Scientists have learned much about the day-to-day lives of sharks in recent years, but much about them remains a mystery. Many species live in deep waters far from shore and migrate long distances, making it hard to observe them. As top predators, sharks are fewer in numbers relative to their prey. They mature slowly and reproduce less often than many ocean creatures, so catching them in the act, so to speak, isn’t easy. Pop culture often fills in the scientific blanks on its own, but, not surprisingly, sometimes gets it wrong. In honor of 2016's Shark Week, we debunk some common myths about sharks inspired by movies, celebrities, and other non-scientific sources.
Sharks stalk people.
“That is absurd, complete Hollywood lunacy,” says explorer, filmmaker, and ocean advocate Philippe Cousteau, whose show Nuclear Sharks airs on Thursday on Discovery during Shark Week. Sharks aren’t going to wait around for someone hanging on a buoy, says Greg Stunz, director of the Center for Sportfish Science and Conservation at Harte Research Institute for Gulf of Mexico Studies in Texas. “A shark will lose interest pretty quickly and move on looking for other prey.”
If sharks were really that interested in us, a lot of people would know it, adds Nick Whitney, manager of the Behavioral Ecology and Physiology Program at Florida’s Mote Marine Laboratory. “Humans would be such an easy meal. We’re terrible swimmers, awkward and splashing around, and pretty defenseless. There is no evidence whatsoever to support the idea that sharks stalk people.”
When sharks do bite humans, it typically is out of curiosity — biting is one way they decide what something is — or to defend themselves. Out of more than 470 shark species, in fact, only four have been involved in fatal, unprovoked attacks on humans: great white, oceanic whitetip, tiger, and bull sharks.
Sharks are drawn to human blood.
Sharks possess very refined sensory receptors and can famously detect a drop of blood in the amount of water filling an Olympic-sized swimming pool. But that little cut on your finger is insignificant in relation to everything else in the ocean.
“They are very sensitive to blood, but not attracted to human blood any more than any other kind,” says Cousteau. Nor, he adds, can they necessarily zero in on the source of blood when they do detect it without additional cues such as a struggling animal or other predators feeding.
“The ocean is full of all kinds of smells and scents,” says Whitney. “Swimming in the ocean with a cut is not a good idea for other reasons, but not because it will attract sharks.” (One of those reasons is bacteria, including Vibrio vulnificus, better known as flesh-eating bacteria.)
Shark attacks are on the rise.
First off, consider use of the word attack. An actual shark attack, says the Global Shark Attack File, is extremely rare, even less likely than statistics would have us believe. A shark bites a surfboard and leaves the surfer unharmed, and the incident is recorded as an "attack." Collisions between humans and sharks in murky water also get recorded as "attacks.” Some attacks are provoked — a fisherman trying to land a shark, a diver poking one with a spear — and the shark should get a pass.
Second, incidents tend to increase along with the human population and the number of people going into the ocean. “Year after year, more and more people are in the water, millions more, yet the number of bites remains relatively steady,” Cousteau points out. “I would argue that attacks are going down in relation to the number of people in the water. The fact that we’re killing 100 million sharks a year for soup probably has something to do with it.”
Third, almost any incident involving a shark today becomes big news. Twenty years ago, a non-life-threatening shark bite made local news and went no further. “Today, everyone has a cell phone and videos go viral, and if CNN has a slow news day, it ends up on national news,” Whitney says.
Statistically, shark attacks are not on the rise. The Attack File recorded, in 2015, 110 unprovoked, confirmed shark attacks worldwide, 9 of them fatal; in 2014, 92 attacks, 6 fatal; and in 2013, 105 attacks, 13 fatal. As of June 18, 2016, 44 attacks, with a total of four of them fatal, have been recorded. Bottom line, there are many other things people should be more worried about.
Sharks will eat anything.
“People have found all kinds of random things in the stomachs of tiger sharks, for example,” says Whitney. “But a lot of times, even they are very selective. For some of our studies, we’re trying to catch great white sharks, and it’s amazing how finicky they can be about taking the bait.”
Most sharks are carnivorous, eating squid, fish, crustaceans, and marine mammals. Different species definitely show preference for their typical food source, says Cousteau. Great whites, for example, prefer sea lions or other prey with a lot of blubber. Basking sharks, whale sharks, and megamouth sharks filter feed on plankton and the occasional small marine creature.
Sharks have feeding grounds.
Certain areas with abundant prey definitely seem to attract sharks. One example is a seal colony off of Cape Cod that brings in great whites every summer, but Whitney says tagging data show they don’t actually spend a lot of time there. Stunz notes that some species follow prey around; blacktips follow bait fish, for example, and hammerheads follow tarpon. High-energy predators, sharks tend to move around a lot, moving through feeding areas rather than hanging out in them.
Certainly sharks are not patrolling a specific territory ready to attack anything that wanders into it. “Think of lions on the African savannah,” Cousteau says. “If you wander into a herd of antelope and start running around, you might be setting yourself up for failure. In the same way, surfing or swimming in an area with sea lions increases your likelihood of encountering a shark.”
Mythology aside, sharks play an important role in ocean ecosystems. “When we remove these apex predators, it can cause things to go out of balance,” says Stunz. “Shark populations are decreasing worldwide due to overfishing and other threats, and that reverberates throughout the ecosystems they inhabit.”