ALEXANDER, R McN: Merits and Implications of Travel by Swimming, Flight and Running for Animals of Different Sizes

Many measurements have been published of metabolic rates of animals walking, swimming or flying at different speeds. These have been used to derive allometric equations predicting the optimum speed and the metabolic rate at that speed for animals of different sizes, for each mode of locomotion. Flapping flight is by far the fastest means of travel, but also requires much the highest metabolic rates. Endothermic swimmers such as penguins and seals have much higher maximum range speeds than ectothermic swimmers, a consequence of their higher resting metabolic rates. The possible benefits of migration, for animals using each style of locomotion, are assessed by balancing the time and energy costs of the journey against the rate at which energy stores can be accumulated in a favourable habitat. Annual migrations of a thousand kilometres or more are unlikely to be beneficial for small walkers or swimmers. Very long migrations are practicable only for flying animals and for very large endothermic swimmers. The implications for central place foraging, of the speeds and energy costs of different modes of locomotion, are also discussed.