Predatory trumpetfish conceal themselves from their prey by swimming alongside other fish

Many animals use camouflage to avoid detection by others, yet even the most inconspicuous objects become detectable against the background when moving^1,2. One way to reduce detection while moving would be to 'hide' behind the movements of objects or other animals³. Here, we demonstrate experimentally that a common marine predator, the trumpetfish (Aulostomus maculatus), can conceal its approach from its prey by performing a behaviour known as 'shadowing' - swimming closely next to another, larger and non-predatory fish^3,4,5. Our findings reveal how predators can actively use another animal as a form of concealment to reduce detection by prey.