One porcupine in roughly every max(2, 8 − 5·transmission) takes a sentinel role and periodically scans for danger. Each sentinel's scan phase follows sin(0.6·t + φ); when it crosses a threshold that tightens as predator risk rises, it fires a quill-flare alert.
- Alert ripple — every alert emits an expanding ring; group members it sweeps over pull toward the den, scaled by signal transmission — weak transmission means the warning barely spreads, strong transmission pulls the whole group in.
- Cohesion —
clamp(105 − spread/n·8, 18, 99), where spread is the average distance from each porcupine to the group centroid.
- Density — population divided by the occupied area, so a tighter or larger group changes it directly.