Gore is something certain people are drawn to on the big screen, but an ocean full of blood has got to be a horrifying real-life situation.  Before 1916 and the first episode of shark terror in New Jersey, the notion of a man-eating fish had not even entered anyone's mind.  Today, shark attacks -- particularly those by Carcharodon carcharias, better known as the great white and whose Latin name derives from "jagged tooth" -- have become a popular horror-film and TV news topic, sometimes used to perk up an otherwise boring summer.

Andrea Lynch, Florida 2007
Andrea Lynch of Florida, 2007
attacked by a bull shark
Todd Endris, California 2008

Surfer bitten by a great white
Todd Endris's story was featured in
the July 2008 issue of
Reader's Digest
(click to enlarge)

Watch YouTube video

 

White shark frontal view

White sharks are famous
for their estimated 3000
self-replacing serrated teeth

White sharks are intelligent.  They are also problem solvers, not just ravenous eating machines as Hollywood lore depicts them.  Yes, they have multiple rows of replacement teeth and they are apex predators with no known enemies, but they are also powerful and majestic and sensitive, as well as being a kind of natural housekeeping force for the marine world.

They frequent seas and oceans where water temperatures range from 54dF to 75dF (12C - 24C), but are known to venture inland along tributaries in search of their prey.  (Their large mass enables them to briefly sustain the effects of fresh water, with the inlet tidal exchange of fresh and salt water helping as well.)  The very first famous "killer shark" of 1916, featured in an August 2001 Reader's Digest headliner titled "Jaws: The Prequel," made its way a mile and a half up the Matawan Creek with the ocean tide, where it came upon a swimming hole and a bevy of boys.  (Read story here.)

Preferring to feed on marine mammals once they grow toward maturity (12 feet plus), white sharks are frequently found in coastal shallows where seals, sea lions and elephant seals provide their primary source of fuel.  Although classified as a "pelagic" or open-ocean fish, whites tend to concentrate near the coasts of Australia, California, South Africa, the northeastern United States, New Zealand and around the Mediterranean.


White shark jaw with extra teeth Great white tooth

Architecture of the jaw of a great
white with its rows of replacement
snap-up teeth

Click on single tooth to enlarge
Visit www.jawshark.com for more


The famous documentary Blue Water, White Death tells the story of a film crew that sought great whites in what is known as "the deep."  All they found were oceanic white tip sharks, now nearly gone thanks to years of rampant over-fishing.  Still, the sight of divers leaving their cages and their tireless attempts to capture close-up footage makes this documentary a shark-lover's classic.  In the end, guess where they find Carcharodon carcharias, their coveted prize?  Near Australia's Great Barrier Reef, in the coastal shallows, where food is always found.  (Order DVD here.)

In this video by Eric Cheng, watch tiger and bull sharks feeding in the Bahamas.  Notice the nictating membrane that passes over the shark's eye for protection as it hunts.





Great Whites and other sharks are radar experts, thanks to a profusion of electroreceptors in the form of tiny jelly-filled black dots in their noses and heads that enable them to sense electromagnetic fields generated by living creatures around them.  These dots are known as the ampullae of Lorenzini -- sensitive to one half of a billionth of a volt (source Wikipedia).  A white shark's sensors are accurate enough to detect the beating of a human heart.

Ampullae of Lorenzini Shark electroreceptors
Ampullae of Lorenzini

A white shark's nose is only used for scenting.  To breathe, whites filter oxygen from the water through their gill slits.  As it swims, the shark moves its head from side to side, literally forcing water through its nose and smelling what's around it in the ocean.

A great white's warm-bloodedness allows it the working muscles to hunt other warm-blooded mammals like seals and sea lions.  In the need to convert mammalian fat to squalene (shark liver oil), its digestive system does not fare well on muscle, gristle and bone.  The plumper the prey, the better.  The legend of the hungry shark that hasn't eaten for weeks derives from a white shark's search for the food that serves it best -- the whiskered pinniped, fattened from basking on rocks and the beach.

Seal with shark bite
This seal survived an attack by a great white
(Click to enlarge)

Just as white sharks frequent coastal shallows in search of seals and sea lions, their feeding patterns tend to follow the activity of their prey.  Seals are early morning surface-water "fishers" themselves.  White sharks will cruise the shadowy bottom, camouflaged in its depths by their dark gray coloring, and scout for seals hunting at the surface.  The entire ocean is busily catching -- all the way down the food chain.


The movie Jaws terrified the masses who sat before the big screen, their adrenaline pumped by the trademark musical theme.  But Carcharodon carcharias does not normally rip swimmers to pieces, sneaking up from beneath them with its giant gaping mouth and beady eyes.  Yes, its serrated teeth are backed up with rows of replacements for those that break off.  Yes, a shark tosses its head from side to side, tearing off its victim's flesh.  And yes, it will circle and scope and come back once it has made its plan.  All this is part of its nature, and we are at its mercy when we are in its world.

SoCal coastBy the year 2000, 80% of America's population had moved to within an hour's drive of the coast.  More people than ever before now live closer to the ocean, and in their unfamiliarity with it, do not realize that it is truly a different realm.  The ocean operates on hierarchy, expediency and opportunity.  Small fish hustle to escape bigger fish, birds swoop down from the air to catch prey, and marine mammals flop off rocks to feed themselves.  Schooling (herding) keeps the odds of getting nailed much lower, which is why swimmers are advised to venture out in groups or pairs.

There are shark sightings and shark attacks.  Sightings can consist of a glimpse of a dorsal or tail fin, a vision of a shape beneath you in the water, or an actual encounter.  Many encounters involve sharks that come closer for inspection or a look-see and then swim away.  There are millions and millions of sharks in the ocean.  And the ocean is enormous.  Don't expect a shark to know what a human being is.  They have the right to take a look, just as you like to see them on TV or in aquariums at the zoo.

Chatham MA shark
 Shark tagged in Chatham, Mass.
September 2009

Shark encounters are non-violent.  A shark may cruise closer to or circle the object of its interest, its movement slow and leisurely.  But that may only be Part 1.  Once a shark decides to strike, it summons up enormous speed, usually hurtling upward from the murky sea bottom.  This is how sharks hunt seals who play around at the surface -- spotting them from below and moving in fast.  However, the vast majority of shark encounters result in the shark swimming away.  In fact, the entire number of shark attacks in the 20th century (that's 100 years) on the West Coast of the US was only 108, with only 8 incidents being fatal.  Think about the numbers of car accidents and dog bites that we risk just walking about in our ordinary world ... those statistics are much, much higher.

Shark attacks are generally considered to be provoked or unprovoked.  "Provoking" means aggression or some action on the part of the human to engage the shark.  If a shark pursues a human without having been engaged in some way and a strike ensues ... well, there you have an "unprovoked" shark attack.

New terms for shark attacks have been popularized by the media in recent years: hit and run, bump and bite and the sneak attack However, with built-in inferences, these terms may be more dramatic than accurate.  Researchers in the field of shark/human interactions prefer a different set of terms: mistaken identity, investigation and a territorial or displacement attack.

When sharks attack humans, the five species most often involved are the great white, the tiger shark, the bull shark, the sand tiger and the oceanic white tip.

Bull shark
Bull shark
Oceanic white tip shark
Oceanic white tip shark
Tiger shark
Tiger shark

Mistaken Identity

This is also classified as a predatory attack, in which the shark strikes a human, "discovers" that its victim is not a preferred type of prey, and then lets go.  Swimmers and surfers in black wetsuits, as well as the shape of a surfboard seen from below (especially if backlit by sunlight) may cause a shark to "mistake" someone or something for a pinniped (seal or sea lion) and go after it.  Two thirds of people struck by a shark don't even see it.  Most shark attacks occur in shallow water and may be prompted by curiosity or aggression.  The attempt to feed is considered "predatory."  Many people, however, are merely grazed by sharks, whose skin is hard and abrasive, leaving welts that bleed.

Peter Benchley, in his excellent book Shark Life, reminds us that simply by entering the water we are notifying its inhabitants that we are there.  Sharks are not fools.  But humans, in their media-fed concept of nature, believe animals to be cuddly, furry and fun.  "Before you enter the water, stand for a moment and look at the sea around you.  Are there birds working offshore -- swooping and diving into a school of baitfish near the surface?  That's a sign that larger predators are underneath, driving the baitfish upward."

This is not bad advice.  There are days that one simply does not want to go into the ocean -- its texture different somehow, maybe darker, more whirly and ominous.  Trust your senses.   I remember swimming on a churny gray day with a friend.  We were half a mile off shore, and there was a thick red tide.  I could barely make out my arm in front of my face.  But he suddenly called out, "Whoa!  Silver bellies, two of them!  Did you see?  They came up right underneath us."  We had no choice but to keep swimming, whatever [they] were, and I was glad I hadn't seen a thing.

White Shark, Isla GuadalupeThere are upwards of 350 species of sharks, out of which only about 25 have been known to attack humans.  And the five that make the short list have only done so on very rare occasions.  While sharks have rods and cones like we do in eyes that can see underwater, they may not know what you are in low or dim light.  Andrea Lynch (see photo above) was bitten at night, and Dave Martin of Solana Beach very early in the morning.  Still, most shark attacks occur between 1 and 4 in the afternoon, within 50 feet of shore, in less than 5 feet of water, on weekdays, and in calm conditions.  Why?  Because that's when and where most people are likely to be in the ocean!  (Do sharks care about weekdays?  No.)

Investigation

Sharks may circle an object of interest or come closer and give it a bump.  This is a form of investigation on the part of the shark, which doesn't have hands with which to reach out and touch an object or pick it up (obviously).  If the bump or the circling (scoping the scene) is inconclusive, the shark may decide to take a trial bite -- even a gentle bite.  Unfortunately, the size and sharpness of its teeth may result in serious wounds to a human being, despite the shark letting go and swimming away.  As soon as their teeth register bone, muscle and gristle, sharks know immediately that a human is not a seal.  In search of energy (fat) to support their body temperature, they are looking for particular kinds of food.  But in murky water or low light, they may not be able to tell what exactly is nearby in the water.

The Territorial Attack

Shark warning signThis is an aggressive act, with the intent to "displace" or clear the area of an intrusion perceived as a threat.  Having made its decision to attack, the shark may drop to the bottom and hurl itself upward at its victim with enormous speed.  The attack may be carried out in a series of deep and vicious bites.  The serial bite is known as a "repurchasing bite," involving repetition, with no tearing of flesh, the goal being to kill.  The 2008 fatality at Solana Beach on Dave Martin was a displacement attack, with only one swimmer having seen the shark as it circled once and returned to take action.

Shark-encounter stories, when shared and retold, are an exaggerator's dream.  Things look bigger in the water anyway, and when you have lived to tell the tale your relief can make its dimensions swell.  Amazingly, the nefarious film Jaws only showed hints of "the shark," due to hellish unforeseen problems with the mechanical sharks designed for it, and the result was even more audience tension, which might be why so many people's experience of the ocean changed forever after seeing it.  Less is more, and if your imagination by itself can terrorize you without props or reality, then you have been worked, as they say.  (Click here for more on the filming of Jaws.)

There are tiny sharks and huge sharks, common sharks and rare sharks, aggressive sharks and meek sharks ... but the word alone elicits respect from most people, who seem to regard anyone who has seen a shark as a kind of mystical figure.  The first shark I was lucky enough to see in its entirety (besides leopard sharks congregating over the sandy bottom in La Jolla, and a few small sand sharks that hustle away as soon as they see your ankles in the shallows) was what had to be a small megamouth cruising the bottom.  I kid you not.  This is said to be the rarest kind of shark in the world, first seen in 1976 by sailors off Hawaii (it was caught in an anchor).  A krill feeder, its big head confused me and when I tried to describe it, lifeguards told me I must have seen a whale. Insulted, I knew it was not, but had no way of identifying what I had seen except by way of Google ...


Megamouth shark Megamouth head

Megamouth shark


In August 2013, Discovery Channel's Shark Week aired footage of a megamouth, and here it is for your viewing pleasure: