An instructor from the Cercle de la Voile de Dieppe was sailing along the coast with trainees on the morning of Sunday 23 August 2026. Near the harbour, the boat had to wait for the ferry to leave. That is when several dolphins joined it, circled around it, then came and struck the rudder blade several times over. The club alerted the French Navy signal station and published a warning notice to recreational boaters on the Facebook page La Plaisance à Dieppe. The behaviour is commonplace among the killer whales of the Strait of Gibraltar. It is almost unknown among dolphins.
What happened
| Date | Sunday 23 August 2026, in the morning |
|---|---|
| Location | Off Dieppe (Seine-Maritime), near the harbour, waiting for the ferry to leave |
| Boat | Sailing boat of the Cercle de la Voile de Dieppe, one instructor and trainees on a training exercise |
| Animals | Several dolphins, identified as common bottlenose dolphins by Le Télégramme |
| Behaviour | Circling the hull, then repeated blows to the rudder blade |
| Damage | None reported |
| Follow-up | Alert to the French Navy signal station, warning notice published on Facebook |
The rudder blade, and why that detail decides everything
The rudder blade is the movable blade of the steering gear, under the hull. It deflects the flow of water and gives the boat its direction. Damaged, it leaves the sailing boat unable to steer, which turns a curiosity into a question of safety.
That detail is what makes the episode remarkable. A cetacean that accompanies a bow, that rides a boat’s wave, that circles a hull, is ordinary and documented in our catalogue of aquatic behaviours. A cetacean that comes and strikes one specific moving part, below the waterline, several times over, is not. The rudder blade is the only part of a sailing boat that moves, that vibrates and that returns a different signal to sonar. It is also, very precisely, what the Iberian killer whales have been targeting since May 2020.
Why the comparison is legitimate
The two scientists quoted in the press draw the same comparison, with the same caution. For Maïlys Baudoint, in charge of citizen science at the Groupe d’Étude des Cétacés du Cotentin, “these behaviours could be compared with what is happening in the Strait of Gibraltar with the killer whales”, because “cetaceans are very social animals and they operate in groups. So they pass behaviours on to one another”. For Willy Dabin, of the Pelagis observatory, this is a “very rare and strange phenomenon”, but one that “would look more like play”, the behaviours being transmitted “by social imitation and group learning”.
What these two readings share is solid. Delphinids learn from one another, and behavioural innovations have spread through entire groups within a few years, from sponging among the Shark Bay dolphins to the fashion for salmon “hats” among the killer whales of the north-east Pacific. A new habit in one individual can become a habit of the group. That is the hypothesis adopted at Gibraltar, set out in our page Why do killer whales attack boats?.
Where the comparison stops
The comparison stops fairly quickly, and it is better to say so plainly.
| Iberian killer whales | Dieppe, 23 August 2026 | |
|---|---|---|
| Number of episodes | More than 700 since May 2020 | 1 |
| Mass of the animal | Up to 5 tonnes | A few hundred kilos, for 2 to 4 metres |
| Damage | Rudders destroyed, several sailing boats sunk | None reported |
| Population concerned | 37 individuals, monitored one by one | Unknown, animals not identified |
| Origin of the behaviour | Attributed to one female, then spread | Unknown |
There is a difference in kind, and not only in degree. At Gibraltar, we are talking about a behaviour that is documented, repeated, mapped and dated, in a fully catalogued population. At Dieppe, we are talking about one morning. The comparison is legitimate as a working hypothesis. It is not legitimate as a conclusion, and neither of the two researchers quoted presents it otherwise. As actu.fr points out, “no scientific explanation exists, only hypotheses”.
Which species, exactly
The club’s post takes care to specify that these were not harbour porpoises but indeed dolphins, which is already a careful and useful identification. Le Télégramme goes further and speaks of common bottlenose dolphins, Tursiops truncatus, two to four metres long.
That is the most likely hypothesis, and for a precise reason. The English Channel holds one of the largest resident coastal populations on the European Atlantic seaboard, monitored since 1997 by the Groupe d’Étude des Cétacés du Cotentin. The 2023 monitoring report, produced for the Office français de la biodiversité, describes a population that is genetically isolated and broadly stable since 2010, known individual by individual thanks to photo-identification of dorsal fins: close to 6,500 usable photographs and 2,886 dorsal fins analysed for the year 2023 alone.
In other words, these animals are not anonymous. In this region, a dolphin photographed in profile is often an identifiable dolphin, with a history, earlier encounters and a catalogue number.
The video that was not released
The scene was filmed. The author of the post explains that he cannot release the video because it shows the trainees and he does not hold their image rights. The decision is the right one, and it should be said without reservation: the image rights of people in training, some of them minors, come before documentary interest.
It remains that this video is, to date, the only material evidence of the episode. It would make it possible to count the animals, to estimate their size, to tell a blow from the rostrum apart from a rub, and above all to read the dorsal fins. None of that is possible from an account. This is not a reproach to the club, which did what was needed by alerting the signal station and warning other boaters. It is a point of method: between publication to the general public and disappearance, there is a middle path, which consists in passing the images on to the monitoring teams, on condition of scientific use and without release. The GECC runs ObsenMer, a citizen science platform where sightings are recorded and then validated, and which also serves as a photo-identification database for its own surveys. We list these schemes in our page on citizen science programmes.
Two sets of advice, and the nuance between them
The two specialists give similar instructions, and it is worth placing them side by side.
| Maïlys Baudoint (GECC) | Keep your distance, hold your course, do not change your heading |
|---|---|
| Willy Dabin (Pelagis) | Keep a distance, let the animals come to you, do not deliberately drive at the group, do not change course, cut the engines |
The substance is identical: do not pursue, do not manoeuvre in order to follow the animals, do not cut across them. The only apparent difference concerns the engines, and it dissolves as soon as the context is spelled out. Cutting the propeller removes the risk of injury, which is the real danger in a close encounter, and it reduces noise. Holding your course means not starting to zigzag in order to stay with the group, and not swerving to avoid it at the last moment. A sailing boat that cuts its engine and carries on under sail applies both instructions at once.
On whether the behaviour is dangerous to people, the two answers also agree. The animals “were really interested in the rudder blade and not at all in the humans”, notes Maïlys Baudoint. They have, according to Willy Dabin, “on the face of it, no bad intentions or aggressive actions towards humans”. The risk, if there is one, is a risk to equipment, therefore to manoeuvrability, therefore to navigation.
One week, two scenes, and a trap in reading them
Two days after Dieppe, on the evening of Tuesday 25 August, off Sanary-sur-Mer, the passengers of the Croix du Sud V witnessed another rare scene: some forty pilot whales harried four sperm whales for half an hour. Tail blows on both sides, a defensive marguerite formation among the sperm whales, intense production of bubbles to disrupt echolocation. The confrontation ended against the hull of the boat, which had been left drifting with its engines off. The crew is still wondering whether the sperm whales were trying to use the vessel as a shield.
It is tempting to read a series into this. That is the trap. Two rare scenes in the same week, on two seaboards a thousand kilometres apart, between different species and in contexts that have nothing in common, remain two rare scenes. The number of observers at sea is at its highest at the end of August, phones film everything, and an episode that would have been told at the harbour bar twenty years ago now makes three articles. A rise in reports is not a rise in events for as long as the survey effort is unknown, which we set out in our sighting data for France.
That does not mean there is nothing there. Maïlys Baudoint notes, moreover, that “we are starting to get several reports”, and this is exactly the situation in which one should collect rather than conclude. The Gibraltar behaviour was not identified on a single episode either: it was identified on an accumulation of accounts that someone took the trouble to compile.
If this happens to you
- Cut the engine, hold your course, do not manoeuvre to follow or to avoid the animals at the last moment.
- Do not enter the water, do not try to push an animal away, do not touch.
- Note the time, the position, the number of animals, the duration, and exactly what they went for.
- Film if that is possible without putting the crew in danger, and keep the images even if they cannot be released: the dorsal fin is worth an identification.
- Report the sighting on ObsenMer, and alert the signal station if the boat’s manoeuvrability is affected.
- Check the rudder blade and the steering gear before setting off again, even with no visible damage.
These reflexes apply beyond this particular case, and they meet what we bring together in How to prepare for your whale watching trip and in our overview of the marine mammals of France.
What it would take to settle the question
Three elements are missing, and all three are within reach. The first is identification of the animals: the English Channel is one of the few areas in Europe where that question has a possible answer, catalogue in hand. The second is a count of reports set against effort at sea, without which we shall never know whether the phenomenon is increasing or whether it is the attention that is increasing. The third is a fine-grained description of the behaviour: a dolphin rubbing its flank against a rudder blade and a dolphin striking it with its rostrum do not tell the same story, and only images make it possible to tell them apart.
In the meantime, the most accurate wording remains Willy Dabin’s: a rare and strange phenomenon. Neither an attack nor an anecdote.
Sources: post on the Facebook page La Plaisance à Dieppe; Jean-François Caru, « Ils venaient taper le safran » : des dauphins percutent volontairement un voilier au large de Dieppe, actu.fr, 28 August 2026, with the comments of Maïlys Baudoint (GECC); Le Télégramme, Bateaux de plaisance percutés : après les orques, les dauphins s’y mettent aussi ?, 29 August 2026, with the comments of Willy Dabin (Pelagis observatory); Luc Mikailoff, Var actu, 27 August 2026, for the Sanary-sur-Mer episode; OFB / GECC scientific report on the 2023 monitoring of coastal common bottlenose dolphin populations of the Eastern Channel – North Sea and Western Channel – Celtic Seas marine sub-regions (agreement OFB-22-0749).
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