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A scatterplot with two logarithmic axes, plotting the weight of an animal or mode of transport on the y axis and the energy cost of transport in calories per gram per kilometer on the x axis. There is a general downward trend, i.e. heavier animals or modes of transport are more efficient, with a few notable outliers: Small mammals like mice and lemmings are very inefficient for their size, helicopters are very inefficient for their size, while salmons and even more so humans on bicycles are very efficient for their size. The plot is captioned: MAN ON A BICYCLE ranks first in efficiency among traveling animals and machines in terms of energy consumed in moving a certain distance as a function of body weight. The rate of energy consumption for a bicyclist (about .15 calorie per gram per kilometer) is approximately a fifth of that for an unaided walking man (about .75 calorie per gram per kilometer). With the exception of the black point representing the bicyclist (lower right), this graph is based on data originally compiled by Vance A. Tucker of Duke University.