Wave-generating Behavior: How Killer Whales Capture Seals on Ice Floes

Antarctic killer whales (Orcinus orca) hunt seals by cooperatively generating waves to break ice floes. Observations show they tilt bodies (head up) and slap tails downward, suggesting a link between swimming posture and wave generation. We conducted experiments in a towing tank to investigate the ice-breaking mechanism using an orca model with body pitch (10°/0°/-10°) and tail angles (30°/0°/-30°) at 0.3–0.7 m/s. Artificial ice floe units (hexagonal aluminum-polystyrene foam) were used. Results show that the optimal case—body 10°, tail -30°—produced the most pronounced trough waves. The wave depth was 1.3× deeper waves than suboptimal (-10°/-30°). Tail angle (despite being <1/5 body length) dominated flow structure. Surface flow visualization confirmed that the optimal case generated the highest curvature variation, subjecting the ice floe to prolonged bending stress until fracture. Only in this case did the artificial ice floe successfully break. Smaller ice fragments exhibited more pronounced tilting in the trough wave, with the wave’s trailing edge penetrating the ice surface. Force measurements on ice units revealed that the normal force exerted by the wave in the optimal case was over twice that of other cases. However, when larger ice floes obstructed the wave path, energy dissipation weakened the normal force, explaining why orcas prefer breaking ice in open waters. These findings may aid unmanned ice-breaking vehicle design. The mechanism could inspire swarm-based underwater systems.