Fig. 1.

Cruising speed and the cost of transport as a function of body mass. (A) Cruising speed of fishes with RM endothermy (pink) and fishes without it (light blue) recorded in the wild, with other vertebrates swimmers [seabirds, marine mammals (gray), and sea turtles (black)] for comparison. (B) Cost of transport (i.e., the energy needed to move a unit body mass over a unit distance) estimated for each fish species with each cruising speed. See main text for the equations of phylogenetically informed regression lines shown in the figure, except for seabirds (speed = 1.60 × mass^0.04) and marine mammals (speed = 0.78 × mass^0.10) (21) in A.