Cada año, más de 60,000 ships cross the Strait of Gibraltar, a strategic point that connects the Atlantic with the Mediterranean and supports a large part of global trade. Beneath this surface lives a critical population of just 250 long-finned pilot whales (Globicephala melas), categorized as endangered.
For these social cetaceans, daily life has become an exercise in survival: they must dodge vessels while searching for food, coordinating group movements, and raising their young. The biggest obstacle is not physical but auditory.
The scientific study
An international team led by Milou Hegeman and Frants Jensen from Aarhus University documented that pilot whales are increasing the volume of their vocalizations to be heard over the noise of maritime traffic.
The work, published in Journal of Experimental Biology, analyzed more than 1,400 calls recorded between 2012 and 2015 using sensors attached with suction cups to the backs of 23 pilot whales. These recordings allowed the classification of vocalizations into four types:
- Low-frequency calls.
- Short and pulsed calls.
- High-frequency calls.
- Two-component calls.
The most important for group cohesion—low frequency and two-component—have already reached their physiological limit: “they cannot shout any louder”, warns the study.
The impact of noise
Acoustic levels in the Strait range from 79 to 144 decibels, comparable to the noise of a crowded restaurant or the roar of a nearby vacuum cleaner. In this context, long-finned pilot whales try to adapt, but long-range calls lose effectiveness.
The failure in communication is not a minor detail: these signals are essential for reuniting after long dives. If they do not reach, the group fragments, compromising coordination, hunting, and reproduction. With only 250 individuals, any alteration in social cohesion can be critical.
A global problem
Marine acoustic pollution is an invisible impact: it leaves no stains or residues, but it profoundly alters the lives of species that depend on sound to survive. According to Michel André from the Polytechnic University of Catalonia, noise affects all links in the food chain, from phytoplankton to cetaceans.
The case of the Strait of Gibraltar is paradigmatic: the sea is no longer a natural resonance space but a saturated environment where each message competes with the constant roar of engines.
Mitigation measures
Specialists warn that reducing noise is not an aesthetic option but a vital necessity. Some proposals include:
- Alternative maritime routes to decrease pressure on critical areas.
- Quieter engine technologies to reduce acoustic pollution.
- Acoustic exclusion zones where vessel traffic is limited.
- Greater international awareness about the importance of sound in marine life.
The long-finned pilot whales of the Strait are pushing their vocal capacity to the limit to survive in an environment dominated by maritime traffic. Reducing noise can make the difference between the survival of this critical population or their silent disappearance. The challenge is global: if the sea ceases to be a space for communication, many species will lose the basic tool that allows them to exist.
