Are There Megalodons Still Alive in the Mariana Trench?

It’s a nightmare scenario: megalodons, prehistoric sharks nearly as large as blue whales, survive in the deepest part of the ocean, the Mariana Trench. Somehow, they make their way to the surface and become the terror of every creature on the high seas . . . including humanity. Science fiction books and films have explored these kinds of scenarios, but how likely are they, really?

What Were Megalodons?

The scientific name of the megalodon is Otodus megalodon, which simply means “big tooth.” It was the largest shark to have ever stalked the ocean. Scientists believe the largest of them may have been up to 82 feet long, though the average was probably more like 58 feet in length. This is still much, much larger than the biggest great white shark, which measured only about twenty feet, and approached the size of a full-grown blue whale at 69 feet!

Not a lot is known for sure about megalodons since their bodies, being mainly cartilage, aren’t found in the fossil record. Instead, we mainly find jaws and teeth – some measuring 6 inches or more! Some baby and juvenile megalodon teeth were found off of the coast of Panama in shallow waters, and this was probably a kind of nursery where young megalodons could feast on smaller fish without worrying about getting caught themselves by larger fish. As adults, megalodons hunted larger prey such as whales, dolphins, porpoises, sea turtles, and pretty much whatever they wanted to eat. Fortunately for us, the last megalodon went extinct anywhere from 2.5-3.5 million years ago . . . or did it?

What Does the Mariana Trench Hide?

The Mariana Trench, named after the nearby Mariana Islands in the Pacific Ocean south of Japan, is the deepest trench in any of the world’s oceans. Discovered in 1875 by the British ship H.M.S. Challenger, the trench has been a fascinating mystery to scientists ever since. It’s over 1,500 miles long and about forty miles wide. Most shockingly, at its deepest point, it is almost seven miles down to the bottom! That means if you could pick up Mount Everest and drop it into the Mariana Trench, you’d still have to swim down about a mile before you would reach the peak of the mountain! Only two people have ever reached the deepest portion of the trench, using specialized equipment to withstand the immense pressure and cold. That slow, careful voyage took five hours.

The bottom of the trench is so far down, absolutely no sunlight can penetrate the pitch darkness. The temperature hovers just a few degrees above freezing. And the pressure from the vast weight of the water pressing in from all sides is over 1,000 times the atmospheric pressure level at sea level. Surprisingly, researchers discovered not only microbial life but some species of fish and other marine organisms able to survive at this depth. Unfortunately, they also discovered human pollutants such as microplastics, candy wrappers, traces of pesticides banned in the 1970s, and higher-than-normal radioactivity from Pacific nuclear tests.

Could Megalodons Survive in the Mariana Trench?

So could megalodons somehow have survived from prehistoric times and still be lurking in the Mariana Trench today? The short answer is no. And here’s why:

• Megalodons were warm-water creatures. In fact, paleontologists believe a cooling period that froze the ocean in areas where megalodon pups matured may have been the primary reason for their demise. The deep ocean is too cold for them to survive.
• Megalodons were extremely large animals that ate other extremely large animals. Nothing big enough or numerous enough to sustain them lives in the Mariana Trench.
• If megalodons were leaving the trench to hunt whales and such and then going back to hide there for some reason, we would see evidence of it in bite marks on whales and other large animals, as well as thousands of freshly lost megalodon teeth on the ocean floor.
• For a species to survive and multiply there must be a breeding population at least in the hundreds to provide the necessary genetic diversity for species survival. Such a large number of megalodons could not go unnoticed.
• Another reason scientists surmise megalodons may have gone extinct is that great white sharks, which hunted in the same biomes, were better genetically adapted to the environment. Great white sharks are decreasing in population and thought to number only around 3,500 individuals today. It would be surprising if the less competitive megalodon were somehow able to thrive in a modern world that is far less conducive to sharks than the prehistoric world was.

What Would We Do if We Did Discover a Living Megalodon?

It’s a captivating “what if” scenario that really is the realm of science fiction, but isn’t it fun to speculate: what would we do if we did discover a megalodon in the Mariana Trench? There are all sorts of options:

• Leave it alone and never go there again!
• Study it without disturbing it so it doesn’t go on a round-the-world rampage.
• Find some way to cordon off a region of the ocean for it that it couldn’t possibly escape. (A massive saltwater lagoon of some sort?)
• Kill it to make sure giant prehistoric carnivores never menace the earth again.
• Definitely, whichever option we choose, we have to monetize it, right? Put its picture on lunch boxes and such in the gift shop. You know the routine.

Beyond this tongue-in-cheek thought experiment, this question raises interesting issues of how humans manage known, living wildlife that may be challenging for human populations and the ecosystem in other parts of the world. Feral hogs or invasive pythons in the United States for example. Disease-bearing mosquitos in Africa. Overpopulated rabbits in Australia. To what extent do we let nature take its own course, and to what extent do we intervene, especially if our previous interventions have helped cause the problem? Maybe, in the end, when we think about the ocean, we should worry less about megalodons that definitely aren’t in the Mariana Trench and more about the microplastics that definitely are.

So What Does Live in the Mariana Trench?

The most common life forms living in the deep waters of the Mariana Trench are xenophyophores, multinucleate unicellular organisms found on the ocean floor throughout the world’s oceans; amphipods, which are shrimp-like crustaceans; and holothurians, which are small sea cucumbers that are also found on the sea floor worldwide. Other sea creatures found at this depth tend to be really different and are named as if life there is a perpetual Halloween. They include:

Ghost snailfish: Recently discovered, so “Ghost” is just a nickname. Marine biologists will have to catch a sample to determine a scientific name. There are about 360 species of snailfish, but this one is unique in shape and size, at six inches long.

The Barreleye Fish or Spookfish, which has a transparent head.

The Dumbo Octopus, which is about 8-12 inches long and gets its name from Dumbo the elephant.

The Goblin Shark or Vampire Shark, which is a living fossil because this species has existed for millions of years without change.

The photo featured at the top of this post is © Warpaint/Shutterstock.com