Three mystery whales have been surprising whale watchers from Canada to Olympia.

When somebody gets the thrill of seeing an orca in Northwest waters, that whale is almost always well known. Scientists have probably given it a number and documented its family tree, perhaps even its DNA. Whale lovers have probably given it a cutesy name, like Yoda or Kelp.

But on March 6, a trio of orcas showed up in Canada’s busy Vancouver Harbour, later heading south to Seattle, Tacoma, and Olympia, that were a mystery to scientists.

For decades, researchers have compiled photographic catalogs of essentially all the orcas of the Pacific Northwest, including the endangered southern resident killer whales and the more abundant, mammal-eating Bigg’s killer whales, also known as transients.

Photos taken during the four days that the trio of whales spent in a busy harbor bounded by Vancouver’s Lions Gate and Trans-Canada Highway bridges showed these were Bigg’s killer whales, but they matched none of the whales in the catalogs.

“We couldn’t place these individuals,” said Jared Towers, head of Bay Cetology, a whale-research organization based in Alert Bay, British Columbia. “At first, the photos weren’t great quality, but from what we could see, these whales were new. It took a few days, but when we finally got good photos, we were able to confirm that they were indeed new whales for the region.”

Towers said it was very rare for a new orca to be spotted anywhere in British Columbia.

“In the Salish Sea, it’s absolutely unheard of,” he added.

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Higher-quality photos revealed the trio had highly unusual, circular markings, about the size of a large chocolate-chip cookie.

“One of the things that was really notable were these circular scars, which are remnants from cookie-cutter shark bites,” said Gary Sutton, a whale researcher with the Vancouver-based nonprofit Ocean Wise.

Cookie-cutter sharks live far from land in the deep, open ocean, usually in much warmer waters, typically south of Hawaii. The small sharks, sometimes called cigar sharks, spend their days 3,000 feet or more underwater and have undersides that glow green in the ocean depths. They rise closer to the surface at night.

How this tiny shark feeds might be its most unusual characteristic: It latches onto much larger prey with sucking lips and sharp teeth, then spins its body to remove a cookie-shaped plug of flesh from its victim.

“They’re micro-predators, like a horsefly or something,” Towers said.

All three of the orcas, a female and two younger males, had scars indicating they had spent time in cookie-cutter shark country.

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Word and photos of Vancouver’s mystery orcas reached marine biologist Emma Luck in Alaska. A year earlier, she had been alerted to a trio of mystery orcas in Turnagain Arm near Anchorage. Orcas are fairly common in Alaska but rare near Anchorage.

“Apparently, the whole of Anchorage had received the same news, because cars were packed into every available inch of highway pullouts and shoulders,” Luck said on Facebook. “People climbed on top of their vehicles, trying to catch sight of the three black dorsal fins cutting through the water.”

The Anchorage trio had never been documented before or since.

When Luck saw photos of the Vancouver trio, something clicked.

“To my astonishment, I recognized them immediately: they were our Anchorage whales,” Luck said.

“They have been spending time in the tropics, occasionally, and obviously, they’ve been seen up in Alaska, so they’re moving around a lot,” Towers said.

The well-traveled trio apparently left Canada on Monday and swam to Seattle, even entering the heavily industrial Duwamish Waterway before continuing south to Tacoma and Olympia.

“It was almost a year ago that these animals were seen up in the biggest city in Alaska, and the next time they were seen was the biggest city in British Columbia, of course, followed up by the biggest city in Washington State,” Sutton said. “So, these guys are on a little city slicker tour.”

An underwater microphone at the Highline College aquarium in Des Moines captured their calls as they swam into south Puget Sound on Wednesday.

It remains unclear which population of killer whales the mystery trio belong to. Bay Cetology has given them numbers: T419, T420, and T421, while California-based researchers with the Oceanic Research Alliance have given them competing monikers: OCX085, OCX086, and OCX087.

“My best guess is that they are either poorly documented Gulf of Alaska Bigg’s killer whales or perhaps far-flung visitors from the Aleutian Islands or Bering Sea,” Luck said.

The trio was spotted hunting seals at the Port of Olympia on Thursday.

Why these ocean-roaming predators have been hunting in such urban waters instead of their usual haunts is anyone’s guess.