The largest marine predator that ever lived was no cold-blooded killer. A new analysis by ecologists at UCLA, UC Merced and William Paterson University sheds light on the warm blooded animal’s ability to regulate its body temperature and may help explain why it went extinct.
After analyzing isotopes in the tooth enamel of an ancient shark that went extinct about 3.6 million years ago, scientists concluded that the megalodon could maintain a body temperature that was about 13°F (about 7°C) higher than the surrounding water.
This temperature difference is greater than the temperature difference that has been determined for other sharks that lived alongside the megalodon, and is large enough to classify megalodons as warm-blooded.
A paper published in the journal Proceedings of the National Academy of Sciences suggests that the amount of energy the megalodon used to keep warm contributed to its extinction. And this has implications for understanding current and future environmental changes.
“Studying the driving factors behind the extinction of a highly successful predatory shark like the megalodon can provide insight into the vulnerability of large marine predators in modern ocean ecosystems experiencing the effects of ongoing climate change,” said lead researcher Robert Eagle, UCLA assistant professor. in atmospheric and oceanic sciences and a member of the UCLA Institute of the Environment and Sustainability.
Megalodons, which are thought to have reached lengths of up to 50 feet, belonged to a group of sharks called mackerel sharks – members of this group today include the white shark and thresher shark. While most fish are cold-blooded with body temperatures that are the same as the surrounding water, mackerel sharks maintain all or parts of their body temperatures somewhat warmer than the water around them, traits called mesothermy and regional endothermy.
Sharks store the heat generated by their muscles, distinguishing them from fully warm-blooded or endothermic animals such as mammals. In mammals, an area of ​​the brain called the hypothalamus regulates body temperature.
Various lines of evidence have suggested that Megalodon may have been mesothermic. But without data from the soft tissues that control body temperature in modern sharks, it was difficult to determine whether or to what extent Megalodon was endothermic.
The researchers collected teeth from megalodon and other shark contemporaries from five locations around the world and analyzed them using mass spectrometers at UCLA and UC Merced. Using statistical modeling to estimate seawater temperatures at each location where the teeth were collected, the researchers found that megalodon teeth consistently exhibited average temperatures that suggested they had an impressive ability to regulate body temperature.
Its warmer body allowed the megalodon to move faster, tolerate colder water, and spread across the globe. But it was this evolutionary advantage that may have contributed to its downfall, the researchers wrote.
Megalodon lived during the Pliocene Epoch, which began 5.33 million years ago and ended 2.58 million years ago, and global cooling during this period caused sea level changes and ecological changes that Megalodon did not survive.
“Maintaining an energy level that would allow megalodon’s elevated body temperature would have required a voracious appetite that may not have been sustainable during a time of changing marine ecosystem balance, when it may have even had to compete with newcomers such as the great white shark,” Flores said.
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