Analysis of fossil teeth upends what’s known about megalodon’s diet, scientists say

What scientists understand about the voracious feeding habits of the colossal megalodon could be up for some revision. The prehistoric predator that went extinct about 3.6 million years ago was not hunting only large marine mammals such as whales as researchers widely thought, a new study has found. Instead, minerals in fossilized teeth reveal that megalodon might have been an opportunistic feeder to meet its remarkable 100,000-calorie-per-day requirement. “When available, it would probably have fed on large prey items, but when not available, it was flexible enough to feed also on smaller animals to fulfill its dietary requirements,” said lead study author Jeremy McCormack, a geoscientist at Goethe University in Frankfurt, Germany. The study, published Monday in the journal Earth and Planetary Science Letters, also showed there were regional differences in the giant shark’s feeding habits. The finding suggests megalodon would pursue whatever was in local waters, devouring other top predators and smaller prey alike. “They were not concentrating on certain prey types, but they must have fed throughout the food web, on many different species,” McCormack said. While certainly this was a fierce apex predator, and no one else would probably prey on an adult megalodon, it’s clear that they themselves could potentially feed on almost everything else that swam around.” Megalodon dispatched its prey with a ferocious bite and lethal, serrated teeth that could reach up to 7 inches (18 centimeters) long — the size of a human hand. The superpredator’s teeth — abundant in the fossil record — are what McCormack and his colleagues used to conduct a geochemical analysis, unlocking fresh clues that could challenge megalodon’s role as sole king of the ancient seas. Zinc in megalodon teeth It’s not the first time that a study has challenged previous knowledge about the enormous sea creature. In fact, many questions remain unanswered about Otodus megalodon — its scientific species name meaning “giant tooth” — since no complete fossil has ever been discovered. The lack of hard evidence stems from the fact that fish skeletons are made of softer cartilage rather than bone, so they don’t fossilize very well. Recent research found that the animal was more warm-blooded than other sharks, for example, and there is an ongoing debate about its size and shape. Scientists who created a 3D reconstruction suggested in 2022 that megalodon was about three times as long as a great white shark — about 52 feet (16 meters). However, a March study hypothesized that the megashark was actually much larger — up to 80 feet (24 meters) in length and even longer than the fictional version in the 2018 blockbuster “The Meg,” which suggested the ancient predator was 75 feet (23 meters) from head to tail. As for megalodon’s feeding habits, determining what it ate based on fossil evidence poses challenges, according to McCormack. “We know that they fed on large marine mammals from tooth bite marks,” he said. “Of course, you can see bite marks on the bones of marine mammals, but you will not see them if they fed on other sharks, because sharks don’t have bones. So there’s already a bias in this kind of fossil record.” To glean more about megalodon’s prey selection, McCormack and his coauthors looked at the giant shark’s fossilized teeth and compared them with those of other animals that lived at the same time, as well as teeth from modern sharks and other predators such as dolphins. The researchers used specimens from museum collections and samples from beached animal carcasses. Specifically, the study team conducted a lab analysis of zinc, a mineral that is acquired only through food. Zinc is essential for living organisms and plays a crucial role in tooth development. The ratio of heavy and light zinc isotopes in the sharks’ tooth enamel preserves a record of the kind of animal matter that they ate. Different types, or isotopes, of zinc are absorbed when fish and other animals eat, but one of them — zinc-66 — is stored in tooth enamel much less than another, zinc-64. The ratio between those zinc isotopes widens the further away an animal gets from the lowest level of the food chain. That means that a fish eating other fish would have lower levels of zinc-66 compared with zinc-64, and the fish that eat those fish will have even less zinc-66 compared with zinc-64, creating ratio markers that can help draw up a sequence of the food chain. The researchers found that sea bream, a fish that feeds on mussels and crustaceans, was at the bottom of their reconstructed chain, followed by smaller sharks from the Carcharhinus genus, up to 9.8 feet (3 meters) in length, and extinct toothed whales comparable in size to modern dolphins. Farther up were larger sharks such as the Galeocerdo aduncus, similar to a modern tiger shark, and occupying the top slot was megalodon — but its zinc ratios were not so different as to suggest a massive gap with the lower-tier animals, meaning they might have been part of megalodon’s diet, too. “Based on our new results, we see that it was clear it could feed at the very top, but it was flexible enough to feed also on lower (levels of the food chain),” McCormack said. In addition, the researchers found megalodon was not alone at the top of the food chain but instead shared the spot with other “opportunistic supercarnivores” such as its close relative Otodus chubutensis and the lesser-known Araloselachus cuspidatus, another giant fish-eating shark. That revelation challenges the assumption that megalodon was the exclusive ruler of the oceans and draws comparisons with the great white shark, another large opportunistic feeder. The finding also reinforces the idea that the rise of the great white may have been a factor in megalodon’s extinction, according to paleobiologist Kenshu Shimada, one of the coauthors of the latest study. “One of the contributing factors for the demise of megalodon has been hypothesized to be the rise of the great white shark, which feeds on fish when young and shifts its diet to marine mammals as it becomes larger,” said Shimada, a professor of biological and environmental sciences at DePaul University in Chicago. “Our new study, that demonstrates the ‘diet overlap’ between the great white shark and megalodon, strengthens the idea that the evolution of the smaller, likely more agile and maneuverable great white shark could have indeed (driven) megalodon to extinction.” Megalodon vs. great white shark The new research allows scientists to recreate a snapshot of the marine food web that existed about 20 million years ago, according to Jack Cooper, a UK-based paleobiologist and megalodon expert who wasn’t involved with the study. “The general picture of megalodon has been of a gigantic shark munching on whales,” Cooper said in an email. “This study adds a new dimension that megalodon probably had a wide range of prey — essentially, it probably ate not just whales but whatever it wanted.” Another interesting find, he added, is that megalodon’s diet probably varied slightly between different populations, something observed in today’s great white sharks. “This makes sense and is something we would have probably expected since megalodon lived all over the world and not all of its prey items would have done; but it’s wonderful to have concrete data supporting this hypothesis,” Cooper said. The study adds to a growing body of evidence that is reshaping commonly held beliefs about megalodon and its close relatives, said Alberto Collareta, a researcher in the department of Earth sciences at Italy’s University of Pisa who was not involved in the research. “These have led us to abandon traditional reconstruction of the megatooth sharks as ‘inflated’ versions of the modern white shark. We now know that the Megalodon was something else — in terms of size, shape and ancestry, and of biology, too,” Collareta said via email. “The Miocene (palaeo)ecosystems in question did not work in a radically different way compared to their modern counterparts — even if they feature … completely extinct protagonists such as the megatooth sharks,” he added, highlighting what he found to be the report’s key takeaway. “That said, it is still useful to acknowledge that our understanding of the Meg is essentially limited to its ubiquitous teeth, a few vertebrae and a handful of scales. What I’d really love to see emerging from ‘the foggy ruins of time’ is a complete Meg skeleton… Let’s hope that the fossil record will amaze us once again.”