Fig. 5. Structural stiffness and stiffness constants for an ontogenetic series of dolphins. Values are shown for deformation in the lateral (mean value for both left and right), dorsal and ventral directions. Vertical dotted lines distinguish different life-history stages. (A) Structural stiffness was calculated for deformations that were less than 10% of total body length and thus often represent single data points. For dorsal and ventral deformations, the average standard deviation was 7.5 and 0.8, respectively. For lateral deformations, the average standard deviation was 9.8. Fetal deformations typically exceeded the stated criterion, even with loads that were too small to be measured with our apparatus. For these animals, we assumed a load of 0.98 N and used the resultant deformations. Thus, these values should be considered approximations. (B) Stiffness constant (k) for an ontogenetic series of dolphins. Values were calculated for all deformations that exceeded 10% of total body length.