Table 4.
Results: summary of scaling factors (b) obtained for fore- and hindpads from mechanically tested specimens. A, y and ky were obtained empirically (n = 10 subjects) and the scaling factors reported here are RMA slopes; values for the rest of the variables are derived in the same way they were for the hypotheses (see table 2 and see the electronic supplementary material, §1). All variables (except A and y) are calculated under the load to which the pad is subjected when the animal is standing.
| mechanically tested specimens (n = 10 subjects) |
area (bA)a | thickness (by)a | stiffness (bky) | foot pressure (bP) | Young's modulus (bEy) | strain (bεy) | deformation (bΔy) | strain energy density (bu) | strain energy storage (bU) | |
|---|---|---|---|---|---|---|---|---|---|---|
| fore | b (s.e.) | 1.05 (0.12) | 0.06 | 0.59 | −0.53 | −0.05 | −0.47 | 0.95 | ||
| 95% CI | 0.78–1.31e | |||||||||
| r2 | 0.90 | |||||||||
| fore and hinda | b (s.e.) | 0.94 (0.22) | 0.48b (0.06) | |||||||
| 95% CI | 0.44–1.44 | 0.34–0.63 | ||||||||
| r2 | 0.56c; 0.86d | 0.87 | ||||||||
| hind | b (s.e.) | 0.85 (0.11) | 0.06 | 0.39 | −0.33 | 0.15 | −0.27 | 1.15 | ||
| 95% CI | 0.59–1.10e | |||||||||
| r2 | 0.86 | |||||||||
aEstimates of bky for fore- and hindpads differ significantly (p = 0.04), but fore- and hindpads do not differ for bA (p = 0.10; n = 10 subjects) or by (p = 0.32; n = 9 subjects because hindpad thickness data for hyena were unavailable). In calculations of b for the other mechanical parameters, total area of m-p pads was used for estimates of bA, average of fore and hind thicknesses was used for estimates of by, and separate estimates of bky were used for fore- and hindpads.
bn = 10 subjects; forepad thickness of hyena was used in place of average of fore + hind in calculating this by.
cIn the sample of n = 10 mechanically tested subjects the correlation of log A with log M is relatively low.
dThe value of r2 for log A and log M rises dramatically if the clouded leopard, which has relatively large feet, is removed, leaving n = 9. By contrast, removal of the clouded leopard changes r2 for by and bky by at most 0.01 (not shown here). For alternative estimates of bA and its CIs for this sample, see the electronic supplementary material, table S1.1 and figure S1.1.
eThese RMA CIs were obtained by calculation; for CIs obtained by bootstrap or for phylogenetically independent contrasts see the electronic supplementary material, table S1.3.