Figure 8. Relationship between the digging activity, measured as the excavated volume (x-axis), and the excavated shape, expressed as the form factor (y-axis).

(a) Experiment 5: brood only series. Closed circles: brood; y = 1E-6x+0.387; open circles: no brood (empty tunnel); y = 1E-07x+0.523. (b) Experiment 6: brood and fungus series. Closed circles: brood and fungus; y = 5E-07x+0.689; open circles: fungus; y = 2E-06x+0.425; y-axis starts from a baseline form factor of 0.28.