Megalodon: Largest Ever Shark's Diet Surprises Geoscientists
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A new study has uncovered surprising insights into the feeding habits of the largest predatory fish to ever roam the Earth's oceans, challenging long-standing assumptions about the prehistoric predator.
For centuries, scientists believed that Otodus megalodon hunted exclusively at the top off the food chain, but a new study led by Jeremy McCormack from the Department of Geosciences at Goethe University Frankfurt found that its diet was far more flexible than previously thought.
Longer than a truck with a trailer (reaching up to almost 79 feet long) and weighting almost twice as much, Megalodon, ruled the oceans between 20–3 million years ago, frequently on the hunt for prey to satisfy its astonishing 100,000 kilocalories-per-day nutritional demand.
Its massive jaws were filled with triangular teeth, each the size of a hand, and its deadly bite had the force of an industrial hydraulic press, leaving no hope for any creature crossing its path.
It was thanks to its fossilized teeth that McCormack, in collaboration with other scientists from Germany, France, Austria and the US, were able to discover the apex predator's unusual dietary habits.
A stock image shows a 3D illustration of the Otodus Megalodon, the largest predatory fish that has ever existed.
A stock image shows a 3D illustration of the Otodus Megalodon, the largest predatory fish that has ever existed.
getty images
By analyzing the levels of zinc in the fossils, the study found that while Megalodon did surely feast on whales and dolphins whenever it had a chance, the shark adjusted its diet based on availability of the prey.
Zinc occurs in atomic variants (isotopes) of different weights, and is ingested with food. Less of the heavier isotope zinc-66 than the lighter isotope zinc-64 is stored in muscles and organs. Predatory fish absorb significantly less zinc-66 and those at the top of the food chain absorb even less.
"Since we don't know how the ratio of the two zinc isotopes at the bottom of the food pyramid was at that time, we compared the teeth of various prehistoric and extant shark species with each other and with other animal species. This enabled us to gain an impression of predator–prey relationships 18 million years ago," explained McCormack in a statement.
Sea bream—a fish which fed on mussels, snails and crustaceans—formed the lowest level of the food chain, followed by smaller shark species such as requiem sharks and the ancestors of today's cetaceans, dolphins and whales.
Larger sharks such as sand tiger sharks were further up the food pyramid, and at the top were giant sharks like Araloselachus cuspidatus and the Otodus shark genus, which includes Megalodon.
Results of the study showed that the levels of zinc found in the Megalodon couldn't be sharply differentiated from the lower levels of the pyramid, suggesting that the largest shark that ever lived was flexible enough to feed on both marine mammals and large fish from the top of the food pyramid as well as lower levels.
Jeremy McCormack at the mass spectrometer, which is used to determine the zinc isotope ratio. This ratio provides information about the diet of Otodus megalodon. Photo: Uwe Dettmar for Goethe University
Jeremy McCormack at the mass spectrometer, which is used to determine the zinc isotope ratio. This ratio provides information about the diet of Otodus megalodon. Photo: Uwe Dettmar for Goethe University
Uwe Dettmar, Goethe University
"Our study tends rather to draw a picture of megalodon as an ecologically versatile generalist," McCormack added.
The shark's diet also greatly varied depending on its location and regional availability of prey. The teeth used for the study mostly came from 18-million-year-old fossil deposits in the German cities of Sigmaringen and Passau—and sharks in these locations showed different food habits.
The creatures from Passau fed more on prey from lower levels of the food pyramid, probably due to lack of bigger fish in the area.
McCormack said that the new method of determining tooth zinc isotope ratios has once proven to be a valuable instrument for paleoecological reconstructions.
Kenshu Shimada, paleobiologist at DePaul University in Chicago, USA, and coauthor of the study added: "It gives us important insights into how the marine communities have changed over geologic time, but more importantly the fact that even 'supercarnivores' are not immune to extinction."
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