While sharks on cocaine sounds like a clumsy Jaws-Scarface crossover, some researchers say the idea may not be as wacky as it sounds—especially in the waters off Florida. There sharks in a diverse assemblage swim along a major drug-smuggling throughway, which potentially exposes the toothy predators to floating bundles of narcotics. “This is the only place in the world where a shark could come into contact with such massive doses of cocaine,” says Tom Hird, a marine biologist and broadcaster based in England.
Hird explores the plausibility of sharks ingesting narcotics in a new television special called Cocaine Sharks, which is part of Discovery’s annual Shark Week. The eye-catching title is an homage to Cocaine Bear, a recent film about a black bear going on a cocaine-fueled rampage. Though the movie is very loosely based on a real event in 1985 (in which a bear died shortly after ingesting several containers of cocaine that had been dropped from a plane over northern Georgia), Hird thinks the chance of sharks encountering the drug is much higher than it is for most other predators—including bears. “I fully believe that it’s real, especially with the amount of cocaine that is washing up” in Florida, Hird says. “And that's just the stuff that makes it to the beach. It doesn’t include the stuff that gets caught out at sea.” Because cocaine is soluble in water, he says, a shark swimming in the vicinity of a damaged package could theoretically get a contact high.
To test the hypothesis, Hird teamed up with Tracy Fanara, an environmental scientist at the University of Florida, who studies how human pollutants impact sharks and other marine life. “Living in Florida for the past 20 years, I’ve heard so many stories about these cocaine bales washing ashore,” Fanara says. “For that reason, I went from laughing at the idea to being fully onboard” with investigating whether sharks were consuming such drugs.
The team focused on the waters around the Florida Keys, a string of islands just south of the Florida peninsula. Typically, drug smugglers drop their stash from lightweight aircraft south of the Florida Keys, probably for boats to pick up. And thanks to ocean currents, some of those drugs often wash up around the keys. According to news reports, a boater there fished out a load of cocaine weighing 62 pounds on July 2, only weeks after the U.S. Coast Guard confiscated more than 14,100 pounds of cocaine (worth an estimated $186 million) that was being smuggled through the Caribbean to Florida. And in January $2.3 million worth of the drug washed up in the Florida Keys and was turned over to the U.S. Border Patrol.
The keys’ balmy waters are also a hotspot for sharks. Several species swim here, including tiger sharks, hammerheads and bull sharks. Hird and Fanara jumped in the water near the keys with several sharks to see whether they could observe anything fishy about the animals’ behavior.
In one instance, a normally wary great hammerhead shark (Sphyrna mokarran) swam toward the divers. This species, which can grow up to 20 feet long and weigh well more than 500 pounds, leaned to one side as it swam, making the normally graceful shark look unusually wobbly. Because sharks’ streamlined body help them effortlessly slice through the water, any snag in their movement is easy to spot. “It’s almost like noticing that someone graffitied the Mona Lisa,” Hird says. The divers also observed a sandbar shark (Carcharhinus plumbeus) swimming in small circles as if fixated on an imaginary object—another behavior the researchers found odd. But they couldn’t link these behaviors to cocaine exposure.
Back on the boat, the team dropped dummy bales of cocaine into the water next to fake swans to see which object the sharks preferred. To their surprise, several sharks ignored the swans and swam straight for the dummy bales. Some sharks even took bites out of them. Next, the researchers dropped bait balls filled with concentrated fish powder into the water. According to Hird, this powder is known to trigger a dopamine hit in the shark’s brain. In this case, the bait caused a stir in the sharks, similar to how catnip riles up felines. The researchers hoped the sharks would associate this stimulation with the “cocaine.” Finally, the team again deposited fake bales into the water, but this time they did it from airplanes to simulate a drug drop scenario. Several sharks swam over to investigate the splashdown, which Hird says sounds a little bit like a struggling fish would to a shark.
While the researchers think these tests suggest a shark would be tempted to take an exploratory nip out of a cocaine bale, not all shark researchers are taking the bait. Gavin Naylor, director of the Florida Program for Shark Research at the University of Florida, agrees it is plausible for a swimming shark to bump into floating narcotics around Florida. He thinks sharks are much more likely to treat these bales like driftwood or other inedible detritus than a tasty meal, however. “These are predators,” says Naylor, who was not involved in the television program. “Unless the bale was laced with freshly killed fish, it’s unlikely they're going to want to eat anything that is not living.”
Though bales of actual cocaine did wash up on the keys while the team observed the sharks, Fanara notes that it is impossible to conclusively tie any of the animals’ behaviors to ingesting cocaine without an in-depth study. This would require capturing the sharks, collecting blood samples and sifting for chemical traces of cocaine back in the laboratory.
Pinpointing traces of cocaine in a shark’s blood would be the first step, but further work is also needed to understand how the drug would impact the fish’s neural wiring. Although researchers have yet to give a shark an experimental whiff of cocaine, they have conducted studies on how the drug impacts other fish. In 2016 scientists in Switzerland examined the effects of cocaine on zebra fish, a type of striped minnow commonly used in scientific experiments. The researchers were surprised to find that most of the cocaine accumulated in the fish’s eyes instead of their brain. Some zebra fish eyes contained concentrations of cocaine that were 1,000 times higher than levels that would be lethal to humans.
The Swiss scientists were also surprised to find that instead of revving up the zebra fish, the cocaine suppressed their movements. “You’d think that a shark on cocaine is going to be swimming around all over the place at 1,000 miles an hour,” Hird says. “But that is us taking our human brains and putting it into the shark’s head.”
In whatever way cocaine may affect sharks, recent research illustrates that aquatic animals can involuntarily fall under the influence of narcotics. In 2021 a team studying the impact of methamphetamine pollution on brown trout found that in the lab, the fish appeared to become hooked by only small amounts of meth in the water. They even exhibited signs of withdrawal when moved to a new tank.
The team hopes Cocaine Sharks raises public awareness of the impact that drugs, including pharmaceuticals, can have on marine life. “This is a catchy title to shed light on a real problem,” Fanara says.
Naylor agrees that Shark Week offers a large platform. But he thinks highlighting “outrageous” scenarios misses the point. “The natural world has so many mysteries that we don't understand,” Naylor says. “Why we have to generate artificial constructs to get attention is beyond me.”