For years, whale watching enthusiasts have flocked to West Coast shores to catch a glimpse of migrating gray whales. These gentle giants inhabit waters in the Pacific Ocean, while their numbers in the Atlantic Ocean gradually dwindled to the point of extirpation, or local extinction, centuries ago. It came as a colossal shock, then, when a single gray whale was spotted on the other side of the country near New England earlier this month. 

On March 1, aquarium scientists first noticed the whale diving and resurfacing during an aerial survey 30 miles south of Nantucket, as explained in a news release. This turned out to be the fifth documented observation of a gray whale outside the Pacific in the last 15 years. One was previously seen off the coast of Florida in December 2023, although scientists now think this is the same whale just seen near New England. 

“My brain was trying to process what I was seeing, because this animal was something that should not really exist in these waters,” said Kate Laemmle, a research technician who was in the plane, in a press release. “We were laughing because of how wild and exciting this was — to see an animal that disappeared from the Atlantic hundreds of years ago!” 

Why Did Gray Whales Disappear From the Atlantic Ocean?

Gray whales — known for their lack of a dorsal fin and mottled skin — once swam in Atlantic waters, but they met an unfortunate end likely spurred by commercial whaling, which involved hunting and killing whales to sell their meat and blubber.

Colonial Americans began commercial whaling in the 1650s, becoming a leading force in the industry over the next two centuries. By the 18th century, gray whales were driven to extinction in the Atlantic. 

Gray whales currently live in the North Pacific Ocean, where two populations exist: one in the western Pacific, off the coast of Asia, and one in the eastern Pacific, going down from the Alaskan coast all the way to Mexico.

Eastern North Pacific gray whales feed up north during the summer, and then migrate south in the fall. Calves are usually born around January or February off the coast of Mexico. The following months are spent migrating back north, attracting droves of avid whale watchers in the U.S. 

However, rare sightings of gray whales in the Atlantic have stirred excitement from time to time, leading to speculation about the species’ sporadic appearances near the East Coast.

“This sighting highlights how important each survey is. While we expect to see humpback, right, and fin whales, the ocean is a dynamic ecosystem, and you never know what you’ll find,” said Orla O’Brien, associate research scientist in the Anderson Cabot Center for Ocean Life at the New England Aquarium, in the release.

Read More: Why Are Gray Whales Moving to the Ocean Next Door?

A Consequence of Climate Change

Scientists suggest that climate change could explain these surprise sightings. The Northwest Passage, a well-known sea route that connects the Atlantic and Pacific through the Arctic Ocean in Canada, has been losing more sea ice in recent years due to rising global temperatures. Sea ice normally limits the range of gray whales since they can’t break through it, but declining levels of ice means the passage is often clear enough to traverse during recent summers. 

This may be what ties together the various isolated sightings in the Atlantic and even as far as the Mediterranean Sea (one gray whale was seen near Israel in 2010, and another in 2021 close to southern France). In these cases, including the recent sighting, the whales probably end up in the Atlantic simply by accident, swimming the wrong way during their stay up north.

Sightings could happen more frequently as sea ice melts and the Northwest Passage becomes increasingly navigable, allowing the whales to wander from their natural habitat.

“These sightings of gray whales in the Atlantic serve as a reminder of how quickly marine species respond to climate change, given the chance,” said O’Brien in the release.

Read More: How Many Whales Are Left In the World?