Scientists aren't sure how whales navigate during long underwater migrations, but a new study lends credence to the idea that they use Earth's magnetic field to orient themselves.

The research found that during solar storms, gray whales are more likely to get stranded on shore.

The researchers suggests that these solar storms cause gray whales' internal compasses to shut down, preventing them from navigating accurately.

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More than 200 gray whales got stranded or washed up dead onshore in the northeastern Pacific Ocean last year.

Often, these strandings are the fault of humans: Whales collide with boats, get entangled and choke in fishing nets, or swim away from underwater sonar sounds. But a new study shows that some whales might get beached because of a different threat: the sun.

On days with more sunspots — the sources of solar flares and storms that hurl high-energy particles towards Earth — researchers found that gray whales are more likely to strand themselves on shore.

Jesse Granger, the lead author of the new study, told Business Insider that the energy from solar storms might mess with the whales' ability to navigate underwater.

"We think whales are getting stranding more often during solar storms because they've gone blind," Granger said. "The impacts of these storms on Earth could be shutting down the animals' ability to sense the magnetic field."

More solar storms, more stranded whales

Past research has suggested that migratory whales use the planet's magnetic field to orient themselves, since, as the authors of the new study said, "visual cues in the ocean are often limited."

Their new research lends further credence to that idea, Granger said, but doesn't prove it.

A gray whale calf expels air through its blowhole as a boat filled with visitors watches in the San Ignacio lagoon off Mexico's Baja peninsula, March 3, 2015. Dario Lopez-Mills/AP

Granger and her colleagues' study used data from the National Oceanic and Atmospheric Administration (NOAA) about 186 gray whales that got stranded in the US between 1985 and 2018. That's not the total number of whales stranded during those years — the team only looked at those stranded alive (or that had very recently died) with no signs of injury, illness, emaciation, or interaction with boats, people, or nets.

"These were very likely totally healthy, uninjured whales that, for some reason, ended up on land," Granger said.

The reason, she thinks, is a navigational error.

The data showed that gray whales were more than twice as likely to get stranded on days with a high number of sunspots: more than 151. That suggests something about solar storms stymies whales' ability to determine how close they were to shore.

Earth is surrounded by a giant magnetic bubble called the magnetosphere, which deflects charged particles from the sun. NASA

Granger's team thinks the culprit is the radio-wave noise that energy from solar storms produces when it reaches Earth. The data showed that, on days that included high amounts of this radio-frequency noise, gray whales were more than four times more likely to veer off-course and get stranded.

The researchers think this noise resonates at a frequency that can shut down or mess up some animals' abilities to sense the magnetic field. Studies have shown that this happens in birds, cockroaches, snapping turtles, hamsters, and dogs, Granger said. So it could easily apply to whales, too.

Tourists are greeted by a friendly gray whale while whale watching in the San Ignacio Lagoon, Mexico. Mark Carwardine / Barcroft Media / Getty

"I was definitely not expecting to find evidence that a whale's GPS could be completely shutting down during a solar storm, rather than the animal simply making a navigational error," Granger said.

Whale strandings typically involve factors other than solar storms

Pinpointing the reasons why gray whales get beached is a crucial for conservation efforts.

"Many things can cause a stranding," Granger said, adding: "This solar effect is not a major one."

The Asian gray whale population consists of just 200 whales (or fewer) and is listed as endangered. About 27,000 whales migrate up and down the western shores of North America, meanwhile, and are not currently listed as endangered. But in 2019, hundreds of North American gray whales washed ashore dead, and experts suggest they were just 10% of the total number of dead whales last year, since other carcasses sank to the ocean floor or were eaten by predators.

The primary threats to whales are ocean noise, fishing nets that can entangle them, collisions with boats, and warming waters (which harms their preferred food supply).

A dead gray whale in the Pacific Ocean. Courtesy of Jesse Granger/edited by Danielle Granger in collaboration with Virginia Tech's Architecture and Design

Still, identifying a link between solar activity and whale behavior may further illuminate the reasons these creatures sometimes end up so far from their preferred deep-ocean habitat.

Going forward, Granger said, she hopes to gather data from other species of migrating whales off the coasts of Australia, New Zealand, and the UK to see if she finds the same pattern.