Ship Noise Inhibits Colour Change, Camouflage, and Anti-Predator Behaviour in Shore Crabs

The marine environment is experiencing unprecedented levels of anthropogenic noise. This is known to have adverse effects across a range of taxa, directly affecting sensory systems and behaviours. Stress caused by noise pollution may affect physiological processes that do not have obvious links to the acoustic environment. We show that noise from shipping reduces colour change and consequent camouflage in juvenile shore crabs (Carcinus maenas). Furthermore, ship noise causes maladaptive defensive responses, with crabs less likely to flee a simulated predator attack. In contrast, loud natural noises at the same intensity have none of the same negative effects. Our study shows that anthropogenic noise is likely to be more disruptive than anticipated. Its effects are not confined to species that are reliant upon auditory communication, and may be more severe than would be predicted based only on the amplitude of the sound.