Sharks are insane. There’s no light way around it. Almost everything about their natural history, their morphology, and their adaptations seem to cross the line from typical, run-of-the-mill animal nature to completely and utterly bizarre.
Let’s start with their sensory organs. Since childhood, it is ingrained in us that there are five general categories of senses: sight, smell, taste, hearing, and touch. Each of these senses has a general organ associated with it for people: eyes for sight, nose for smell, so on and so forth. Five general sensory organs for five general senses. Pretty simple stuff, pretty well established across the animal kingdom. I mean, wouldn’t it be ridiculous for other animals to have extra senses that we don’t have? That would be utterly terrifying.
Sharks don’t have five sensory organs. Not six, either. Their sensory organ count tops out at seven. Seven separate body parts, each performing a different function – usually related to food consumption, further cementing their reputation as incredibly efficient killing machines.
Their sixth sense derives from something that all fish (including sharks) share: a lateral line. This line is a series of sensory organs running alongside the fish, giving it the sense of motion detection. This way the fish can feel potential prey moving away from it – or a fearsome predator moving towards it – before it actually sees the animal at hand. The fish in the Chondricthyes class (sharks, rays, and chimaeras) have a seventh sense as well: the ampullae of Lorenzini, a series of snout receptors that can detect electrical impulses produced by otherwise cryptic prey.
I could go on all day about all the anatomy that we take for granted in the animal kingdom that are simply not true for sharks. Skeletons are made out of bones, right? Not for sharks – their entire skeletal structure is made out of spongy cartilage and connective tissue. It’s also pretty much common sense that fish lay eggs. Sharks can lay eggs. But for most, this egg laying occurs inside the mother’s body, where the pups are incubated, hatch, and are then born into the water. (Some species forgo the whole egg concept and give live birth.) And as for jaw placement? The whole idea that jaws are attached to something on the head just simply doesn’t apply to these guys.
Who needs cranial jaw attachment? Not goblin sharks, that’s for sure! (Photo credit Peter Halasz)
In general, sharks also have way too many of certain body parts, as the following chart suggests.
|Body Part||Our Number||Shark’s Number||Because . . .|
|Eyelids||2 per eye (top and bottom)||3 per eye, including a clear nictitating membrane||…sharks need eye protection underwater.|
|Teeth||28, 32 if you still have your wisdom teeth||3,000 at a time, thousands in a lifetime||…a sea creature diet isn’t as easy on the teeth as our mushy human food.|
|Male reproductive organs||1 per male||2 per male||…sharks are just more manly than human men.|
Last week, I encountered what some might consider the most unabashedly bizarre shark of all – a scalloped hammerhead shark. Not only does it have a detachable jaw, spew live babies like some kind of mammal wannabe, and can find electricity with it’s snout, but it also has one of the oddest shaped heads in the animal kingdom.
Scalloped hammerheads are just one of 9 species in the genus Sphyrna, which derives from the Greek word for hammer and refers to the odd head shape. This “hammer” is known as a cephalofoil, and this oddity has been around in the shark world for 20 to 25 million years.
Why the odd shape? There are many theories floating out there, but one widely accepted idea is that the odd eyeball placement enhances the animal’s binocular vision. Monocular vision, or using one eye at a time to increase the field of view, is better for animals that are primarily prey, as it helps them scan the horizon quickly for predators. Binocular vision, however, offers much more of an advantage for predatory critters. This is because the binocular vision, which creates an overlap between the two eyes, helps the animal locate and focus on specific prey items. The wider the head, the greater the binocular overlap – as long as the eyes tilt forward, as the hammerheads’ eyes do. Hammerheads also have 360 degree vision, thanks to their straight-outta-sci-fi eyeball placement. Like sharks needed something else to make them scarier.
Hammerheads, like many big sharks, have built up a rather nasty, human-biting reputation. After all, most of them are primarily carnivorous beasts the length of a Lincoln Navigator, so it’s not hard to imagine where that reputation came from. This reputation however, is almost 100% unfounded, according to the International Shark Attack File. Since 1580, only 1 fatal hammerhead attack has been recorded. That’s right. We’re looking at a 1 per 500 year average. Overall, the grand total of fatal, unprovoked shark attacks in the last 500 years? 138, out of just barely more than 1,200 reported attacks. Those are pretty good odds.
Now I’m not suggesting that we go out and give hammerheads a big ol’ bear hug, of course. Sharks still have powerful jaws and thousands of sharp teeth. They are still creatures that have the potential to hurt us. But that’s it – just the potential.
Humans are not natural prey of sharks. Most cases of shark bites end up being “exploratory bites.” One taste usually results in the shark leaving, because people are apparently not as tasty as seals, stingrays, squids, or any one of the million other things that sharks eat.
Sharks are a group of animals that people should certainly be aware of and respect. This is just a classic example of the “we leave them alone, they leave us alone” concept. So exercise caution, but don’t go thrashing about in terror like a wounded animal if you come across one. Observe, learn, and share. Because sharks may be some of the weirdest animals to grace our oceans, but they’re also some of the coolest.