Comparisons 100


Chapter 7: Walking, Running, and Hopping 103


7.1. Speed 103
7.2. Gaits 109
7.3. Forces and Energy 114
7.4. Energy-Saving Springs 122
7.5. Internal Kinetic Energy 125
7.6. Metabolic Cost of Transport 128
7.7. Prediction of Optimal Gaits 133
7.8. Soft Ground, Hills, and Loads 136
7.9. Stability 139
7.10. Maneuverability 143


Chapter 8: Climbing and Jumping 146


8.1. Standing Jumps 146
8.2. Leg Design and Jumping Technique 150
8.3. Size and Jumping 153
8.4. Jumping from Branches 155
8.5. Climbing Vertical Surfaces and Walking on the Ceiling 159


Chapter 9: Crawling and Burrowing 166


9.1. Worms 166
9.2. Insect Larvae 170
9.3. Molluscs 171
9.4. Reptiles 176
9.5. Mammals 179


Chapter 10: Gliding and Soaring 181


10.1. Drag 181
10.2. Lift 183
10.3. Drag on Aerofoils 187
10.4. Gliding Performance 192
10.5. Stability 200
10.6. Soaring 201


Chapter 11: Hovering 209


11.1. Airflow around Hovering Animals 209
11.2. Lift Generation 213
11.3. Power for Hovering 221


Chapter 12: Powered Forward Flight 224


12.1. Aerodynamics of Flapping Flight 224
12.2. Power Requirements for Flight 228
12.3. Optimization of Flight 236


Chapter 13: Moving on the Surface of Water 240


13.1. Fisher Spiders 240
13.2. Basilisk Lizards 244
13.3. Surface Swimmers 246


Chapter 14: Swimming with Oars and Hydrofoils 249


14.1. Froude Efficiency 249
14.2. Drag-Powered Swimming 250
14.3. Swimming Powered by Lift on Limbs or Paired Fins 255
14.4. Swimming with Hydrofoil Tails 261
14.5. Porpoising 264


Chapter 15: Swimming by Undulation 266


15.1. Undulating Fishes 266
15.2. Muscle Activity in Undulating Fishes 277
15.3. Fins, Tails, and Gaits 282
15.4. Undulating Worms 284


Chapter 16: Swimming by Jet Propulsion 288


16.1. Efficiency of Jet Propulsion 288
16.2. Elastic Mechanisms in Jet Propulsion 296


Chapter 17: Buoyancy 301


17.1. Buoyancy Organs 301
17.2. Swimming by Dense Animals 303
17.3. Energetics of Buoyancy 307
17.4. Buoyancy and Lifestyle 311


Chapter 18: Aids to Human Locomotion 316


18.1. Shoes 316
18.2. Bicycles 318
18.3. Scuba 321
18.4. Boats 322
18.5. Aircraft without Engines 324


Chapter 19: Epilogue 327


19.1. Metabolic Cost of Transport 327
19.2. Speeds 328
19.3. Gaits 330
19.4. Elastic Mechanisms 331
19.5. Priorities for Further Research 331


REFERENCES 333
INDEX 367