For whales and dolphins, sound is their lifeline. In the dim underwater world where sight is limited, these marine mammals rely on sound to communicate, find food and navigate vast distances. A blue whale’s deep, rumbling calls can travel thousands of kilometres.
But the ocean’s natural soundscape is changing. Human noise is now one of the biggest threats facing whales and dolphins, experts at Whale and Dolphin Conservation explain.
What is underwater noise pollution?
‘Anthropogenic’ (human-made) noise pollution refers to any sound that disrupts the ocean’s natural acoustic environment. The main culprits include:
- Pile driving and construction: The installation of wind turbines and coastal infrastructure sends loud, impulsive sounds through the seabed.
- Shipping traffic: Large vessels produce a constant, low-frequency hum that can travel for miles underwater.
- Sonar and seismic surveys: Used by the military and energy industries, these loud pulses can travel hundreds of kilometres through the sea.
Why are whales and dolphins so sensitive to noise pollution?
Unlike humans, whales and dolphins depend on sound as their primary sense. Through a process called echolocation, they send out clicks and listen for echoes to communicate and experience the world around them. It’s how they hunt, navigate and stay in touch with their pod.
When the ocean fills with artificial noise, these sounds can be drowned out or distorted. This has the effect of masking communication, disrupting feeding and disorienting animals that rely entirely on hearing to survive.
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The physical harm of noise pollution
Loud or prolonged noise doesn’t just interfere with behaviour – it can cause real physical harm. Powerful naval sonar has been linked to mass strandings, such as the 2013 event off Cornwall where dozens of common dolphins came ashore.
Noise can also elevate stress levels, suppress immune systems and affect breeding success in species such as the critically endangered North Atlantic right whale.
Migratory impacts of noise pollution for underwater animals
When an area becomes too noisy, whales and dolphins often abandon it altogether. From the Arctic to the Pacific, researchers have documented species avoiding key feeding and breeding grounds due to rising noise levels. These changes can alter migration routes and reduce access to food, with consequences for entire populations.
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What's being done to prevent underwater noise pollution and its impacts?
Awareness of underwater noise pollution is growing, and with it, new solutions. Shipping companies are developing quieter propellers and hulls, naval forces are trialling less harmful sonar, and wind farm developers are using 'bubble curtains' to dampen construction noise. International efforts, including guidelines from the International Maritime Organisation, are encouraging the adoption of 'quieting technologies'.
Researchers are also identifying 'acoustic sanctuaries' – areas where marine life can thrive in relative peace and quiet.
Top image credit: Getty Images
