For millions of years, giant sharks called megalodons were the ocean’s top predators. Then along came great white sharks. New analyses of shark teeth hint that these two marine monsters hunted the same prey. That competition, it now appears, may have helped push megalodons toward extinction.
Researchers shared their findings May 31 in Nature Communications. The team was led by Jeremy McCormack. He’s a geoscientist at the Max Planck Institute for Evolutionary Anthropology. It’s in Leipzig, Germany.
Megalodon (Otodus megalodon) was one of the largest carnivores to ever live. Some grew at least 14 meters (46 feet) long. This giant began menacing the oceans around 23 million years ago. When — and why — it went extinct hasn’t been clear. The species may have died out about 2.6 million years ago. Or it may have vanished as early as 3.5 million years ago. That’s about when great white sharks (Carcharodon carcharias) emerged.
To figure out if the two sharks dined on similar food, the researchers looked at the zinc in their teeth. Zinc has two main forms, or isotopes. One is zinc-66. The other is zinc-64. The share of each isotope in tooth enamel can offer clues about where an animal fell within a food web. Plants — and plant eaters — have a lot of zinc-66, compared with zinc-64. Being higher up the food web, animals have relatively more zinc-64.
The new analyses reveal that where megalodons and great whites overlapped, their teeth had similar zinc contents. That finding suggests that their diets overlapped too. They both devoured marine mammals, such as whales and seals.
Still, just because they ate similar prey doesn’t prove these sharks fought over food, the researchers say. There are many possible reasons why megalodons went extinct. Those include changes to ocean currents over time and a big drop in the populations of marine mammals. So, even if great whites didn’t benefit megalodons, they are likely not the sole reason behind their disappearance either.
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