Meet Simon and Jekyll, two great white sharks on a 4,000-mile journey together. Are they … friends?

Slowly, a great white shark swims toward the boat and onto a specialized hydraulic lift. Lured in by bait, the shark’s mouth is hooked, and it is encouraged to swim to the boat like “teaching a dog to walk on a leash,” says Bob Hueter, the chief scientist at OCEARCH, a nonprofit that specializes in shark tracking. 

Once the shark is lifted onto the boat, "it's like a pit crew in an auto race," Hueter says. One scientist ventilates the shark by putting a hose of cool seawater into its mouth, while another attaches a tail rope to prevent the animal from hurting itself. In about 15 minutes, the research team performs about a dozen procedures, including measuring the shark, running ultrasound scans, and taking blood, muscle, semen, and fecal samples for various research projects.

The work is part of OCEARCH’s efforts to study great whites in the western North Atlantic, a less well-researched population than others around the world. "Here we are at the location of Jaws, and yet we didn't really know the animals as well as we should," Hueter says.

Two juvenile great whites tagged in this way, Simon and Jekyll, recently became famous thanks to a social media post that pointed out the pair had been traveling together for 4,000 miles up the North American Atlantic coast. People began to wonder if the sharks might be friends—but the situation is not so simple.

“Friendship implies an emotional connection. That's not what this is about,” says Yannis Papastamatiou, a biologist at Florida International University who is not involved in the project. “Sharks don't form any emotional bonds with each other. Most animals don't.”

These sharks may not be “friends,” but there are no previous records of two sharks traveling together for such a long period, leading scientists to wonder what this could reveal about the mysteries of shark migration.

The strange case of Simon and Jekyll

The two juvenile males—each between 10 and 15 years old and over eight feet long—were first tagged off the coast of Georgia in December 2022. The tags transmit data via satellite when one of the sharks surfaces, allowing researchers and the public to follow the animals’ movements online in real-time.

In the spring, sharks migrate to summer foraging grounds. Salvador Jorgensen, a marine ecologist at California State University, explains that the sharks he studies in the eastern Pacific travel to and from “the white shark cafe”—a remote spot in the Pacific Ocean between Baja California and Hawaii with plentiful fish and squid—at slightly different times. “Many males execute very similar migratory routes and cycles, but travel separately,” Jorgensen says.

When Simon and Jekyll reached Long Island, researchers noticed their tracks were remarkably similar. Then they arrived in Novia Scotia "within practically the same day,” says Hueter—odd behavior for great whites. “We sat up and said: What's going on here?"

Although this was a one-time event, such a similar route for the two sharks over a long time and distance is significant. “It's not like you're just taking one quick snapshot,” Papastamatiou explains. “If you were driving your car, and another car was 200 meters behind you all the way from Florida to New York, you're traveling together.”

Social sharks?

Great whites are traditionally viewed as solitary, but researchers believe they may display some social behaviors like other shark species.

Because fish don’t display obvious caring behaviors, such as grooming or looking after young, researchers determine social bonds by measuring whether individuals spend more time together than they would by chance. One study found the associations formed by white sharks are not coincidence, while another found that they may remain close while hunting to benefit from food scraps after a kill.

“Surprisingly, we see more and more that white sharks might fit into that social category,” Papastamatiou says. If something similar were happening with Simon and Jekyll, “this would be the first time we would have evidence of [white sharks] actually traveling to these sites together.”

Jorgensen thinks there may be other reasons the pair followed the same route. “Are these two sharks following similar environmental cues and instinctual impulses, which could lead to parallel movements?” he wonders.

Heuter explains that sharks are guided by factors such as seawater temperatures, the amount of light each day, and the location of hotspots for certain kinds of prey. They’ve also traveled these routes before, “so they know the road,” he says.

Blood brothers?

Another possibility remains. The researchers are currently running genetic tests to find out whether Simon and Jekyll are related.

“If I was a betting man, the smart money would be that they're not siblings, that this is just a very unusually synchronized, almost coincidental juxtaposition of these animals as they follow the normal run to the north,” Heuter says.

However, if the results do reveal Simon and Jekyll are brothers, it could “revolutionize the perspective on sibling relationships in these animals,” he adds. “This really makes us stop and think about the genetic basis of these migratory movements.”

Even if they are related, the sharks may not necessarily be traveling together. They could both simply be following similar instincts. “More closely related individuals might have greater similarity in their innate migratory clock and compass,” suggests Jorgensen.

Whether or not Simon and Jekyll are intentionally sticking together, their common route is revealing new secrets of how these apex predators prowl the seas.