Megalodon sharks may have been forced into extinction by great whites

By Corryn Wetzel

The extinction of the world's biggest shark, megalodon, may have been accelerated by great whites competing for the same prey. An analysis of zinc in ancient tooth enamel of both types of shark gives a new insight.

It has been 3.5 million years since the last megalodon died, but the reason for his demise remains a mystery. Kenshu Shimada and his colleagues were eager to find out more about the giant fish's place in the food chain, after previous research suggested that it may have been difficult to find enough food to meet their huge appetite.

The bones of Megalodon's body are made of a type of cartilage that doesn't fossilise well, so researchers are left with the animals' palm-sized teeth.

We wanted to see if we could decipher the diet of extinct sharks, including the prehistoric great white shark, using zinc isotopes preserved in fossilised teeth.

Read more: Largest ever shark was doomed by its taste for dwarf whales

This is the first time scientists have used zinc isotope analysis on shark teeth, but the technique has been found to be a powerful tool to decipher the relative positions in the food chain among diverse species.

The team used a dental drill to sample 20 living shark species and 13 extinct shark species. The zinc levels in the individual teeth were compared. The balance of zinc in the diet and the type of food an animal has eaten is indicative of the zinc needed for animal life.

The researchers found that the zinc ratio in the sample was very similar to that of the ancient great white sharks. When the two species co-existed, they probably shared a similar apex predator position because both had low levels of zinc in their teeth.

Evidence of fossilised bite marks suggests that great whites and megalodon shared a diet of small whales, seals and sea lions. Competition for food with great whites may have been a factor in the extinction of the megalodon.

Nature Communications is a journal.

Wild Wild Life is a monthly newsletter that celebrates the diversity and science of animals, plants and Earth.