MOVING CHEAPLY - ENERGETICS OF WALKING IN THE AFRICAN ELEPHANT

Large animals have a much better fuel economy than small ones, both wh en they rest and when they run. At rest, each gram of tissue of the la rgest land animal, the African elephant, consumes metabolic energy at 1/20 the rate of a mouse; using existing allometric relationships, we calculate that it should be able to carry Ig of its tissue (or a load) for 1km at 1/40 the cost for a mouse. These relationships between ene rgetics and size are so consistent that they have been characterized a s biological laws. The elephant has massive legs and lumbers along awk wardly, suggesting that it might expend more energy to move about than other animals. We find, however, that its energetic cost of locomotio n is predicted remarkably well by the allometric relationships and is the lowest recorded for any living land animal.