Anthropogenic noise from shipping, sonar, and seismic surveys has transformed the underwater acoustic environment, causing welfare harm to marine mammals that depend on sound for navigation and communication.
Marine mammals evolved in an ocean where biological sounds dominated — whale song, dolphin clicks, seal calls. The transformation of the underwater acoustic environment by human industry has created a world many marine mammals can barely navigate. Whales that communicate over hundreds of kilometers are drowned out by shipping noise. Dolphins using echolocation for hunting find their signals masked. The chronic stress response from acoustic overstimulation is measurable in cortisol levels and behavioral changes in populations subject to high noise exposure. Acute sonar exposure that causes disorientation and stranding represents the most visible welfare harm, but chronic noise degradation may represent a larger cumulative welfare burden.