It’s possible that I may have missed shark week.
I figure an article about the largest and most famous prehistoric shark – Megalodon, the 15-meter whale killer – may be enough to redeem myself. While I’ve talked about Megalodon before, I feel that I didn’t spend enough time on why Megalodon went extinct. We know with certainty that it went extinct towards the end of the Pliocene Epoch – approximately 3 million years ago – despite what some iffy Shark Week content will tell you. On the other hand, how they went extinct has been subject to debate within the paleontological community. In this article, I will discuss some theories regarding Megalodon’s extinction and identify which are most plausible.
Theory #1: An Ice Age Conundrum
When Megalodon went extinct at the end of the Pliocene, something profound was happening in the world. Beginning in the Miocene Epoch some fifteen million years ago, Earth underwent a gradual cooling process. By the end of the Pliocene, a multitude of factors had transformed this cooling process into a full-fledged ice age. As glaciers formed across Northern continents, global temperatures – in both land and in the sea – plummeted.
While it’s been assumed that such a drop in oceanic temperatures was disastrous for Megalodon, new research may prove otherwise. A study from March 2022 examined global size trends of Megalodon and discovered that larger individuals lived at higher latitudes in cooler waters[i]. If this is accurate, then Megalodon may have followed Bergmann’s rule: the biological concept that states animals at higher latitudes grow larger than those at lower ones to better accommodate the cold.
One thing to note is that this may have been true for the Miocene Epoch, but not the Pliocene. As global temperatures descended further, it may have still proven too much for Megalodon to cope with. However, it seems that climate change alone would not have been enough to force Megalodon into extinction.
Theory #2: Where has all the Prey gone?
Living alongside a 15-meter-long shark would not have been a safe environment. For Megalodon, anything it came across was on the menu, whether that be smaller prey like seals or larger organisms like whales. Smaller baleen whales appeared to have been favourites, with fossil evidence of attacks being preserved in Peru[ii] and Venezuela[iii]. A whale fossil from the Eastern United States even shows signs of healing[iv], meaning it survived getting bitten in the chest!
Yet their reliance on large prey may have contributed to their downfall. The end of the Pliocene saw a massive dip in the diversity of large marine animals (mammals, sharks, turtles, seabirds), with some 36% of species going extinct before the Pleistocene[v] (2.6 million years ago). Whales went through a particularly rough phase, with a substantial decrease in diversity at the start of the Pliocene[vi]. The ones that did survive were mostly the enormous species we find today, which may indicate their size protected them from Megalodon. Without their favourite prey in abundance, Megalodon may have been more susceptible to extinction.
Theory #3: The New Killers on the Block
Have you ever had a new neighbour move in and ruin your vibe? Well, that’s what may have happened to Megalodon when a handful of rambunctious predators appeared on the scene.
The first of these killers were giant odontocetes, predatory toothed whales closely related to the living Sperm Whale. The most famous was Livyatan, a 15-meter predator that appeared in the mid-Miocene, about 10 million years ago. A fellow whale-eater, Livyatan fossils are found in the same locations as Megalodon, meaning that the two likely competed for the rights to a nice morsel of whale. Though Megalodon outlived Livyatan, the threat of new killers displacing Megalodon persisted through the Miocene and into the Pliocene.
Enter Carcharodon carcharias, better known by its common name: the Great White Shark. The most famous and recognizable of sharks (for better and worse), Great Whites first appeared during the Late Miocene alongside Megalodon, and soon provided fierce competition. Studies on tooth enamel of Pliocene Great Whites and Meg’s revealed the two had similar ecological roles[vii]. Perhaps more interesting is that Megalodon’s diet transitioned throughout the Miocene and into the Pliocene[viii], perhaps a result of the decreasing whale populations.
In a cruel twist of fate, Megalodon’s size may have assisted the Great Whites in outcompeting them. Being large comes with a whole host of problems, most notably that you need plenty of resources – most notably food – to survive. Without an abundance of whales, Megalodon may have been forced into smaller meals like seals and fish, common prey of Great Whites. For Megalodon, hunting quick and maneuverable prey would have been cumbersome and unrewarding.
On the other hand, the smaller and more agile Great Whites had no such problem. We’ve all seen videos of Great Whites breaching the surface in pursuit of a poor seal, a testament to their skills as hunters of agile prey. Could a Megalodon hunt in such a manner? Perhaps, though it isn’t hard to imagine its massive frame prevented it from catching quicker and more athletic prey. In the world of the Great White, Megalodon’s greatest strength may have become its greatest weakness, aiding a much more modern killer in taking over.
Theory #4: Ice Age Coming: Hide your Kids?
Besides the issue of plummeting temperatures, the Ice Ages presented a different problem for Megalodon. The formation of glaciers resulted in much of earth’s water being trapped at the poles, causing sea levels to plummet. Though this wouldn’t have affected adult Megalodon, it would have had a catastrophic effect on a much more vulnerable population: their young.
Fossil sites from coastal regions across the globe have revealed that Megalodon used nursery sites to harbour their young. In places like Panama, Spain, and the Eastern United States, fossils of Megalodon juveniles ranging from 10-meter-long sub-adults to 2-meter-long infants are found together in what were once shallow coastal regions[ix]. These sites would have offered protection for the young Meg’s while also providing a smorgasbord of smaller fishes to feed on.
Unfortunately for the baby Megalodon, the advent of large-scale glaciation doomed their shallow paradise. Baby Meg’s would have had to fend for themselves in the open oceans, where they may have been subject to predation from Great Whites, toothed whales, or worst of all: their parents. The environmental stability offered by sheltered coastal regions would have been replaced by the unpredictable currents of deeper waters. Lastly, the little Megalodon lost the easy supply of small fishes and sharks offered by the nurseries, making hunting a more difficult endeavour.
Without their nurseries, the entire Megalodon population would have become vulnerable. Another downside that comes with being large is that your species reproduces slowly, meaning that any wide-scale changes that affect your progeny can drastically affect your species viability. If Megalodon juveniles – which likely weren’t too common to begin with – were facing ecological stress, fewer individuals would survive to adulthood. Repeated over the course of generations, the once plentiful Megalodon may have soon faced extinction.
Bottom Line: Why not all these theories?
One of the greatest misconceptions about extinction is that it is caused by a singular event. The extinction of a species is the culmination of multiple factors working simultaneously over the course of thousands, if not millions, of years. It’s more than likely that some combination of factors – cooling oceans, whale extinctions, new competitors, and disappearing nurseries – worked in tandem to bring down the mighty Megalodon. With Megalodon out of the picture, predators such as Great Whites and Orcas rose to the top of the food chain, while whales grew larger than any animals that had come before.
The other added benefit is that we can go swimming in the ocean without fear of being gobbled up by Megalodon…unless you’re in a Jason Statham movie. Decent trade-off if you ask me…
Thanks for reading this article! If you’re interested in Megalodon and would like to know more, read the truth about Megalodon here at Max’s Blogosaurus!
I do not take credit for any images found in this article.
Header image courtesy of Moriarty’s Gem Art, found here
Megalodon and the Thresher Shark courtesy of Esther Van Hulsen, found here
Megalodon breach courtesy of Hugo Salais, found here
Megalodon hunt courtesy of Alberto Collareta, found here
Megalodon meeting Livyatan courtesy of Gabriel Ugueto, found here
The Great White Shark and Megalodon courtesy of Christina Spence Morgan, found here
Baby Megalodon tooth courtesy of Daniel Leifheit, found here
Livyatan snacking on a Megalodon courtesy of Rudolf Hima, found here
Beached Megalodon courtesy of Emiliano Troco, found here
[i] Shimada, Kenshu, et al. “Revisiting Body Size Trends and Nursery Areas of the Neogene Megatooth Shark, Otodus Megalodon (Lamniformes: Otodontidae), Reveals Bergmann’s Rule Possibly Enhanced Its Gigantism in Cooler Waters.” Historical Biology, 2022, pp. 1–10., https://doi.org/10.1080/08912963.2022.2032024.
[ii] Collareta, Alberto, et al. “Did the Giant Extinct Shark Carcharocles Megalodon Target Small Prey? Bite Marks on Marine Mammal Remains from the Late Miocene of Peru.” Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 469, 2017, pp. 84–91., https://doi.org/10.1016/j.palaeo.2017.01.001.
[iii] Aguilera, Orangel A., et al. “Giant-Toothed White Sharks and Cetacean Trophic Interaction from the Pliocene Caribbean Paraguaná Formation.” Paläontologische Zeitschrift, vol. 82, no. 2, 2008, pp. 204–208., https://doi.org/10.1007/bf02988410.
[iv] Kallal, R. J., et al. “Bone Reactions on a Pliocene Cetacean Rib Indicate Short-Term Survival of Predation Event.” International Journal of Osteoarchaeology, vol. 22, no. 3, 2010, pp. 253–260., https://doi.org/10.1002/oa.1199.
[v] Pimiento, Catalina, et al. “The Pliocene Marine Megafauna Extinction and Its Impact on Functional Diversity.” Nature Ecology & Evolution, vol. 1, no. 8, 2017, pp. 1100–1106., https://doi.org/10.1038/s41559-017-0223-6.
[vi] Uhen, Mark D, and Nicholas D Pyenson. “Diversity Estimates, Biases, and Historiographic Effects: Resolving Cetacean Diversity in the Tertiary.” Palaeontologia Electronica , Jan. 2007.
[vii] McCormack, Jeremy, et al. “Trophic Position of Otodus Megalodon and Great White Sharks through Time Revealed by Zinc Isotopes.” Nature Communications, vol. 13, no. 1, 2022, https://doi.org/10.1038/s41467-022-30528-9.
[viii] See Above.
[ix] Lomax, Dean R., and Bob Nicholls. Locked in Time: Animal Behavior Unearthed in 50 Extraordinary Fossils. Columbia University Press, 2021.