Megalodon, the largest shark to have ever terrorised our planet's oceans, may have gone extinct owing to its limited dietary preference for dwarf whales, according to new research.
You're going to need a bigger boat. (Illustration: Alberto Gennari/Palaeogeography, Palaeoclimatology, Palaeoecology)
The megalodon, a fearsome aquatic predator measuring 16m long and boasting 3m-wide jaws, went extinct about 2.6 million years ago after a fairly respectable 14-million-year run. The reason for its demise, say researchers from the University of Pisa in Italy, may have something to do with its preference for relatively small prey, including now-extinct dwarf whales and seals. When these prey animals disappeared, the gigantic megalodon was not able to adapt and eat from a different menu, ultimately resulting in its own extinction.
Palaeontologist Alberto Collareta, who led the study, says this cascade of despair was triggered by climate change, when the cooling of the Earth caused ice to form in glaciers and at the poles. The resulting drop in sea levels, along with the subsequent loss of coastal habitat, forced the diminutive whales into the open ocean, an environment to which they were poorly suited. At the same time, these environmental changes drove the evolution of larger whales, which were able to make long-distance seasonal migrations to feeding grounds around the poles.
With the dwarf whales gone, the megalodon was out of luck. The larger whales would have been more difficult prey to tackle, but more importantly, the giant sharks couldn't leave their preferred warm waters in pursuit of the pole-bound whales.
It's a good theory, but in addition to the climate science, Collareta's team has collected some empirical evidence. The researchers examined bite marks left on mammalian fossils found in southern Peru — bite marks that were matched to the megatoothed megalodon. The tell-tale bites were found on an extinct species of baleen whale and an early type of seal. Both of these creatures grew to less than 5m in length, about a third the length of megalodon.
The evidence is a bit circumstantial and certainly limited, but the pieces fit nicely together. More fossil evidence would help bolster the claim (for example, bite marks on bigger prey would undermine the theory, while bite marks on more fossils of smaller prey would strengthen it). To complicate matters, there are other competing theories; recent research suggests the megalodon faced competition from white sharks and orca whales.
Like so many things in science, answers aren't always clean cut.