The forces on the calf calculated from equations (2) and (3). Definitions of the parameters appear in Figure 4. (a) The non-dimensional peak longitudinal force Xmax (thrust) on the calf as a function of the normalized lateral distance η/L1 from the mother, for different mother/calf size ratios (as indicated by the numbered arrows). The dashed red line indicates closest probable proximity. The ratios relevant here are from 1 (fully grown calf - the solid blue line) to 2 (neonate). (b) The non-dimensional peak lateral force on the calf, for different mother/calf size ratios, as a function of the normalized lateral distance η/L1 from the mother. The peak lateral force is obtained when the centers of mass of mother and calf are on a line perpendicular to the long axis (ξ = 0 in Figure 4). The curve marked 'wall effect' describes the lateral force on the calf when moving close to a wall, as in a tank. (c) The variation of forces and moments as one animal is placed at different normalized longitudinal positions relative to the other in the fore-aft direction. Positive values on the horizontal axis indicate that the mother's center is ahead of the calf. The lateral distance is one quarter of the calf's length. The curves marked X are the non-dimensional longitudinal force and Y is the normalized lateral (Bernoulli) force. Positive values indicate forward force and attraction, respectively, while negative values represent backward forces and repulsion, respectively. Two sets of curves are shown, for neonate calves (where the mother is twice as long; in solid blue), and for equal-sized animals (fully grown calf; dashed red line).
Weihs Journal of Biology 2004 3:8 doi:10.1186/jbiol2