In our article of 13 August on Toñi, the oldest of the Iberian killer whales, photographed riddled with lead shot, one sentence went past without proof: among killer whales, it is the matriarchs who lead the groups towards resources. This is not a figure of speech. It is a result, obtained over forty years of photographic monitoring, and it carries numbers. Here it is, with what it allows us to say about Toñi’s case and, above all, what it does not.
Since our article: the Spanish state has opened an investigation
We left three unknowns hanging, among them the legal follow-up. One of them has been settled. The Spanish Ministry for the Ecological Transition and the Demographic Challenge states that it was informed on the afternoon of 11 August by the association WeWhale, which operates in the area under administrative authorisation, and that on 12 August it opened preliminary investigative proceedings. The inquiry falls to the Directorate-General for Biodiversity, Forests and Desertification.
The ministry points out that the killer whale population of the Strait of Gibraltar and the Gulf of Cádiz is listed in the Spanish catalogue of threatened species as Vulnerable, and that harm done to these animals constitutes a serious or very serious offence. The penalties incurred can reach two million euros, together with criminal liability.
The two other unknowns remain: no authority has confirmed the origin of the wounds, and Toñi’s condition will depend on what becomes of the projectiles left in her flesh. At the last public sighting, she was still hunting.
Menopause, a trait shared by women and five cetaceans
Among mammals, living for a long time after ceasing to reproduce is an anomaly. The rule is to reproduce to the very end. Menopause is documented only in women and in five species of toothed whale: the killer whale, the short-finned pilot whale, the false killer whale, the narwhal and the beluga.
A study published in Nature in March 2024, led by Samuel Ellis and colleagues on a comparative basis, settled the matter between the competing hypotheses. The result is clear: in these five species, menopause arose because the females extended their lifespan without extending their reproductive span. They live about forty years longer than the females of cetaceans of comparable size, and those forty years are entirely post-reproductive.
The consequence is twofold, and it is what explains the trait. These females increase the time they spend alongside their grandoffspring, without thereby increasing the time during which they are producing calves at the same time as their own daughters. They gain in capacity to help without gaining in competition. A sixty-year-old female killer whale is therefore not an animal that has outlived its usefulness: she is the product of a selection that made this age possible because it serves a purpose.
What they do, and the cost of losing them
What remains to be established is what they contribute in practice. Two pieces of work answer this, on the same reference population: the resident killer whales of the north-east Pacific, followed individually by photographic census since the 1970s.
The first, published in Current Biology in 2015 by Lauren Brent and colleagues, deals with collective movement. Post-reproductive females lead the group to the salmon fishing grounds, and this guiding role is all the more marked when the year is a poor one, that is, when salmon is scarce. A detail that matters for the theory: they guide their sons more often than their daughters. This is the first demonstration that a life prolonged beyond reproduction serves as a reservoir of ecological knowledge.
The second measures what the loss costs. Stuart Nattrass and colleagues published in 2019 in PNAS an analysis covering the two resident populations, monitored since 1976 for the Southern one and 1973 for the Northern one, and covering 378 grandoffspring whose maternal grandmother had been identified.
| Situation in the two years that follow | Mortality risk for the grandoffspring |
|---|---|
| Grandmother alive | reference |
| Grandmother dead, all statuses combined | multiplied by 4.5 |
| Grandmother dead, of post-reproductive age | multiplied by 6.7 |
Two clarifications make this table readable. First, the effect is conditional on food: it appears only below a salmon abundance index of 1.536, and 78 of the 123 recorded grandoffspring deaths occurred below that threshold. An old female counts above all when the resource is lacking, which matches exactly the 2015 result on leadership.
Second, the gap between 4.5 and 6.7 is the heart of the reasoning. A grandmother who is still fertile helps less than a menopausal grandmother, because she is raising calves of her own at the same time. It is the cessation of reproduction, and not age in itself, that frees up the capacity to help.
Three obstacles to transposing this to Gibraltar
It would be easy to apply the factor of 6.7 to the Strait of Gibraltar and draw a conclusion. That would be wrong, for three reasons better stated plainly.
These results do not come from the Iberian killer whales. They come from the north-east Pacific residents, which eat salmon. The Iberian animals hunt bluefin tuna, in a narrow migratory corridor, on an entirely different seasonal cycle. The social structure is comparable, matrilineal in both cases, but the diet and the setting are not. And no one will carry out the equivalent analysis on the thirty-seven Iberian killer whales: with an interval of 8.3 years between two births, the sample would be too thin to test anything at all.
It is not known whether Toñi is menopausal. Female killer whales generally stop reproducing between thirty and forty years of age, and this animal is estimated to be about sixty: it is highly likely. But “highly likely” is not “documented”, and the distinction matters precisely because it is what separates the 4.5 from the 6.7.
This work measures the effect of a death, not of an injury. Toñi is alive and, according to observers, is still hunting. Nothing in the literature makes it possible to convert ten lead shot impacts in a dorsal fin into a probability of death, or to say over what timescale.
What can be asserted is put differently, and remains weighty. In the only population where the question has been measured, the loss of an old female is paid for in the survival of the young of the group, and is paid for all the more dearly when food is lacking. The rest is a reasonable extrapolation, to be presented as such.
A French precedent, and what became of it
France has a file of its own, and it throws light on what usually becomes of this kind of case. On 16 May 2022, a young killer whale was spotted in the Seine, between Rouen and Le Havre. It died there on 30 May, of starvation. The necropsy revealed a round of ammunition lodged at the base of the skull.
The conclusions remained cautious, and still are: the Seine-Maritime prefecture stated that no certainty could be drawn as to the link between this projectile and the death, and that it was not possible to date its entry into the animal’s body. Sea Shepherd France filed a complaint against a person or persons unknown for attempted destruction of a protected species and offered, on 17 July 2022, 10,000 euros for any information making it possible to identify the shooter.
Four years later, to our knowledge, no judicial outcome has been made public. The same sum, 10,000 euros, is on the table today for Toñi. The parallel is not incidental: in both cases the animal is identified, the wound is documented, and the shooter is not. This is the practical limit of legal protection at sea, where the offence is committed without witnesses from a boat that leaves again.
What can be taken from this
Menopause in killer whales is not a curiosity of comparative biology. It is the mechanism by which a population keeps, in the bodies of a few old individuals, the information that allows the others to feed in bad years. A sixty-year-old female in a population of thirty-seven is therefore not one unit among thirty-seven.
Our pages on cetacean life cycles, social cohesion and demographics develop these ideas, and the culture of sperm whale clans shows that the transmission of group knowledge is not peculiar to the killer whale. To take action, see how to act for cetaceans.
Sources
- Spanish Ministry for the Ecological Transition and the Demographic Challenge, press release: opening of preliminary investigative proceedings, 12 August 2026.
- Ellis S. et coll., 2024. “The evolution of menopause in toothed whales”. Nature 627: 579-585. doi.org/10.1038/s41586-024-07159-9.
- Brent L. J. N., Franks D. W., Foster E. A. et coll., 2015. “Ecological knowledge, leadership, and the evolution of menopause in killer whales”. Current Biology 25: 746-750. doi.org/10.1016/j.cub.2015.01.037.
- Nattrass S., Croft D. P., Ellis S. et coll., 2019. “Postreproductive killer whale grandmothers improve the survival of their grandoffspring”. PNAS 116: 26669-26673. doi.org/10.1073/pnas.1903844116.
- Esteban R., Gauffier P., López A. et coll., 2025. “Demographic Parameters of Iberian Killer Whales Between 2011 and 2023”. Marine Mammal Science. doi.org/10.1111/mms.70088.
- Killer whale in the Seine, necropsy and aftermath: CNEWS, 6 July 2022 and CNEWS, 17 July 2022.
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