Sperm whales are the largest of the world’s toothed whales—smaller than giant, filter-feeding blue whales, but still the size of four big elephants—and they live out in the deep ocean, where they feed on squid, along with the occasional octopus, ray, or shark. In Iceland, or western Norway, or around the Azores, places where the continental shelf drops off close to the coast, these whales sometimes swim into view of human civilization. Still, they’re rarely spotted at all and almost never in the sandy, tidal North Sea, a cul-de-sac of the Atlantic Ocean between the United Kingdom and Norway.

On a January afternoon in 2016, though, Dirk-Henner Lankenau, a biologist at the University of Heidelberg, was beachcombing on the German island of Wangerooge when two dark forms appeared in the distance. When he reached the shapes, Lankenau found that they were whales, stranded overnight on the shore and already dead. Four days later, another two sperm whales were seen floating, dead, off the coast of a nearby island. That same day five more were found marooned on the Dutch island of Texel. Another two washed up soon after. The next week another dead whale showed up on a British beach, with more to follow. Within weeks, 30 sperm whales had perished on cold North Sea shores.

The whales were all males, on the younger side, and likely belonged to the same pod of bachelor sperm whales, up from southern waters to feast on squid in the Norwegian Sea. Sperm whales are normally good navigators that travel from polar to equatorial seas, but somehow this group had taken a deadly detour into the shallow, relatively squid-free North Sea.

A beached sperm whale, as depicted in the <em>Visboeck</em>, a Dutch work from 1577.
A beached sperm whale, as depicted in the Visboeck, a Dutch work from 1577. Public Domain

These unfortunate whales were not the first of their kind to become trapped in the North Sea, unable to find their way back to the open ocean. For centuries now, people have documented stranded whales on these coasts. Many years are free of incidents, or see only a lone example of a lost whale. But there have also been dramatic mass beachings in 1577, 1723, 1762 (when more than two dozen dead whales were found), and 1994.

For all those centuries, the cause of these mass deaths has been a mystery. Whales that die in this way tend to be in good health, with no signs of illness or malnutrition, and their deaths have come in no clear pattern that might hint at what happened. The long history of the strandings mean that it’s hard to blame humans, exclusively at least, for causing them.

Perhaps, though, we should blame the Sun.

In a new paper, published this August in the International Journal of Astrobiology, physicist Klaus Heinrich Vanselow and his colleagues develop a theory, first advanced more than a decade ago, that whale strandings in the North Sea are caused by solar storms. Million miles away, the Sun spits out clouds of energy and particles so large they can distort Earth’s magnetic field. When they hit the planet, these magnetic fluctuations may make whales lose their way with serious, even fatal, consequences.

A 17th-century depiction of a beached sperm whale at Noordwijk in the Netherlands.
A 17th-century depiction of a beached sperm whale at Noordwijk in the Netherlands. Public Domain

When an animal this large shows up dead on shore, it is an event. As far back as the 16th century, when sperm whales beached near important cities in the Netherlands, artists documented the demise with etchings and engravings. In the 18th century, one stranding was commemorated with a set of blue Delft plates. These images, often printed in pamphlets and distributed across Europe, show crowds gathered around the massive corpses but also depict the whales in fine detail. For many years, much of what Europeans knew about sperm whales was learned from these events.

The whales found stranded in the North Sea have always been males because of the differences in how male and female whales live. Sperm whales breed in equatorial oceans, and young whales remain in those waters with their mothers for at least a few years, and sometimes well into adulthood. After leaving their mothers, male whales form groups of their own, which travel far from the breeding waters. Sperm whales share our taste for squid, and the bachelor groups follow them north. The groups the bachelor whales form are not always tight-knit, but still they can lead each other into trouble.

Map of the North Sea, 1906.
Map of the North Sea, 1906. Public Domain

The whales that get lost in the North Sea are on their way back south. Usually, they would skirt around Scotland and Ireland to get back to the Atlantic, but sometimes they turn south too sharply and too early—into the North Sea, which has sandbanks, estuaries, and tides more dramatic than they’re used to.

“The North Sea … is totally unsuitable for sperm whales,” wrote Chris Smeenk, of the Netherlands’ National Museum of Natural History, in a 1997 paper on the history of whale strandings. “Being animals of the deep ocean, sperm whales have no experience whatsoever in finding their way in this kind of shallow and treacherous waters.” Whales that find themselves in the North Sea have been seen to panic, thrash about, head in the exact wrong direction, and get so confused that they end up beaching even when escape is possible. Imagine a group of people who are hiking and lose their way, only to get separated, and then die alone in the wildness.

A sperm whale devouring a squid, 1873.
A sperm whale devouring a squid, 1873. Internet Archive/ Public Domain

For many years scientists have been trying to figure out why these beachings happen. They have considered the role of pollution or human-generated noise, though neither explains the historical cases. One study in 2007 found a correlation between warmer periods and the frequency of North Sea strandings. There was a long gap in mass strandings between the 18th century and the 20th century, and it may be that they happen with more frequency now because the whale population is recovering from decades of intensive hunting.

An intriguing theory that has been around in some form since at least the 1980s, implicates the activity of the Sun. Whales keep their bearings through echolocation, but like many other animals that travel far and wide, they also use magnetic fields to navigate. Geomagnetic lines can act as trails of sorts, which guide animals over long distances. But those paths are not entirely reliable, since natural variation in the make-up of the Earth can cause anomalies and weak spots in the otherwise regular magnetic lines. And, on occasion, when a strong solar storm hits the planet, the magnetic field can go a little haywire.

Vanselow, of the University of Kiel, first became interested in sperm whale strandings in the late 1990s, and in his research, he came across a chart showing solar activity over the past few centuries. The curve, he noticed, looked a lot like the curve of sperm whale strandings over the same period. He started looking for connections between the phenomena, and found … pigeons.

A 1602 engraving of a beached whale in the Netherlands.
A 1602 engraving of a beached whale in the Netherlands. Public Domain

Pigeon racing is an old sport, but its modern incarnation took off in the 19th century. Trained homing pigeons all start from the same point and race each other home. For much of the way, they navigate by magnetic field, and in the 1970s a team of researchers showed that during solar storms, the birds were less likely to make it home and took longer to make the journey. “Pigeons for races are very expensive, so a loss of them is a bitter loss,” says Vanselow. Pigeon racers rely on forecasts of solar storms to decide whether to fly their pigeons, especially in more northern latitudes, where the effects of solar storms can be stronger.

Once he made this connection, Vanselow thought he could be on the right track. In 2005, he and a colleague published a paper that found a correlation between strandings and solar cycles. In a follow-up paper in 2009, he looked to a different measurement of solar activity, a global geomagnetic index. These papers showed that, in general, sperm whale strandings could be associated with solar cycles, though not everyone was ready to draw that connection. The authors of the 2007 paper that connected warmer temperatures and whale strandings found that solar behavior had no impact on their findings.

In this new paper, however, Vanselow and his colleagues considered the cause of the strandings in January and February of 2016. They obtained data on geomagnetic conditions around the North Sea from the closest measuring station they could find, in Solund, Norway. Those readings show that, not long before January, when whales started stranding in the southern part of the North Sea, the magnetic field in its northern reaches had changed.

Composite image of a solar flare, 2012.
Composite image of a solar flare, 2012. NASA Goddard Space Flight Center/ CC BY 2.0

The North Sea is not the only place in the world where whales beach themselves, and mass stranding are more common elsewhere. In Cape Cod, where a spit of land hooks into the ocean to form a bay, where full moon tides can pull the water out a mile, there are multiple mass strandings every year. In New Zealand strandings happen with similar frequency, and single events can involve hundreds of whales. This doesn’t just happen to sperm whales, either. One of the largest known mass strandings involved 337 sei whales stuck on a beach in Chile in 2015, and last year 600 pilot whales were stranded in the shallows of New Zealand’s South Island.

The cause of these other strandings is just as mysterious as it is in the North Sea. They also have long histories, so while some recent stranding incidents have been linked to human interference, in general this is considered an natural phenomenon, unexplained.

“The ongoing question we always have is—why is this happening?” says Katie Moore, the program director for animal rescue at the International Fund for Animal Welfare (IFAW). In the two decades that she’s worked on marine mammal strandings, she’s heard anecdotal reports that stranded animals had followed prey into Cape Cod Bay, but necropsies show that these animals often have empty stomachs. She knows that, in her area, full moons mean trouble. Cape Cod resembles New Zealand in its shallow, silty waters, and some research indicates that whales may have difficulty echolocating in such waters.

Beached pilot whales in Cape Cod, 1902. Mass strandings happen there multiple times a year.
Beached pilot whales in Cape Cod, 1902. Mass strandings happen there multiple times a year. Public Domain

But going back more than a decade now, she and her colleagues have, like Vanselow, been interested in the idea that solar storms might play a role. During a chance encounter with an old friend, Moore learned that the Bureau of Ocean Energy Management had been talking to colleagues at NASA about the connection, too, and needed to a partner organization with data on whale strandings. Moore’s group, IFAW, and the government agencies have decided to bring their data sets together.

The results of that work have yet to be published, but it’s unlikely to show that solar storms are the one and only explanation for whale strandings. Antti Pulkkinen, the NASA scientist working with Moore’s group, thinks that, while a solar storm could contribute to whale strandings, “we need harder evidence to prove the connection. And that is what we aim to provide.”

Their research seems to be painting a complicated picture. “When we weren’t seeing what we thought we might see,” says Moore, “we started bringing in some other oceanographic experts to bring in other layers. Is it the weather? What directly or indirectly is driving the animals into shore? That’s where I think the real answers will come in, in pushing past space weather and looking at bigger picture of oceanographic change.”

A sperm whale on the beach at Hunstanton, on the east coast of England, 2016.
A sperm whale on the beach at Hunstanton, on the east coast of England, 2016. Richard Humphrey/ CC BY-SA 2.0

If every whale stranding has multiple causes, at least in some cases solar storms may be the dominant one. Vanselow’s new work suggests that the late December magnetic disruption was large enough to disorient the whales. It is circumstantial evidence, but more convincing than a general theory. Vanselow’s work “convinces me that it is plausible in this case,” says Graham Pierce, lead author of the 2007 paper. But he adds, “If it had been generally true there should have been a stronger relationship with sunspots and strandings in the historical series.”

For the whales to be led astray by the geomagnetic changes he identified, Vanselow says, they “must be at the wrong place at the wrong time”—at an oceanic crossroads, where a wrong turn can lead to death, just at the time a solar storm hits. For these unfortunate sperm whales, a gaseous burp from a flaming orb some 92 million miles away may have been enough to seal their fate.