How many killer whales are left in the world?

How many killer whales are left in the world? The question looks simple. The answer is much less so. Orcinus orca is the only officially recognised killer whale species, but beneath that taxonomic unit lies a remarkable behavioural, genetic and cultural diversity. Several “ecotypes” are so distinct that they are being reclassified as separate species or subspecies. The world total is estimated at about fifty thousand individuals, but that figure conceals enormous disparities: some ecotypes are numerous and stable, others are on the brink of extinction.

Short answer: about 50,000 killer whales worldwide, of which 25,000 to 30,000 in Antarctic waters. Several small populations are critically endangered: 74 Southern Residents (Salish Sea), 40 to 50 in the Strait of Gibraltar, and the European populations as a whole, threatened by PCB contamination.

One species, ten ecotypes

Science officially recognises a single killer whale species, Orcinus orca. But that species harbours subgroups known as ecotypes, which differ radically in their feeding, their vocalisations, their morphology and their social organisation. At least ten ecotypes have been identified, and some are in the process of being raised taxonomically to distinct species.

In the North-East Pacific, three main ecotypes are distinguished: the residents (chinook salmon eaters, vocal, living in stable matrilineal pods), the transients or Bigg’s (marine mammal eaters, silent while hunting, living in small groups), and the offshore killer whales (shark eaters, mainly Pacific sleeper sharks, living in larger groups but little studied on account of their remote habitat).

In the Antarctic, five ecotypes have been identified and named A, large B, small B (“pack ice”), C and D. Type A is the largest, and hunts minke whales. Type B “pack ice” specialises in wave washing against Weddell seals. Type C, the smallest, hunts mainly toothfish. Type D has a particularly bulbous melon and lives at the margins of the circumpolar current. All of them meet geographically but do not interbreed, a major criterion for speaking of distinct species.

Other ecotypes exist in the North Atlantic, the tropical Pacific, the Indian Ocean and around Australia. The acoustic and behavioural diversity is such that researchers including Phillip Morin (NOAA) proposed in 2024, in Royal Society Open Science, formally separating the North-East Pacific residents (becoming Orcinus ater) from the Bigg’s killer whales (becoming O. rectipinnus). The formal taxonomic decision is under review by the Society for Marine Mammalogy.

The critically endangered populations

Several populations are now in a worrying state. The Southern Resident killer whales (Salish Sea, on the United States/Canada border) numbered 88 individuals in 2003, and only 74 in 2024. The decline is slow but persistent. The causes: the collapse of their sole prey, the chinook salmon (itself threatened by dams, overfishing and warming); heavy shipping traffic in the Salish Sea; chronic PCB contamination. In 2018, the killer whale J35 (Tahlequah) drew attention around the world by carrying the body of her dead calf for 17 days and 1,600 kilometres. A symbol of how precarious the population is.

The Strait of Gibraltar killer whales are another emblematic population. It numbers between 40 and 50 individuals, specialising in hunting Mediterranean bluefin tuna, themselves threatened by overfishing. Since 2020, these killer whales have developed a disconcerting behaviour: they interact frequently with sailing boats, biting at and damaging their rudders. Several hundred interactions have been documented between 2020 and 2024. The origin of this behaviour remains debated, a response to the past trauma of one central individual in the population, or simply an innovative cultural game, but it has placed this population under the international spotlight.

The European coastal killer whales as a whole show the highest PCB contamination levels in the world. See our page on contaminants. Jean-Pierre Desforges and his team published particularly bleak projections in Science in 2018: according to their models, several subpopulations (Iberian, coastal Norway, British Isles) are doomed to extinction within the next 30 to 50 years through reproductive collapse linked to chemical toxicity. The reproductive toxicity thresholds have long been exceeded.

The stable and numerous populations

At the other end of the spectrum, some populations are doing relatively well. The Norwegian killer whales that hunt herring in open water (with a spectacular technique known as carousel feeding, in which they encircle the herring and gather them into a tight ball) number several thousand individuals. The Icelandic killer whales are also in good shape. The Antarctic killer whales, all types taken together, are estimated at between 25,000 and 30,000 individuals, the largest concentration in the world.

The world total estimate of about 50,000 killer whales (IUCN) is therefore dominated by these Antarctic populations. That figure is probably an underestimate, however: vast areas of the tropical Pacific and of the Indian Ocean have been little surveyed, and new populations are identified regularly.

A paradoxical situation

The killer whale illustrates a paradox of modern conservation: a species that is stable overall can harbour local populations that are seriously threatened. The global IUCN status of Orcinus orca is “Data Deficient” (DD), because the diversity of ecotypes and populations makes a single assessment difficult. But several subpopulations are individually listed as Endangered or Critically Endangered. If the taxonomic promotion by Morin et al. is accepted, some ecotypes will appear as separate species and their status will be reassessed, revealing situations hidden beneath the “Orcinus orca” aggregate.

Sources

IUCN Red List, Orcinus orca, Data Deficient (globally). Subpopulations listed as Endangered or Critically Endangered.
Desforges, J.-P. et al. (2018). “Predicting global killer whale population collapse from PCB pollution”. Science, 361.
Center for Whale Research, census of the Southern Resident killer whales, 2024 update.
Morin, P.A. et al. (2024). “Revised taxonomy of eastern North Pacific killer whales”. Royal Society Open Science.
De Stephanis, R. et al. (2008). “Spatial and temporal distribution of killer whales (Orcinus orca) in the Strait of Gibraltar”. Marine Mammal Science, 24.