Can “pingers” and Other Acoustic Warnings Mitigate Collision Risks Between Boats and Cetaceans?

[Un article de The Conversation écrit par Charlotte Curé – Directrice de recherche en Bioacoustique à l’UMRAE, Cerema ; Isabelle Charrier – Chercheuse CNRS en bioacoustique, Université Paris-Saclay ; Loanne Pichot – Doctorante en bioacoustique, Université Gustave Eiffel ; et Olivier Adam – Bioacousticien, Sorbonne Université]

This year, the organization of the Vendée Globe asked competitors to avoid protected areas to reduce the risk of collisions with cetaceans – large sperm whales, including gray whales. Some boats are even equipped with “pingers”, sound scaling devices that aim to keep animals away from ships. Already used by certain fishing boats, especially in the Gulf of Gascogne to avoid accidental catches of cetaceans in the nets, their use in the prevention of collisions between ships and cetaceans is less documented.

Currently, the efficiency of Pingers has not been demonstrated by research. If the idea may seem good, it raises different questions. Wouldn't the Pingers represent a new form of human “pressure” for cetaceans? Do the 90 species all react there in the same way? Could animals get used to these “ping” underwater sounds over time, de facto reducing their effectiveness in scareing them?

Used in combination with other maritime traffic management measures – speed limitation in areas of high abundance of cetaceans for example – and optimized to limit their harmful imprint on animals and the marine environment, pingers could help Reducing collisions between ships and cetaceans, which kill thousands of cetaceans each year and which are responsible for almost 30 % of deaths in certain endangered species, such as the black whale of the North Atlantic.

How collisions are avoided today

The risk of collisions is amplified in areas of high density of cetaceans and significant maritime traffic. Beyond fatal accidents, collisions lead to serious injuries, stress and behavioral disturbances which all participate in the global decline of cetacean populations.

To avoid them, in addition to bypassing measures of protected areas and reduction of the speed of ships, it is necessary to develop immediate solutions such as the training of captains and staff aboard the merchant navy, and continue to develop new technologies as Visual and acoustic detection tools in real time.

In addition, scientific studies also make it possible to identify sensitive areas, at high risk of collision.

Ambient noise can prevent whales from hearing a ship as approaching

While acoustics is the predilection sensory modality used in the life of cetaceans, the underwater hubbub generated by human activities-whose maritime traffic-partly masks sounds produced by these marine mammals. This decreases their capacities to communicate with their fellows, find their prey, detect the presence of predators, and identify other dangers, such as a ship as approaching. For example, bastard whales have a low frequency auditory sensitivity 3 p.m.-20khz, corresponding overall to our hearing band but with better performance in infrasound-these performances must normally allow them to hear large ships.

Despite this, it seems that these large cetaceans have difficulty detecting and anticipating the approach of a ship and that they fail to avoid it. We see several reasons for it.

In an area of ​​strong maritime traffic, the ability to detect a ship among the noise of others is reduced. But other factors seem to worsen the problem, and in particular the speed of circulation of ships, much higher than that of these large whales. The displacement of humpback whales in their reproduction area, for example, is done on average at 2 knots. Not to mention the time they spend in a static position, as during the rest phases.

In addition, the variation in the properties of acoustic propagation in the water column (especially close to the surface) and the directionality of the noise of the boats (rather oriented towards the stern) could make the location of the ship difficult, and a potential habituration Continuous noise in maritime traffic could reduce the vigilance of whales as ships are approached.

In a desire to reduce the noise pollution generated by human activity at sea, the development of increasingly silent boats aims to reduce the impact of noise … But one can wonder if it is not, in an unhappy Side effect, increase the risk of non -detection of ships by whales and therefore collisions.

This is how the idea of ​​using “pingers”: devices emit repetition or warning signals for animals, initially designed to prevent accidental captures of cetaceans in the fishing nets in the fishing nets in the fishing nets And more recently offered as potential preventive measure to keep animals away from areas at high risk of impact such as wind sites for example, or to reduce collisions with ships.

In the latter case, the panger would be deployed on the shell of ships or on buoys in areas of high maritime circulation; It would generate a sound signal to scare the animals or alert them from the presence of a ship, then encouraging them to change direction before a collision occurred. These pingers could be activated remotely or automatically when a ship enters a proven risk area, identified by the maritime authorities.

We lack data to find out if the pingers are effective in avoiding collisions

The considerable lack of research aimed at experimentally testing the effectiveness of pingers does not allow today to decide on the relevance of their use.

Considered by some as horns that add noise to the ambient noise, or as a miracle solution by others, the use of pingers and other warning sound devices is subject to debates.

If some encouraging scientific results have been obtained (modification of the trajectory of cetaceans by moving away from the ship), others have not detected any beneficial effect or even sometimes an increase in the risk of collision (attraction to the sound source, suddenly raised cetacean on the surface).

Questions also remain as to their environmental impact, noise having potentially harmful effects in many species – with repercussions on the scale of ecosystems, and their implementation on a large scale.

Put very (too) early on the market, the Pingers have not been sufficiently tests to experimentally demonstrate their effectiveness. In addition, they are often made and used in a generic way while their conception should be thought almost on a case -by -case basis, depending on the hearing sensitivity of the targeted species, its behavior, the ecological context (food areas, of reproduction) and social (presence of young people, size of the group), properties of propagation of sound in the environment and natural and anthropogenic environmental pressures (level and bandwidth of ambient noise). From a scientific point of view, it seems that a universal sound warning for all cetacean species is difficult to conceive.

One of the tracks to improve the efficiency of pingers while limiting their impact would be to replace or combine synthetic signals classically used for natural signals (such as sounds produced by the species itself), potentially more informative And with fewer imprints on the environment. This requires upstream a lot of research to decipher the acoustic communication systems of the different cetacean species.

We are currently carrying out in partnership with the Greenov company a pilot study to test experimentally, in the field, the alert power of a sound signal among the humpback whales in a reproduction area, upstream of the development by the 'Company of a sound warning prototype to be fixed on the ship of ships. These experiences at sea are complex and require strict protocols that must be led by scientific experts. For this, we carry out experiences of commonly controlled sound exposure called ” playback », And let's measure the behavioral responses of humpback whales provided beforehand of multicaptive beacons deployed on their backs in a non -invasive manner by means of suction cups.

The United Nations Conference on the Oceans to be held in Nice from June 9 to 13, 2025, followed by the conference on collisions between ships and cetaceans on June 16, 2025 in Brest, will be two opportunities to bring together the actors of the maritime authorities, engineers And scientists, to collectively discuss the priorities of research to be carried out, and the solutions and regulatory measures to be adopted.