Southern Resident killer whales: 76 individuals, the highest level since 2017

There is one population of killer whales in which every animal carries a number, often a name, and whose genealogy has been known for fifty years. These are the Southern Residents, which frequent the inland waters between Washington State and British Columbia. The census closed on 1 July 2026 counts them at 76 individuals, the highest level since 2017.

A census, not an estimate

The distinction is essential, and rare. For almost every cetacean population, what is produced is a statistical estimate with an interval attached. Here, what is produced is a count.

This is possible because the population is small, coastal, and has been monitored since 1976 by the Center for Whale Research. Every killer whale can be identified by its dorsal fin, its grey saddle patch and its scars. An animal absent through several months of observation, while its family group is encountered regularly, is taken to be dead.

The census is closed each year on 1 July, which makes it possible to compare whole years. Fifty editions make this one of the longest demographic series that exist for a marine mammal, a subject covered by our page on cetacean demographics.

The year in detail

Population on 1 July 2026	76 individuals
Change over the year	+2, about 2.7%
Confirmed births	K47, spotted in December; L130, seen on 14 and 15 June
Newborns lost	L129, born in February and not seen again after June; J64, born in September and missing from October
Deaths of adults or juveniles	none
Length of the count	since 1976, fiftieth edition

The most telling line is not the total but the absence of adult deaths. In a population of this size, the loss of a female of breeding age weighs more than a birth gains, because it takes with it all the calves she would have had.

Four births, two survivors

The newborn tally is the real subject. Four calves appeared during the period, two disappeared before their first birthday.

High mortality in the first year is normal in large cetaceans, and our page on life cycles gives the orders of magnitude. But among the Southern Residents it has been documented as abnormally high for decades, and it is the main brake on recovery.

Three causes are put forward, none of them exclusive. The availability of chinook salmon, on which this population depends closely, and whose stocks are reduced by dams and by fishing. Noise and disturbance from shipping traffic, which reduce the efficiency of hunting by masking echolocation, a mechanism described on our page devoted to ocean noise. And contaminants, PCBs in particular, passed from mother to calf in a very fatty milk, as our page on chemical pollution explains.

These three causes reinforce one another: an underfed female draws on her fat reserves, and so releases the contaminants they store, at the very moment she is lactating.

Why chinook salmon and nothing else

The dietary dependence of this population is so narrow that it deserves an explanation of its own.

The Southern Residents are fish eaters, and about four fifths of their diet is made up of a single species, the chinook salmon, the largest and the fattest of the Pacific salmon. Other fish are abundant in the same waters, coho salmon, rockfish, halibut, but the whales turn to them only marginally.

That fidelity comes down to energy. An adult chinook delivers far more calories than a coho for comparable capture effort, and the energy budget of a killer whale, an animal of several tonnes with a high metabolism, will not bear hunting poor prey for long. Our page on energy and metabolism gives these orders of magnitude.

The contrast with the Bigg’s killer whales, which frequent exactly the same waters but hunt marine mammals, is instructive. The latter are thriving, their numbers are rising, and they benefit from the abundance of seals and sea lions. Two populations of the same species, in the same place, on opposite trajectories: the difference lies entirely in diet.

This is what makes specialisation double-edged. It makes a predator highly efficient as long as the prey is abundant, and condemns it as soon as the prey is lacking, a mechanism we find again in the Iberian killer whales with bluefin tuna. Our pages on diets and on group hunting techniques set out these specialisations.

What a rise of two animals is worth

Growth of 2.7% exceeds the threshold of 2.3% a year that the United States authorities take as a rate of recovery. It would be unwise to draw a conclusion from it.

On a population of 76, two animals fall within demographic noise. A single favourable calving season produces this result, and a single bad year erases it. The population had already seen occasional rises over the past twenty years without the underlying trajectory reversing.

What to take from it, then, is not the figure but its composition: no adult death, two young animals past the first-year mark. If that repeats for three or four years, it will amount to a recovery.

The limits of the exercise

A census of individuals is exceptionally precise, but it measures only what it counts. It gives a population size, not a state of health: two populations of 76 animals, one young and well fed, the other ageing and emaciated, produce the same number.

The indicators that would be needed to settle the question exist in part, drone photogrammetry for body condition, hormone analyses from faecal matter, but they are not summarised in a single figure and do not enter the census.

Finally, some of the disappearances remain uncertain: an animal not seen again is presumed dead, which is almost always correct in a population monitored this closely, but not always.

Set against the Iberian killer whales

Seventy-six individuals on one side, thirty-seven on the other in the Strait of Gibraltar. Two specialised killer whale populations, one on chinook salmon, the other on bluefin tuna, both dependent on a resource exploited by humans, both organised around old females whose loss costs more than one individual.

The difference lies in how long the monitoring has run. We know what happens to the Southern Residents because they have been counted for fifty years. Our page on how many killer whales live in the world shows how far this level of knowledge remains the exception.

Source: Center for Whale Research, annual census of the Southern Resident killer whales closed on 1 July 2026; additional monitoring of the births reported in December 2025 and June 2026.