art by Sarah Burns
The Science of Sharks: Public Perception and its Alignment with Reality
by Nathaniel Briggs
Why are humans so fascinated with sharks? Even though attacks on humans occur rarely, and fatal attacks are even rarer, we seem to have an intense fear and fixation with them. Last year’s eight attacks along the Outer Banks of North Carolina continued to spark interest in the matter, and it does not seem like we will become bored with sharks anytime soon. Just ask Discovery Channel, whose 2015 edition of “Shark Week” averaged their best Nielsen viewership rating since the program’s inception in 1988. Why are so many captivated by these seemingly silent, yet awe-inspiring creatures?
A Brief History of Our Fishy Fondness
Australian clinical psychologists Brian Tuckfield and Jason Encel claim, “Our intense fear of sharks is primal instinct. We are wired to fear any animal that could eat us. Shark attacks really tap into very primal fears. A fight or flight response is set off.” Is it true that we are just innately afraid of larger animals, or are other factors at play? Why do these attacks occur, and what can we do as a species to protect ourselves? Have the incidents of shark attacks really been increasing or are we simply overreacting? Perhaps it would be prudent to first examine how shark attacks became a topic of concern for us.
The integration of these apex predators as a large component of our cultural conscience is a relatively recent phenomenon. Juliet Eilperin, an author and reporter for the Washington Post, states in her book, “Demon Fish” that sharks were a topic that captured little interest until the 20th century. In medieval times, noblemen would show off shark teeth by trying to claim they were actually dragon “tongue stones,” an infinitely more fascinating claim for humans at the time.
From the 15th through 17th century, there was a slight resurgence in shark interest from the augmented level of maritime travel. However, prior to the 1930s, scientists did not consider sharks to be a danger to an uninjured human. Subsequently, attacks on Navy crewmembers during World War II, and movies such as “Jaws,” have given ways to increased public interest in the matter, along with sensationalist media coverage of such attacks. Has this love affair also been caused by an increase in shark attacks? Let us examine some of the statistics.
Humans have identified roughly 400 species of sharks in the world’s oceans, only three of which have been responsible for the majority of recorded shark attacks: the great white, bull, and tiger shark. Since the beginning of the 20th century, there have been a total of 5,034 reported shark attacks worldwide, 22.7 percent of which were fatal. Although the rate of shark attacks per decade has increased, there has also been a large increase in the amount of people spending time in the water. “It’s important for the public to really understand shark attacks in terms of risk,” states Sal Jorgensen, a great white shark researcher at the Monterey Bay Aquarium in California. From 1950-2013 in California, for example, the number of shark attacks per year increased from 0.9 to 1.5. Meanwhile, the amount of beachgoers saw a 211 percent increase in that same period, 53 million to 165 million. This means the chances of being bitten by a shark in California decreased 91 percent over the past 63 years.
If anything, sharks have more reason to be worried more about us. Commercial overfishing through the past several decades has decimated shark populations in United States waters by as much as 80 percent since the 1970s. This decrease is very similar in other regions of the world as well. Sharks are particularly vulnerable to excessive fishing due to their low birth rates, coupled with a slow growth and maturation period.
Considering the decrease in the probability of experiencing a shark attack, one would think society should not be so enamored with them. After all, coconuts, champagne corks and cows are responsible for more deaths per year than sharks, yet no one seems to be clamoring about them. Could the source of our obsession be that we find the physiology of sharks to be larger than life?
Super Shark Sensing
The tools sharks are equipped with are, indeed, compelling. Take their eyes, for example. We once thought that sharks had poor vision, but that misconception is starting to change. Shark eyes are very similar to humans’ except for one important difference: a standard pair of shark eyes comes with what is referred to as the tapetum lucidum. This is a layer of tissue located behind the shark’s retina, the part of the eye which detects light. The tapetum lucidum reflects light back through onto the retina a second time, potentially increasing its sensitivity to light 10 times greater than humans’. This part of the eye is responsible for the glowing in a cat’s eyes at night, as well as other backyard creatures’ like raccoons and opossums.
The shark’s sense of smell is also quite impressive, as they can detect one part blood for every millions parts of water! Their hearing is similarly astounding, being able to detect frequencies lower than 375 hertz — one and a half octaves lower than the lowest note on a piano.
Finally, sharks possess one novel capability that humans do not: an ability to detect others’ electrical signals. Sharks have a set of organs called the ampullae of Lorenzini, a type of electroreceptor to aid with this. The structure begin at pores throughout fishes’ bodies and lead to polysaccharide mucus channels, which translate stimuli from the environment to the electrical signals to be sent to the shark’s brain. Not only can sharks detect the electrical activity from the nervous system of their prey, they can also use the ampullae to detect changes in the environment such as salinity, temperature and pH.
With such an impressive arsenal of abilities, it is easy to see how one could fear sharks and why one might think that sharks would attack more frequently. Simply put, however, sharks do not care much for humans. They do not consider us to have a high enough fat content to meet their metabolic demands, and many attacks seem to be a result of mistaken identity. Sharks attacks like this are often “hit-and-run” cases where the shark will take a test bite, realize the prey is not worth the energy, and then swim away. Another reason for shark attacks is their perception of humans as threats. Some sharks can become quite territorial and will fear a stranger encroaching on its turf. As in the 2015 Outer Bank attacks, some environmental factors, such as high ocean salinity due to low rainfall and changes in wind patterns, could push the shark’s territory closer to the shore where humans often play.
Now, as you gear up for your future beach trips, what are some precautions you can take to lessen the likelihood of a shark attack? The National Oceanic and Atmospheric Administration (NOAA) has a few suggestions:
1. Always stay in groups since sharks are more likely to attack an individual. Do not wander too far from shore --- this isolates you and decreases your chance of being rescued.
2. Avoid being in the water early in the morning and during darkness or twilight hours when sharks are most active and searching for food.
3. Do not enter the water if bleeding.
4. Avoid wearing shiny jewelry because the reflected light resembles the sheen of fish scales.
5. Avoid waters being used by sport or commercial fisherman, especially if there are signs of bait fishes or feeding activity. Diving seabirds are good indicators of such action.
6. Use extra caution when waters are murky and avoid bright colored clothing--sharks see contrast particularly well. Refrain from excess splashing.
7. Exercise caution when occupying the area between sandbars or near steep drop-offs--these are favorite hangouts for sharks.
8. Do not enter the water if sharks are known to be present and evacuate the water if sharks are seen while there. And do not approach a shark if you see one.
9. Between the months of May-September, restrict your ocean swimming from 9 AM-5PM.
Abiding by these simple rules can decrease your already small probability of being attacked by a shark.
If sharks rarely attack us, should they still be intensely feared? I would not say so. One important thing we need to realize is that sharks have been evolving in the ocean over millions of years. It is largely their habitat. When we enter the ocean, we sign an unwritten contract to respect their territory whether we know it or not. We cannot blame sharks for simply doing what they have been doing throughout their whole existence, nor can we justify wiping them out for our species’ safety. As a matter of fact, sharks play key roles in the marine ecosystem. A decrease in shark population could significantly affect the mechanics of aquatic food chain. Just like any other species of life, we need to respect sharks. We have our own niches and so do they. So, let us awe in their magnificence and power, but realize that we must also be cautious, conscientious and respectful.