A mystery pod of orcas surprised Seattle whale watchers

The killer whales of the Salish Sea, off the coast of British Columbia and Washington State, are perhaps the most well-studied marine mammals in the world. For over 50 years, researchers have taken thousands of pictures of these populations to catalog them by their dorsal fins, each of which is unique as a fingerprint.

So it came as a surprise when, in mid-March, three previously unknown killer whales, also known as orcas, entered Vancouver Harbor.

"I can't recall a time when we've had unknown adult whales turn up in the Salish Sea, at least in the last 25 years since I've been here," said Monika Wieland Shields, director of the Orca Behavior Institute.

First spotted near Anchorage in March 2025, the three "mystery orcas" were next seen off the coast of Vancouver earlier this month before moving south toward Seattle. Most recently, as of the afternoon of March 24, they appear to have returned to Puget Sound, according to the Orca Conservancy.

The adult female, juvenile male, and calf are likely from a population known as Transients from Alaska, and now have scientific catalog names T419, T420, and T421. 

As scientists scramble to learn more about them, questions abound over what drove these mystery orcas into the Salish Sea, and what this could mean for the already-vulnerable local populations.

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Strangers in a strange land

There are a few clues as to the trio's identity. The orca ecotypes—genetically distinct populations that frequent the same waters but do not interbreed—of the northeast Pacific Ocean are distinguished by their diets, their unique calls, and other characteristics. Transient killer whales, also known as Bigg's killer whales, are mammal eaters and travel in small groups. Southern Residents and Northern Residents prefer salmon.

They also have slight differences in appearance. Wieland Shields identified the three strangers by their slanted eye patches and larger saddle patches — the white area found behind the dorsal fin—clear signs that they belong to the Transient ecotype.

"Now that we've seen them pursuing [harbor] seals, we're certain," she says.

Marks on their bodies help narrow down their usual habitat. Scars on the killer whales' backs indicate damage from cookiecutter sharks—parasitic sharks that bite out chunks of tissue in a "cookiecutter" fashion, leaving circular marks.

Transient killer whales from Alaska can have these scars, though the nearest habitat for cookiecutter sharks is southern California, according to University of Alaska Fairbanks marine scientist Emma Luck. Since this trio was first spotted in Alaska last year, scientists’ working theory is that the orcas are Alaskan Transients who regularly migrate south. 

This isn't especially surprising behavior for Transients. Killer whales' specialized diets help us predict the different populations' movements, says Rus Hoelzel of Durham University, as they follow the migration patterns of their prey.

"Those that pursue marine mammals tend to have very broad geographic ranges, which may be seasonally predictable," he says. "But we often don't know their full range, and it can change especially if their resource distribution changes." 

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A family affair

Researchers have followed the trajectory of the killer whales closely since their arrival.

First spotted on March 5, the orcas spent four days in Vancouver Harbour before leaving the area during the night of March 8 or the morning of March 9, according to Bay Cetology, the organization that catalogues these populations of killer whales.

They then moved further south toward Seattle, where they spent a couple of days before moving back north to Admiralty inlet, near the exit into the Pacific Ocean.

The whales were then seen on the 14th, but they may have been heard in the early hours of the 15th: Wieland Shields speculates that they were responsible for the "bizarre vocals" recorded on a Port Townsend hydrophone; those don't match any known populations, she says. They appear to be back in Puget Sound as of March 24, according to the Orca Conservancy.

Over the course of their visit, the killer whale "tourists" stuck together. Since orcas usually travel with matrilines, Wieland Shields says, she assumes the adult female— females have short, curved dorsal fins—is the mother of the two other killer whales, which appear to be much younger.

Her companion has a tall, straight dorsal fin, typical of a juvenile male. The third orca is smaller in size, with a short, curved dorsal fin typical of calves. Wieland Shields estimates it is around five years old.

T419 has a jagged cut on the inside edge of her dorsal fin, making her especially distinctive.

"It's not at all uncommon for orcas to have scars, notches, etc.," said Wieland Shields. "These can be caused by other killer whales, or in the case of mammal-eating killer whales, could also be an injury from prey."

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Friends or foes

Will the mystery orcas play nice with the locals? There are less than 80 Southern Resident killer whales left in the Salish Sea, so any threat to this endangered population could have disastrous consequences.

Wieland Shields isn't worried, as the ecotypes in the Salish Sea rarely interact, and it's "extremely unlikely" that the visitors would pose a threat to Resident orcas. In fact, Residents and Transients in this area have lived alongside each other in this area for centuries, says Michael Weiss, the research director at the Center for Whale Research and a Southern Resident killer whale specialist.

But during their time in Puget Sound, the mystery orcas have been spotted interacting with the locals there.

"It's interesting to see them affiliate rather than be chased out or avoided," Wieland Shields says. "That raises the potential that there could be some amicable interactions like potential mating, which could result in a new genetic influx to our local population."

While inbreeding isn't as big of a concern for Transients as it is for the Southern Residents, genetic diversity is low, she says, and interbreeding could benefit the population.

Their motivation for traveling to the area remains a mystery. Transients are more likely than Residents to venture far from their normal ranges, and Wieland Shields says killer whales' incredible sense of direction tells her they're probably not lost.

The mother may have simply decided to take her kids on a vacation. "Perhaps she's just an explorer by nature," Wieland Shields says.