When Douglas McCauley was a kid, it was uncommon for him to see a shark when he was surfing or swimming in the waters of Southern California. “It would make the nightly news if someone spotted a white shark,” he says.
But just a few decades later, the coastline began welcoming new inhabitants. When McCauley, a biologist at the University of California Santa Barabara, started dropping off his own kids for surf camp at a popular beach near the university, he spotted fins just outside the surf—some tiny, and some not-so-tiny.
Throughout the 20th century, sharks faced environmental threats and struggled to survive. McCauley felt a flood of mixed emotions seeing them swim nearby. “As a shark biologist, it was amazing and exciting to see these signs of ocean health,” he says. “But as a parent, I needed to understand what was going on out there.”
In 2020, McCauley tasked his lab to start counting and categorizing white sharks spotted along the beach. The goal was to create a forecast—what McCauley calls a ‘sharkcast’—that could be texted to the caregivers bringing kids to the water each day. That resulting work, now a research program, called SharkEye, sends emails and texts to people interested in shark conditions along Santa Barbara’s Padaro Beach.
McCauley and his lab are one of a handful of U.S. research groups trying to predict where and when sharks are likely to be found along the coast.
It’s a timely ambition. Since the mid-1990s, shark population numbers have been rebounding, driven by strict federal and state conservation laws and warming ocean temperatures in both the Pacific and Atlantic. At the same time, more people are recreating in coastal waters. And this year’s super El Niño climate patterns have brought predictions of a sharky summer season.
“What we're most scared of is what we don't know,” says McCauley. “More information helps us constructively confront some of this fear of sharks, but most importantly, it helps us plan the same way the weather helps us plan for our day at the beach."
The tools needed to create a ‘sharkcast’
McCauley’s lab uses automated drones that fly a mile straight out from the shore and back, at the same time each day, to count sharks and determine their size using AI. McCauley says the texts go to camps, lifeguards, and local shop owners—all who have a stake in knowing what’s in the water. The system is accurate for sharks near the surface in the survey zone or sharks that have been tagged in the past, but it can miss sharks deeper in the water or when the ocean is turbulent.
At other labs, scientists have tagged sharks with acoustic transmitters that ping like cars going through a tollbooth. Projects tracking juvenile white sharks have been ongoing for decades and use tags, buoys, and drones to monitor where they swim up the coast of California from their nursery in Mexico.
(Divers recently spotted a great white shark in the Mediterranean. See the video here.)
But predicting sharks’ presence like a weather forecast is still a challenge. While some biological events—like the date of leaves turning red in the autumn or when the grunion will flop onto beaches—are predictable, shark behavior is intricate. “They're not simple fish,” says McCauley. “They have a lot of complexity to their behavior and natural history."
Temperature is one factor scientists consider when forecasting sharks. Small sharks tend to congregate near the surface and close to the coast. Like little humans, they can’t stay warm easily and are sensitive to getting cold. For white sharks on the West Coast, they stick around when water temperatures are between 60°F and 80°F. Sharks also respond to changes in salinity, storms, and the movements of their prey.
Chris Lowe, who runs California State University Long Beach’s Shark Lab and helped create SharkEye with McCauley, points out that humans have been forecasting weather for hundreds of years, and methods for doing the same with sharks are still developing. Even with ample data and technology, he notes, weather forecasts can still be wrong.
And unlike a current of air or a cloud, individual sharks have minds of their own.
(Learn how scientists are creating protected marine havens for sharks.)
Getting inside the mind of a shark
New technology is improving forecasts by giving scientists more clues about shark behavior. Megan Winton, a scientist with the Atlantic White Shark Conservancy, uses bio-logging camera tags that are “basically like giving a smartphone to a shark.” The tags allow her to see where a shark's attention is pointed. Her research has contributed to an app created by the conservancy called Sharktivity, which delivers real-time information of shark sightings and movement data.
Winton’s research shows individual sharks have unique habits and behaviors. She has watched as sharks were startled by birds or a seal popping up in front of them. The camera tags also let her observe a shark feasting on a seal and then resting at the bottom of the ocean: the shark equivalent of a food coma. "Individual sharks have different vibes,” she says. “Some are more cautious, some are a little bit bolder, and it's really fascinating."
Years of data from both coasts indicate where sharks should be in certain areas, but that doesn’t necessarily mean an individual shark will be there at a certain time. “Sharks aren't that different from people,” Lowe says. “There's a bulk of the population that fall within this norm, and then you've got individuals on the fringes."
Individual sharks have different vibes. Some are more cautious, some are a little bit bolder, and it's really fascinating.Megan Winton, Atlantic White Shark Conservancy scientist
And when sharks are detected along a stretch of beach, it’s not clear when they present a threat. Lowe’s lab has gathered drone footage and acoustic pings from years of tracking sharks, which shows that sharks and humans are very often in close proximity. And when humans are in the water, sharks don’t seem fazed.
"We thought people would just be a nuisance to the sharks, and now we realize that people don't matter. We're flotsam, really,” he says. "We probably don't smell like food; we don't sound like food. We don't chase them, so we don't pose a threat. They just ignore us."
When shark interactions do occur, scientists think it’s probably due to a mix-up: white sharks mistaking a surfboard for the bottom of a seal, their preferred prey.
White sharks are probably the best‑studied shark in the world, Lowe points out, but scientists still don't know where they mate or give birth. And one big mystery Winton points out: "We still really don't know why sharks occasionally bite people."
(How scientists are trying to save the hammerhead shark from extinction.)
Learning how to live with ocean predators
On Padaro Beach near Santa Barbara, California, camps full of kids get the alerts that McCauley sends out, and camp leaders can decide when it’s a sharky day, he says. Some days, the drones count 15 sharks. "On days when things are sharky with large sharks, they switch to play more beach volleyball than they do being in the water."
In the next decade, the complex picture and predictions of where sharks will be, and when they will be there will likely become much crisper. McCauley says that he could easily envision drones atop lifeguard towers across the country, constantly doing shark surveillance. That would offer both immediate insight and create a forecast for that particular beach.
“They could tell you what they expect the shark weather will be like the rest of the week, and perhaps even into next week."
As sharks face fewer threats and more prey, the odds of people sharing coastline with sharks may be increasing.
McCauley says forecasting tools are part of humans learning to live with the predators they’re trying to protect. “The whole goal of this science is to make sure that we continue sharing these waters safely."
