7 days ago
- Science
- National Geographic
This animal has a built-in taser to stun sharks
Researchers have documented Gulf torpedo rays (Torpedo sinuspersici) using electric shocks to deter large sharks. Photograph by Andy Murch, Nature Picture Library
Electric rays are staying out of the stomachs of sharks by shocking them—with up to 200 volts.
With powerful jaws and high levels of resistance to toxins, big-bodied sharks such as tiger sharks and great whites can eat just about anything. Sea snakes venomous enough to kill a human with one bite and stingrays armed with six-inch spines are light snacks for these apex predators of the ocean.
Scientists have long believed that no marine creature is safe from a large, hungry shark, but at least one group of animals has evolved an effective means of evading shark digestion: electric rays.
In a study published last month in the journal Ethology, researchers found that electric rays can scare away both tiger and white sharks by zapping them with powerful electric discharges. While electric rays are known to use their built-in tasers for hunting, this is the first study to show that they also use them for self-defense.
"I wouldn't have initially thought that the electric discharge these animals produce would be that effective as a deterrent against predators. But now I'm quite convinced that it may be a very effective defense,' says Yannis Papastamatiou, an ecologist at Florida International University who studies sharks and other marine predators and led the new analysis. A shocking power
Found in temperate and tropical oceans around the world, most electric rays measure less than three feet long. But some, like the Atlantic Torpedo Ray, can grow up to six feet (1.8 meters) and weigh up to 200 lbs (90 kg).
The largest among these rays can produce electric discharges over 200 volts, which is more than enough to knock a human off their feet. When stimulated by the rays' nervous system, kidney-shaped organs on either side of their head release charged ions—usually to zap a smaller animal for dinner. Magazine for all ages starting at $25/year
(Want to learn more about rays? Here are five fun facts.)
Electric rays are also known for not shying away from people and large sharks, says Papastamatiou, who is also a National Geographic Explorer. 'Generally, if you're that bold, it's because you're pretty confident in your defensive capabilities," he says.
Papastamatiou saw their boldness on full display for the first time while studying great white shark feeding behavior off the coast of Mexico's Guadalupe Island in 2018. He and his colleagues had attached cameras to the dorsal fins of six sharks.
In one video, a great white shark approached a Pacific electric ray in the water column. As the shark got within striking distance, the ray appeared to cup its pectoral fins, the posture it typically assumes when zapping its prey.
'The shark suddenly went ballistic and shot up,' recalls Papastamatiou. 'Something had really disturbed it." Two minutes later, the shark returned, but this time it swam right past the ray, perhaps having learned its lesson.
All sharks have a unique sensory system that allows them to detect the weak electrical fields produced by living organisms. That makes them extremely sensitive to electricity. But sharks' tendency to eat anything—despite the danger—made the researchers skeptical that what they'd seen might be a coincidence.
Then in 2024, a scuba diving instructor named Ali Ansaar captured a similar scene in Fuvahmulah, Maldives, between a Gulf torpedo ray and a tiger shark. This footage, Papastamatiou says, convinced him that what he'd seen wasn't a fluke. Diver Ali Ansaar filmed a Gulf torpedo ray warding off a tiger shark in the Maldives.
As part of this study, Papastamatiou and his colleagues re-examined past footage, including an experiment they had conducted in the late 1990s on Pacific electric rays off Palos Verdes, California, and found more examples of the behavior. To observe the differences between predatory and defensive zaps, the team had either offered the Pacific rays freshly speared fish or prodded them on the back with a rod. The rays emitted similarly strong electrical discharges in response to both stimuli, but the poking elicited shorter and more rapid discharges.
"If they're doing it for defensive reasons, it makes sense to put out one very quick blast,' says Papastamatiou. 'These animals essentially have a battery, and like any battery, it takes a while to recharge." Lessons in shark deterrence
Because this study only involved Pacific electric rays and Gulf torpedo rays, more work is needed to determine if all electric rays are capable of deterring large sharks. The ability of an electric ray to send a shark packing likely depends on its size, says Dave Ebert, a shark scientist at San Jose State University who was not involved with the study.
Ebert has found other species of torpedo rays in the bellies of big sharks. 'I think if they're [small enough] sharks can probably eat them,' he says. Small or juvenile rays may not produce enough electricity to deter sharks, while a zap from a larger ray might be enough to escape their jaws—literally. Ebert has also seen torpedo rays sporting big shark bites. 'You could tell from the bite mark that the shark let go.'
The study's authors believe their findings not only change what we know about the defensive capabilities of electric rays but also add credence to the idea that zapping large sharks with electric currents is an effective means of deterring them—a lesson that could help humans design better methods to keep sharks away, too.
(Here's how to stay safe if you're swimming with sharks.)
But more than anything, the behavior suggests that electric rays are not to be underestimated. "Electric rays can pack a punch,' says Ebert. 'They generally don't attack, but if you tease them, they will stun you."
