If you haven’t read the first part of this article, do so now!
Everybody knows that sharks are powerful hunters, but how much have you been told that’s fact, and how much has come from a Hollywood backlot? Below are some of the most common “facts” surrounding sharks, along with an explanation on how they measure up to reality.
Sharks are a high risk encounter in the ocean
Since the advent of media featuring sharks as a central antagonist (think Jaws, Deep Blue Sea, and upcoming The Shallows), people’s fears of sharks have ballooned. With the news that 2015 had the highest amount of shark attacks in recorded history, these fears might even seem justified. Fortunately, things are not quite as scary as they appear.
Like plane crashes, earthquakes, and acts of terror, shark attacks are treated like a disaster. As such, almost every fatal shark attack gets reported on, because these stories get views for media outlets.
While this can be good for viewership, it leads to a bias among viewers that these attacks occur with more frequency than they actually do. This is a similar phenomenon to seeing a cockroach in your house: the idea that when you see one, you can assume that there are 100 out of sight. Unfortunately, this natural human bias does not really hold up for shark attacks.
In fact, when you consider all the things you do before even taking a dip at the beach, worrying about being killed by a shark begins to look ridiculous. That car ride to the beach? 33, 000 deaths a year. That hamburger you ate at the beach café? Heart disease from sources including obesity and high cholesterol levels kill over 600,000 people a year.
If I still haven’t convinced that you don’t have much to fear from sharks, maybe this Daily Show clip will sway you.
Sharks actively hunt humans
This one gets tossed around a lot, usually accompanied by the similar “sharks can grow addicted to the taste of humans”. These are relics of the Rogue Shark Theory (something I may cover at a later time), and are proven false with a quick biology lesson.
Peter Klimley, an animal behavioralist at the University of California, attests that the shark’s own digestion gets in the way of it branching out its diet. He says that “Great whites have extremely slow digestive tracts; if they eat something less than optimal, it slows down their digestive tract for days, prohibiting them from eating other things”.
Klimley attributes shark digestive structure, to why large species tend to gravitate to animals with higher fat content. Fat contains “twice the calories of muscle”, and these calories are mandatory for the shark “to maintain its body temperature and keep its brain warm in cold water”.
Because of this, unless a large shark is starving or unhealthy, there are no incentives for it to peruse a thin, bony human.
On the flip side, the tiger shark has been found to be less discriminating in its diet, most likely as a survival strategy to survive harsh times. When swimming in waters where tiger sharks are known to dwell, more caution is needed.
Sharks can detect a drop of blood in a swimming pool
Now before you freak out, like most “true” rumors surrounding sharks, there is a big asterisk next to this statement.
To begin with, consider the size of your standard private swimming pool.
Now consider the size of all the oceans combined.
As you can see, you and a shark would have to be in the same swimming pool chunk of the ocean for it to detect anything, which is unlikely to say the least.
Even if you were close enough to a shark where it could potentially detect the blood, it would not guarantee interest. This is due to a property of lamellae, organs that sharks use to “sniff” out their surroundings. Llamellae detect amino acids, compounds found in high qualities in the blood of prey.
However, amino acids also float freely in the ocean. To combat this abundance of info, shark brains have certain filters that reduce all the unneeded scents their llamellae pick up. This makes sense, as otherwise sharks couldn’t differentiate prey scents from all the “white noise” in the environment, making them poor predators.
As was seen in the previous section, the vast majority of sharks are picky eaters. Therefore, it is highly likely that any given shark will be filtering out any scent signals it receives from a bleeding human, in favor of amino acids that announce more tasty prey.
Sharks need to swim to avoid drowning
Really, the truth of this statement depends completely on the species of shark. Website Live Science writes that whether a shark needs to swim or not depends on how it respirates. Sharks that are not active swimmers, such as the wobbegong, can force water over their gills while not moving. This method is called buccal pumping.
Active swimmers such as the great white and the whale shark, use ram ventilation. Simply put, these sharks swim with their mouth open, which causes water to pass over their gills, giving them oxygen. It is these sharks that need to keep swimming, as without water passing over their gills, they would drown.
Of course, some sharks do a mixture of both types of breathing, like the tiger shark. To do this, these sharks have two small openings on the sides of their heads, called spiracles. These spiracles act as mini pumps, drawing in water while the shark rests on the ground.
While scientists agree that sharks that use ram ventilation need to constantly swim, they question how these sharks act when they need to rest. The assumption has been that they “sleep” while they swim, but surprisingly, this behavior hasn’t been observed for a lot of species. In fact, the white shark was caught “sleeping” for the first time just recently, the video of which you can see here.
Keeping it Real
All in all, when dealing with the shark, it is important to separate the fact from the fiction. If we don’t, fear of the animals places them in legitimate danger. When we consider a shark as nothing much more than a monster, we turn a blind eye to damaging practices such as finning and aggressive sport fishing.
If you learned something new from this article, please share it with friends, family, and colleagues. If more people understand that shark are no monsters, we can have a conversation on safe and responsible ways to inhabit their environment. With your help, we can insure that shark populations continue to make a comeback, all while keeping the public happy and informed.
Castro, J. “Must Sharks Keep Swimming to Stay Alive?” Live Science. 28 May 2013 2013. Web. <http://www.livescience.com/34777-sharks-keep-swimming-or-die.html>.
Great White Naps for First Time on Camera. Anonymous Discovery, 2016. Video.
Hile, J. “Great White Shark Attacks: Defanging the Myths.” National Geographic. 23 Jan. 2004 2004. Web. <http://news.nationalgeographic.com/news/2004/01/0123_040123_tvgreatwhiteshark.html>.
Powell, D. “Shark Smell Myth Found Fishy.” Inside Science. 2010. Web. <https://www.insidescience.org/content/shark-smell-myth-found-fishy/1151>.
I Know what You did Last Summer of the Shark. Dir. Stewart, J. Prod. Stewart J. Perf. Stewart, J. Comedy Central, 2002. Video.
Xu, J., et al. Deaths: Final Data for 2013. Georgia: Center for Disease Control and Prevention, 2016. Print.