The striped marlin is one of the largest and fastest predatory fish in the ocean. This species forms groups when hunting schools of small fish, aided by its long, spear-like rostrum. A study by the Cluster of Excellence “Science of Intelligence“ (SCIoI) with Humboldt-Universität zu Berlin and IGB now explains how the fish might coordinate the rapid sequence of their attacks without injuring each other. The key to this, they suggest, is rapid colour changes - like a traffic light. Bright body stripes signalise: "Now it's my turn to hunt".