'Shark vs Surfer': Why do the predators attack humans when we aren't their favorite food?
Sharks are terrifying predators of the ocean, but often, their attacks on humans go uncompleted in that they don't actually eat the humans. The reason for this is that humans don't offer sharks the high-fat content that they need for sustaining their large muscular bodies. Surfers are most likely to be attacked. When a shark sees a human paddling on a surf board, it mistakes the human and the surf board to be one of its favorite foods — the sea lion. Once the shark bites into the human and realizes that it is not what it was expecting, it usually swims off.
While one of the biggest fears when going into the ocean for a swim is a shark attack, in reality, more humans die by drowning than a shark attack. Perhaps much of this fear could be placed on Steven Spielberg's iconic 1975 film, 'Jaws'. In 1916, five human deaths in New Jersey were attributed to a shark, but today, those reports are being disputed.
In the majority of recorded attacks, the shark bites the victim, hangs on for a few seconds (possibly dragging the victim through the water or under the surface), and then lets go. It is very rare for a shark to make repeated attacks and actually feed on a human victim. The shark is simply mistaking a human for something it usually eats. Once the shark gets a taste, it realizes that this isn't its usual food and it lets go.
Attacks have also frequently occurred when humans were spearfishing in ocean waters. Sharks are attracted to dying fish — the smell of blood in the water and the electrical impulses given off as the fish struggles. These signals can be detected by sharks with their ampullae of Lorenzini, a set of "magnetic detectors" under the skin on a shark's snout. The ampullae are electrically sensitive cells that connect to the skin's surface through small tubes. Once a shark arrives on the scene, it may become agitated and aggressive in the presence of so much food. A hungry, excited shark can easily mistake a human for its usual prey.
Sometimes, the cause of a shark attack is simple to determine. The shark is responding to human aggression. Nurse sharks, for example, are generally placid fish that lie still along the bottom of the ocean floor. For some reason, this makes some divers think that it's a good idea to pull their tails. Irritated nurse sharks have taught several divers to keep their hands to themselves. For this reason, shark attack statistics are divided between provoked and unprovoked attacks.
There are a few ways to avoid shark attacks with the most obvious precaution being to avoid beaches that are known to be infested by sharks. Swimmers are also cautioned not to swim in muddy, brackish waters near the mouths of rivers, especially in murky waters. Additionally, don't swim with open cuts. Even a small amount of blood in the water can attract sharks from miles away. Don't swim when a shark's natural prey is present in large numbers. If you are swimming near marine mammals or other shark prey species and you see them react with sudden alarm and flee the area, follow their example.
'Shark vs Surfer' airs on National Geographic on August 2 at 8/7c. An encore presentation will air on Nat Geo WILD on August 13 at 9/8c.