Pilot whales in the Strait of Gibraltar are losing the ability to hear each other. The constant roar of passing ships is drowning out their calls, according to a new study. Researchers found that vessel noise reduces the whales' communication range by up to 80 percent, leaving them unable to stay in touch with their pods.
A narrow sea lane packed with ships
The Strait of Gibraltar is a narrow waterway between Spain and Morocco. It connects the Atlantic Ocean to the Mediterranean Sea. Every day, hundreds of cargo ships, tankers, and ferries squeeze through this 14 kilometer wide channel. For the long finned pilot whales that live there, this means a constant wall of underwater noise.
Scientists from the University of St Andrews and the Spanish conservation group CIRCE attached temporary tags to 10 pilot whales. The tags recorded both the sounds the whales made and the noise around them. The team also used hydrophones to listen to the overall soundscape of the strait.
How loud is too loud for a whale
Pilot whales rely on sound to navigate, find food, and stay connected with their group. They produce short, clicking calls and longer whistles. But the study showed that ship noise overlaps almost perfectly with the frequencies the whales use to communicate.
When a large vessel passed within a few kilometers, the background noise jumped so high that a whale's call could only be heard by another whale less than 100 meters away. In quiet conditions, those same calls would travel more than a kilometer. The whales did try to adapt. They called louder and repeated themselves more often. But even then, their effective communication range shrank by roughly half.
Why local conservationists are concerned
Only about 200 long finned pilot whales remain in the Strait of Gibraltar. They are already listed as vulnerable by the IUCN. The population is isolated and faces threats from fishing nets, pollution, and now, lost contact with each other.
Local people in the coastal towns of Tarifa and Algeciras depend on whale watching tourism. They have watched these animals for generations. Conservationists worry that if the whales cannot hear each other, they may struggle to coordinate hunting or keep families together. The study did not prove that whales are abandoning their pods, but it showed that the noise is severe enough to make normal social calls useless.
A sound that never stops
The researchers measured noise levels over several months. They found that commercial shipping created a near constant low hum. Even at night, when some ships slow down, the noise did not drop enough for the whales to communicate freely. The busiest shipping lanes cut directly through the area where the whales feed and socialize.
The study was published in the journal Marine Pollution Bulletin. It adds to a growing body of evidence that ocean noise pollution is not just an annoyance for marine life. It can physically cut animals off from one another. In a narrow strait with heavy traffic, there is no quiet place to go.
