The killer whale’s white patches: the study said to have solved their mystery does not exist

It is one of the most recognisable patterns in the animal world: two white ovals set on either side of the black head of the killer whale. A wave of articles has recently claimed that science has at last solved their mystery. We looked for the corresponding publication. It does not exist. That does not mean nothing is known: it means that what is known is more modest, and more interesting, than what is being said about it.

A check that takes only a few minutes

The search is reproducible. In Europe PMC, a database that indexes most of the biomedical and ecological literature, combining the terms killer whale and disruptive coloration returns zero results. Queries on killer whale pigmentation bring up no recent work devoted to the function of these patches.

The French text in fact carries its own answer, in small print: “article originally published on 10 August 2025”. It was brought forward again a year later under a headline announcing a breakthrough. And the two references it cites date from neither 2025 nor 2026.

Similä T. and Ugarte F.	1993, Canadian Journal of Zoology: observations of cooperative hunting by killer whales in northern Norway, description of the carousel technique
Mäkeläinen P., Esteban R., Foote A. and Kuningas S.	2014, Journal of the Marine Biological Association of the UK: comparison of pigmentation features among North Atlantic killer whale populations
English-language popular science article	July 2025, with no new research
French republication	published on 10 August 2025, brought forward again on 13 August 2026 under a headline announcing a discovery

An honest explanatory piece, resting on work from 1993 and 2014, thus became a scientific breakthrough through its packaging alone. The body of the article is not in fact bad: it is the headline and the republication that mislead.

First, it is not the eye

The most widespread confusion is anatomical. The white patch is not the eye and does not surround it. The killer whale’s eye is small, dark, and sits forward of and slightly below the patch, at the junction between the jaw and the rest of the head.

The patch itself is described as postocular: it develops behind the eye, on the side of the head. It is part of a wider pigmentation pattern that also includes the white belly, the grey saddle behind the dorsal fin, and the dark cape. Our page on pigmentation variation in cetaceans places this pattern among the others, and our interactive anatomy makes it possible to locate it.

In passing, a confusion of vocabulary to correct

Several of these republications attribute counter-illumination to the killer whale, placing it alongside squid. The term is misused, and the distinction is not a specialist’s detail.

Counter-illumination is active: the animal produces light, by bioluminescence, to erase its silhouette seen from below against the light. This is what certain squid and deep-sea fish do, using light organs.

What the killer whale carries is countershading, in French contre-ombrage: a passive pattern, dark back and pale belly, with no production of light. Penguins, sharks, mackerel and the vast majority of marine animals have it. It is probably the most widespread coloration pattern in the animal kingdom.

Confusing the two amounts to crediting the killer whale with an organ it does not have. Our glossary distinguishes these terms.

What is firmly established

Two uses of these patches are documented, and they concern researchers rather than the animals.

1. They identify individuals. The shape, size and tilt of the patch vary from one animal to another and remain stable throughout life. Combined with the shape of the dorsal fin and the pattern of the saddle, they make it possible to recognise an individual in photographs, year after year. This is what makes possible the individual censuses we have reported on, whether of the killer whales of the world or of the oldest of the Iberian killer whales. Our page on tracking technologies sets out this method.

2. They distinguish ecotypes. The shape of the patch differs systematically between ecologically distinct populations. Type C killer whales in the Antarctic carry a narrow, markedly slanted patch, almost almond-shaped. Type B animals have a broad one. Residents and transients in the north-eastern Pacific are told apart in particular by the pattern of their saddle.

The 2014 work on the North Atlantic provides the clearest example: the killer whales of the Hebrides all carry an eye patch slanted backwards, a feature found in no other population on that seaboard. This group, reduced to a handful of individuals, is now considered doomed for want of any observed reproduction. One of its co-authors, Ruth Esteban, has since signed the demographic study of the Iberian killer whales.

Eye patch	shape, size and tilt specific to the individual and to the ecotype
Saddle	grey pattern behind the dorsal fin, open or closed depending on the population
Dorsal fin	outline of the trailing edge, nicks and scars
Use	individual recognition from photographs, without tagging or capture

A feature that weighed in a taxonomic revision

These differences in pattern are not cosmetic. In 2024, a team led by Phillip Morin published in Royal Society Open Science a revision of the taxonomy of north-eastern Pacific killer whales, concluding that the resident and Bigg’s ecotypes deserve the status of distinct species rather than that of mere local forms.

The case combines genetics, ecology and morphology, and pigmentation is among the morphological features retained.

The proposal was not adopted. The taxonomy committee of the Society for Marine Mammalogy, which decides by a two-thirds majority, gathered a simple majority but not the ten votes required. It created three subspecies instead, Orcinus orca ater, O. o. rectipinnus and O. o. orca, and its reference list, updated in April 2026, still recognises only one killer whale species. We cover this in detail in our article on the 2024 revision.

What can therefore be credited to the white patches is more modest than “redrawing a species”: they are among the features that convinced a majority of taxonomists, without carrying the decision.

The hypotheses on their function, and their actual standing

Three explanations circulate. None has been demonstrated, and that should be said plainly.

Disruptive camouflage. The idea is a classic in the biology of coloration: a high-contrast pattern breaks up the perceived silhouette and prevents an observer’s eye from reconstructing the animal’s real shape. Applied to the killer whale, it would have the patches blur the outline of the head as it approaches prey. The hypothesis is consistent with what is otherwise known about animal camouflage, but it has been the subject of no published test in this species.

The social signal. Killer whales live in stable groups and coordinate complex hunts, as our page on group hunting techniques describes. High-contrast markings could make it easier to hold formation, or to read the orientation of a companion in turbid water. Here again, the idea is plausible and untested.

Simple inheritance. This is the least spectacular explanation and the most often forgotten. A feature can be retained without serving any current function, because it costs nothing and because it comes with a pigmentation pattern inherited from common ancestors. Many delphinids carry comparable contrast patterns without any particular role being ascribed to them.

What the 1993 paper actually describes

Since it is cited, its contents are worth stating. Tiu Similä and Fernando Ugarte observed killer whales in northern Norway, at the surface and underwater, hunting herring cooperatively. They describe there the technique known as the carousel.

The animals encircle a shoal, tighten it into a compact ball while driving it towards the surface, then strike the inside of the ball with their tail flukes to stun the fish, which they then collect one by one. The manoeuvre requires fine coordination between several individuals, and it is specific to certain populations, as our page on group hunting techniques sets out.

The authors note that the animals’ white flank is exposed during the manoeuvre. That is where the idea of a pale belly used to herd fish comes from. But the paper describes a behaviour, it does not test the role of coloration. Thirty-three years on, that distinction still holds.

Why this is so hard to settle

The difficulty is not a lack of interest, it is methodological, and it throws light on the limits of the study of cetaceans in general.

Testing a camouflage hypothesis means measuring the prey’s perception, not ours. One would need to know what a salmon, a herring or a seal sees of an approaching killer whale, at what distance and in what light conditions. That calls for modelling the visual system of each prey species, then simulating the scene. This work has been carried out in other animals, it has not been here.

Testing a social-signal hypothesis would mean observing whether coordination behaviour degrades when the visibility of the patches decreases. No manipulation of that kind is conceivable on an eight-tonne predator, and natural conditions provide no usable equivalent.

That leaves comparison between populations, which is the realistic route: if the shape of the patches varied with prey type or with the turbidity of the water, there would be a clue. That is precisely what no one has yet published.

Where the “solved mystery” appeared

The French text is not an isolated case. It belongs to a chain of republications that can be reconstructed, and that chain is instructive.

Publication	Date	Announces a discovery?
IFLScience, English-language explainer	July 2025	no
Dân Trí (Vietnam), citing IFLScience	16 July 2025	no
vietnam.vn, republication of Dân Trí	16 July 2025	no
Science et Vie	10 August 2025, re-run on 13 August 2026	yes, in the headline

The Vietnamese version, drawn from the same material, presents hypotheses and refrains from concluding. The “researchers have just solved the mystery” appears only at the last link, and only in the headline: the body of the French text claims nothing of the kind. It is an addition of packaging, not a scientific result.

What can be taken from this

The killer whale’s white patch is an excellent tool for researchers and a useful taxonomic feature. Its function for the animal, on the other hand, rests on reasonable but unverified hypotheses.

There is nothing disappointing in that. An open question is a normal state of science, and saying so is better than manufacturing a conclusion. What is a problem is the headline announcing a solved mystery where there is only a recycled popular science article: the reader comes away with a false certainty, and the next study, if it comes, will be received as a repetition.

Our pages on the brain and cognition, social cohesion and diets set out what is otherwise known about this species, and our glossary defines the terms used here.

Sources: Morin P. A. et al., “Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg’s and resident ecotypes deserve species status”, Royal Society Open Science, 2024; Mäkeläinen P., Esteban R., Foote A. and Kuningas S., “A comparison of pigmentation features among North Atlantic killer whale (Orcinus orca) populations”, Journal of the Marine Biological Association of the UK, 2014; Similä T. and Ugarte F., “Surface and underwater observations of cooperatively feeding killer whales in northern Norway”, Canadian Journal of Zoology, 71, 1993. Search for recent publications carried out on Europe PMC on 16 August 2026: no results for the combination of the terms “killer whale” and “disruptive coloration”, and no recent work on the function of the eye patches.