Here’s what we know — and don’t know — about the fin whale that washed up on the Anchorage mudflats

Of all the kinds of whales that could have washed onto the Anchorage mudflats, a fin whale is one of the most mysterious.

Whale strandings are fairly routine in Alaska. But the latest, in which a juvenile fin whale appeared last weekend on the tidelands beside the city’s most popular recreational trail, is exceptional for several reasons.

Chief among them is the species itself: Though fin whales’ range includes the waters up and down Alaska‘s coast all the way to the Arctic, they‘re rarely seen. Especially in upper Cook Inlet.

Researchers don’t yet know how the young female died. For three days, a small team of trained volunteers cut out samples of the whale’s flesh and organs to send off for analysis, which may eventually lead to a conclusion about what killed it.

In the meantime, the carcass has become a local attraction, drawing hundreds of people a day to the frosty mudflats, which people are typically discouraged from venturing onto. Social media has been filled with posts about the rare, unique, moving experience of a school bus-sized creature washed up so close to town that it can be touched and photographed.

“Luckily it’s in the single digits so the carcass is frozen solid, so there was only a light smell. It was truly remarkable to see an animal this large up close! And what an amazing learning experience for my boys,” wrote one woman on Facebook.

“It was fascinating to see the baleen in its mouth and feel the soft skin. Although it was mostly frozen, it did NOT smell pleasant,” wrote another.

The animal may be around for a while.

“We’re going to leave it to nature,” said Barbara Mahoney, a biologist with the National Oceanic and Atmospheric Administration.

The high tides that carried it so close to the city, and may carry it back out to sea, are not forecast to reoccur for weeks. And even then, the carcass may be frozen in place.

Unusual in Upper Cook Inlet

They’re called fin whales because of a small, distinct dorsal fin on their otherwise smooth backs down toward the tail.

Among the world’s many whale species, fins are some of the least understood. That’s in part because of where they spend their time: generally in deep, open ocean far from shore.

“Most migrate from the Arctic and Antarctic feeding areas in the summer to tropical breeding and calving areas in the winter. The location of winter breeding grounds is not known. Fin whales travel in the open seas, away from the coast, so they are difficult to track,” says a species overview from NOAA.

There are fin whale stocks all over the globe, from temperate polar oceans to the Mediterranean Sea.

“The overall migration pattern is complex and likely varies by region,” according to NOAA. There are some groups that appear to be resident populations, seeming to permanently stay within bodies of water like the Gulf of California and East China Sea.

After blue whales, fins are the second longest of the large cetaceans. They grow to between 75 and 85 feet long, which is part of how local officials determined the stranded female, at 47 feet from mouth to flukes, is a juvenile. Mahoney said the whale “looks young,” but conceded she is not an expert on big whale species.

Fin whales are sometimes observed farther down Cook Inlet, closer to its mouth, not in the upper reaches beyond Turnagain Arm.

When dead fin whales are found in Alaska, it tends to be during summer, not the middle of November. In 2015, 12 fin whales became stranded and died between May 22 and June 17 near Kodiak Island and the western Gulf of Alaska, along with 22 humpbacks that same year. The incident was classified as an “Unusual Mortality Event,” likely caused by ecological factors, according to a 2017 report from NOAA.

In a separate paper, researchers looked at all the human-caused “mortality and injury” to large whales over a five-year period in Alaska, and found 117 official instances. Fin whales accounted for just three of those. In July 2014, a fin whale was struck by a cargo ship in Western Alaska. In May 2016, a cruise ship arrived in Seward with one smashed against its bow. And in June 2018, there was an unfortunate incident in which a whale collided with a state ferry off of Kodiak.

No signs of injury

So far, there are no signs that the fin whale on the mudflats was hit by a ship or similarly injured.

“Nothing’s external. Like, there’s no rope marks, there’s no fish lines, there’s no prop marks,” Mahoney said. “There’s no crushed anything.”

As she spoke, volunteers with Alaska Veterinary Pathology Services wearing heavy-duty rubber smocks dug through the carcass with blades and hand tools, gathering tissue samples that might eventually yield clues about whether disease or injury might have killed the young whale.

“They got feces, they got pieces of the heart, they got pieces I think of the intestines, they got parts of the stomach. So it’ll be looked at,” Mahoney said.

She doesn’t know fin whales well enough to say whether this one looked skinny, but pointed to rectangular scraps of skin and fat that had been carved out and were sitting on the ice a few feet away.

“It had a good layer of blubber,” Mahoney said.

There’s no clear explanation yet for how the animal died, she said.

Fin whales eat small schooling fish like herring, as well as krill, and squids. They roll onto their sides and lunge at swarms of tiny sea creatures, gulping them down, then filtering the water out through their baleen. They can eat two tons of food in a day. In winter, they fast.

Fin stocks worldwide were decimated by commercial whaling. Now, the only approved hunting is by subsistence users in Greenland, who harvest an average of 14 a year. There’s no quota allotment for fin whales in Alaska.

Though they’re listed as an endangered species, global population estimates for fin whales are spotty, in part because their preferences for deep oceans makes them hard to reliably survey. A 2020 research paper estimating the stock in the northern Pacific Ocean, which includes the waters off Alaska, put the minimum number of fins in the region at 2,554, though conceded this was surely an undercount because there’s so little data for most of their habitat area.

Ice mud

By Tuesday afternoon, as the volunteers were wrapping up their sampling work, they had unanchored the carcass so that a potential high tide could carry it away from the mudflats and town.

But it’s not clear how long that will take.

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Two pedestrians look at a 47-foot fin whale carcass, which washed ashore in November, near Fish Creek in Anchorage on December 12, 2024. (Marc Lester / ADN)

An exceptionally high tide last Saturday night, 33 feet, managed to carry the carcass far from the inlet’s deeper channel and deposit it on the tidal flats, a few hundred yards from a scenic overlook at a bend in the Tony Knowles Coastal Trail near Fish Creek. According to projections from NOAA, high tides aren’t expected to get up to 30 feet in Cook Inlet again until Dec. 11, right before next month’s full moon. Even if the water comes as high as it did this past weekend, the carcass appears to be freezing in place and may be much harder to budge, Mahoney said.

The whale’s accessibility may pose risks, too. Despite subfreezing temperatures, crowds of people have been traipsing past Westchester Lagoon and down the Coastal Trail before descending onto the frozen mudflats, where cautionary signs warn people year-round not to go lest they get stuck, as often happens in summertime. Last year, a 20-year-old Illinois man drowned on the mudflats near Hope after getting stuck.

Tuesday’s visitors to the whale represented the same kind of broad cross-section of Anchorage residents you’d see at Costco on a Saturday. Plenty were geared up, bundled against the cold, with cleats and hiking poles to cross slick ice. Others wore ripped jeans, thin sneakers, hoodies and, in one instance, pink Crocs sandals. One woman in black heels cautiously toddled toward the whale over frozen mud hummocks to snap a selfie. Children who’d grown bored with the carcass ranged freely around big ice chunks, or cried from the cold.

“Asher, sit next to Felicity,” a mother yelled at her kids, arranging them for a photo in the alpenglow reflected off a frozen puddle.

“We all know how dangerous the mudflats are,” said Mike Braniff, head of Anchorage’s Parks and Recreation Department, which is in charge of the Coastal Trail but not the tidal lands below it.

In the 2017 humpback stranding near Kincaid Park, the department helped coordinate access for federal agencies responding, Braniff said. This time, because of how readily accessible the fin carcass is, they are not even engaged in that capacity, he said.

Mudflat dangers

The department is considering using its social media channels to inform members of the public about the dangers of trekking out to the mudflats.

“Right now we’re in a posture taking a pretty hands-off approach,” Braniff said.

He added that in the case of a large attraction like the dead whale, there’s a potential risk in adding signs along the trail.

“Does putting up signage at the location actually drive more traffic unintentionally?” Braniff posed. “Does it become way-finding instead of cautionary?”

Another consequence of the new attraction is a huge boost in vehicle traffic in the residential area next to the closest trailhead, a warren of narrow dead-end streets and cul-de-sacs that have been jammed with parked cars and pedestrians the last several days.

“While it’s exciting to get up close and personal with this beautiful creature, please be safe and seen. If you are walking on any of the neighborhood streets to get to the Coastal Trail, please wear headlamps and reflective safety gear so cars can see you,” wrote Diana Rhoades, program director for the Anchorage Park Foundation, in an email.

“On the trail, please dress warmly for winter and put on your spiked shoes. Lastly, don’t go out on the mudflats without knowing the tides,” Rhoades added. “The high tides are likely what brought the whale to us, and we don’t want them to take you away.”