Shark attacks: Every swimmer's worst fear
A recent surge in shark attacks has caused alarm. What's going on?
How common are attacks? They're extremely rare. Over the course of a typical calendar year, the U.S. sees about 30 to 40 unprovoked shark attacks, with one fatality. This year has seen an uptick: Through the first half of 2015, 23 attacks have occurred, one of which killed a 65-year-old woman snorkeling off the Hawaiian island of Maui. But what's striking this year is that many encounters have taken place farther north than usual. Florida, with its balmy temperatures and 1,300 miles of coastline, is usually the location of most U.S. shark attacks, and true to form, 11 have occurred in the Sunshine State this year. But North Carolina, which normally experiences one or two attacks a year, saw seven in a three-week span in June and July — including separate attacks an hour apart on a 12-year-old girl and 16-year-old boy, who each lost an arm.
Why the spike in North Carolina? A perfect storm of conditions, starting with the weather. Most attacks in North Carolina take place at the height of summer, when ocean temperatures reach about 80 degrees. But a late-spring heat wave warmed the sea earlier than usual, drawing sharks up from the south — and sending higher numbers of people to the state's beaches. Another factor is North Carolina's extended drought, which means less rainwater has flowed into the ocean, making the coastal waters higher in salinity — which sharks like. Finally, some of the victims, including the boy and girl who lost arms, were swimming near fishing areas. Bait — especially bloody fish parts called chum — can serve as a real shark magnet. Sometimes sharks are chasing bait or fish, says University of North Carolina shark biologist Frank J. Schwartz, and "someone just gets in the way."
Do sharks like to eat humans? Despite a murderous reputation enshrined in the public consciousness by the Jaws franchise, sharks actually have little interest in human flesh. Of some 480 shark species, only a handful — notably the great white, bull, and tiger — are known to attack people, and when they do it's generally a case of mistaken identity: In murky waters sharks sometimes confuse humans with their usual prey, particularly seals. When they bite people, sharks generally release them and swim off in search of more satiating targets — nerve endings on their serrated teeth can differentiate between calorie-rich seal blubber and a skimpier human meal. "Sharks don't eat humans, they spit out humans," says Peter Klimley, an animal behaviorist at the University of California at Davis. "Humans aren't nutritious enough to be worth the effort." Since the first recorded shark attack, in 1580, fewer than 2,800 unprovoked attacks and 498 fatalities have been confirmed throughout the world. If you take a dip in the ocean, there is just a 1 in 11.5 million chance you'll get bitten by a shark. You're far more likely to be struck dead by lightning (1 in 700,000).
But aren't attacks on the rise? Yes, they've grown steadily more frequent in recent decades, largely as a consequence of population growth — there are simply more people in the water. "We're an instigator of these interactions by intruding into their aquatic turf," says George H. Burgess, director of the Florida Program for Shark Research. Most attacks take place in shark havens such as Hawaii and the Caribbean, as well as Australia and South Africa. Last week, a surfer competing in an event in South Africa fought off a shark that attacked him on live TV. Surfers and other board-sport enthusiasts suffer about 60 percent of attacks, because sharks frequent the surf zone, where the warm waters provide a rich menu of fish.
How do you avoid shark attacks? First, remember you're in the sharks' house — at a huge disadvantage. Sharks have a "sixth sense": Through tiny pores peppering their snouts, they detect when electrical fields are even slightly disturbed by a heartbeat or muscle twitch. With that in mind, here are some helpful hints: Don't swim after twilight, which is feeding time, or with an open wound — some sharks can smell a drop of blood 3 miles away. Try to stay in groups, because sharks tend to target lone individuals. Don't stray too far from shore, and be wary of sandbars or steep drop-offs, both shark hangouts. Never wear shiny jewelry, which sharks sometimes mistake for shimmering fish scales.
What do you do if attacked? Usually, you will have no chance to respond. "The overwhelming majority of attacks are hit-and-run," says University of Miami marine biologist David Shiffman. "The shark bites you and is gone before you even know it." But if the assailant lingers, don't thrash around or scream, which may provoke another bite. If possible, try smacking the shark on the snout, ideally with an inanimate object, which often drives it away. Failing that, keep fighting and claw at its sensitive eyes and gills. "One should not act passively if under attack," Burgess says. "Sharks respect size and power."
The Jaws effect By a strange twist, the recent surge in U.S. shark attacks coincides with the 40th-anniversary re-release of Steven Spielberg's 1975 blockbuster, Jaws. From its opening sequence — when a swimmer feels a tug on her leg, scored by ominous bass notes — the film aroused in audiences worldwide a primal terror of getting eaten alive. More than 20 feet long, with 300 serrated teeth, the great white became one of cinema's iconic villains — turning the species into a coveted real-life target for trophy seekers. "An average Joe could catch a big fish, and there was no remorse, since there was this mindset that they were man-killers," says Burgess. He estimates that commercial and sport fishing have reduced the number of large sharks of all species by more than 50 percent — and some by as much as 90 percent. While fewer than 500 people have died from shark attacks over the past 500 years, humans kill an estimated 100 million sharks a year.