Megalodon is the largest known shark to have ever lived. Karen Carr/Wikimedia Commons CC BY 3.0
Josh Davis 03 Dec 2015, 16:14

When it was alive and cruising the world’s oceans, megalodon dominated the environment as one of the most indomitable predators that has ever existed. Chasing down any marine mammal to cross its path – from seals to sperm whales – the massive shark had little to worry about at the top of the food chain, except maybe other members of its own species. New research has looked into this giant predator’s behavior, and calculated how fast the animals could have swam.

After looking at how the speed of modern day sharks is linked to predator-prey dynamics, as well as the physiology of the animals, the researchers extrapolated their results to include megalodon: the largest known shark ever to have existed. Using these calculations, they found that a megalodon measuring 20 meters (65 feet) long and weighing 48 tonnes (53 tons) probably swam at an astonishing 5 meters (16.5 feet) per second, twice that of the largest living shark, the great white.    

 

The raltive sizes and speed at which the sharks looked at in the study can swim. Institute of Zoology/Zoological Scoiety of London

“The megalodon was an enormous apex predator that appeared to cruise the oceans at speeds unrivalled by any shark species present today,” explained Dr. David Jacoby, from the Zoological Society of London, who led the study published in Biology Letters. “The mathematical model not only allows us to estimate the speed of this super-predator, but also helps us to predict the movement characteristics of other elusive marine sharks, such as many deep-sea species.”

While looking into the relationship between swimming speeds of sharks and their metabolism, they developed a model from 64 studies on 26 species that showed they could predict how fast species were able to move, just by looking at how big the animals were. As sharks increase in size their metabolism also increases in scale, so the bigger the animal, the larger the metabolism. In order to maintain a sufficient flow of water over the sharks gills to get enough oxygen to uphold this metabolism, the shark must swim at a certain minimum speed.

They found that this relationship, between size and speed, formed a “positive scaling relationship,” and was reliable enough to allow for accurate prediction. The researchers then created a model from this relationship, which was shown to closely match the data collected from tracked sharks in the wild. This allowed the researchers to then use the calculations to infer the speed of particular species which are elusive, or in the case of the megalodon, extinct. 

The scientists think that these figures give a good indication of the minimum speed at which sharks can swim, but highlight that more research is needed into how other variables, such as water temperature and habitat type, might also influence how fast the animals can move. Even so, the relationship they have identified is still able to hold over five separate groups of shark, and could be invaluable in helping to determine the behavior and ecology of other little-studied species. 

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