Gray whales (Eschrichtius robustus) were absent from the US Atlantic Coast for about three hundred years — until one showed up off the coast of Florida just north of Miami in December 2023. A short cell phone video was posted online, briefly capturing the whale’s finless, knobbed back and mottled gray skin as it dove into the vibrant blue water. Gray whales are the only baleen whales with such unique characteristics, leaving little doubt of the identification. The video gained wide attention from experts and ocean enthusiasts alike. It was a rare sighting to say the least.

Then, during a routine aerial survey of the waters south of Nantucket on March 1, 2024, researchers from the New England Aquarium, familiar with the marine life of the western North Atlantic, looked down to a surprising sight. Almost certainly the same animal seen in Florida only months prior, what they confirmed was the first gray whale documented in the western Atlantic since before the founding of the United States.

How did a gray whale end up in the Atlantic?

Though relatively common along today’s West Coast of the United States, gray whales are considered to have been extirpated, or driven locally extinct, in the Atlantic by the early 18th century. The loss ended record of the species in the Atlantic that extended more than 44,000 years in the geologic past. But over the last fifteen years, there have been five sightings of the species across the wider Atlantic Ocean; in addition to this animal on the US East Coast, gray whales have also shown up in the Mediterranean Sea and off the coast of Namibia.

It's highly unlikely that we have overlooked gray whales since the 18th century, with more observers and ship traffic than ever before. Instead, the species is likely continuing a long history as long-distance whale immigrants. A 2011 study suggested that a whale seen near Israel and Spain in 2010 traveled up North, around either North America or the Eurasian continent to emigrate from the Pacific into the Atlantic. For the animal seen this year, experts point to the Northwest Passage, a long route from the Bering Sea near Alaska, a popular summer feeding location for gray whales. For the majority of the year, the passage is covered in ice. Scientific records show lower sea ice coverage in the passage in recent years due to climate change, which would make it possible for a whale to make the roughly 100-day swim between ocean basins — and it wouldn’t be the first time they’ve made the journey.

DNA evidence shows that gray whales likely dispersed from the Pacific through the Northwest Passage multiple times during both the Pleistocene, a time period 2.6 million to 11,700 years ago, and during the following epoch, the early Holocene. “Gray whales are actually a very ice-friendly if not an ice-loving species,” said paleontologist Dr. Nick Pyenson. He is the curator of the Smithsonian’s collection of fossil marine mammals and a leading expert on historical populations of gray whales in the Atlantic. To prove his point, he flipped through a guide first published in 1872 by Charles Melville Scammon to show a detailed drawing of these whales swimming up among ice floes. “This is evidence for why it is not a hard thing for gray whales to make it up through the Northwest Passage.”

Ecology of Gray Whales — and what that means for the Atlantic

Nearly driven to extinction by whalers into the twentieth century, the population of gray whales in the eastern Pacific has since rebounded. Today, over 20,000 whales can be found across their extensive migratory range between Baja California and the Bering Sea. According to scientists, the whales seen in the Atlantic are probably wanderers from this population, which has recovered to what scientists consider more or less stable. Opportunistic openings in sea ice and a population possibly nearing its capacity make the perfect recipe for wandering whales.

Historically, grays would have had a similar distribution along the East Coast of the United States, migrating up and down this shoreline from Florida to Maritime Canada. “If you were alive around 300 years ago, you probably would have seen gray whales off the coast of Nantucket, off the coast of Delaware, off the coast of Virginia, off the coast of the Carolinas,” said Pyenson. “But even 300 years ago, the gray whales were probably not especially abundant.”

The historical decline of Atlantic gray whales is still poorly understood. “The big question that really bedevils everybody is whether they were hunted to a degree,” said Pyenson. A specimen in the Smithsonian’s collection, found on the North Carolina coast, revealed evidence of hack marks — a sign that Indigenous people interacted with these animals in some capacity. “Is it an example of whaling culture? That’s hard to say.” With rapid changes in marine environments during the mid-Holocene, studies show a strong likelihood that climate change played a role in their decline, beginning a trend that, in its later stages, was potentially exacerbated by early and commercial whalers.

In the Pacific Ocean, gray whales fill a unique niche in the ecosystem. As predominantly bottom-feeders that often feast on invertebrates living on the seafloor, they are ecosystem engineers, kicking up sediment which then cycles nutrients and distributes food to other organisms in the water column. They can also filter feed like every other baleen whale. As prey themselves, gray whales are also an important food source for mammal-eating killer whales. Gray whales may have played similar roles in historical Atlantic Ocean ecosystems, but — as with many things about extinct whales — it’s hard to say.

What would a gray whale be eating in the Atlantic? Able to feed on a wide variety of prey species and adapt to new environments, gray whales are “ecologically flexible,” according to Dr. Pyenson. “This little lost gray whale is probably making do by eating things that its near relatives don’t feed on, on the Bering seafloor,” he said. One example, a distinct population of the California gray whales known as the “Pacific Coast Feeding Group,” forgoes their typical high-latitude feeding grounds in favor of the area surrounding Vancouver Island in British Columbia, Canada where they use specialized techniques to prey on shrimp during high tides. Seen in good body condition thousands of miles from its expected home range, the wandering whale off the East Coast shows just how adaptable these animals can be.

As global temperatures continue to rise, sea ice continues to retreat, and resources grow scarce, it is possible — and maybe even likely — that more whales will navigate the Northwest Passage and make the trip between ocean basins. But in a future where gray whales do recolonize the Atlantic, they would face the same threats that plague whales in these waters today. As a relatively shallow, shore-hugging species, Atlantic gray whales would navigate some of the busiest waterways in the world and interact with some of the United States’ most valuable coastal fisheries. Entanglements and ship strikes have proven a chronic issue for the critically endangered North Atlantic right whale, a species that can often be found in busy, coastal waters. This year alone, several right whales were killed or injured off of the southeastern United States — the same waters that were possibly once a calving ground for Atlantic gray whales.

Moving forward, protecting whales and other marine life may demand a better understanding of our changing planet and its past — but gray whales show just how adaptable and surprising our oceans can be. Amidst this uncertain future, there may be at least one upside, says Dr. Pyenson, “More whale watches that include gray whales!”