Fig. 7. Relationships based on theoretical calculations for a seal pup with a total volume of 100 litres. (A) Buoyant force attributed to different body components. The broken blue line represents the buoyant force (negative) of the total non-lipid body, while the red line represents the buoyant force of the whole body, including lipid but assuming no residual air. The broken black lines represent the buoyant force of the total body, including residual air left in the lungs at 10 m-depth intervals from 10 m to 50 m. (B) Drift rates predicted from equation 9 for the 100-litre seal, assuming a total surface area of 1 m². The red line represents the drift rate assuming no residual air in the lungs, while the broken black lines represent drift rate accounting for residual air at 10 m intervals from 10 m to 100 m. (C) Drift rate calculated from equation 9, assuming no residual air in the lungs. The red line represents drift rate assuming a surface area of 1 m² (i.e. identical to the red line in B), while the broken black lines represent the drift rate resulting from variations in surface area. The two extreme values of surface area, 0.5 m² and 1.5 m², are indicated by the blue and green lines, respectively. (D) Drift rates calculated from equation 9 using the minimum and maximum seawater densities (1.027 g cm^-3 and 1.030 g cm^-3; blue and green curve, respectively) likely to be encountered by southern elephant seal pups from Macquarie Island. See text for further details.