A new analysis by environmental scientists from UCLA, UC Merced, and William Paterson University reveals that the ancient shark species known as megalodon had the ability to regulate its body temperature, making it warm-blooded. The study suggests that the energy required to maintain a warmer body temperature may have contributed to the extinction of megalodon, and the findings have implications for understanding the vulnerability of large marine predators in the face of climate change.
Researchers from UCLA, UC Merced, and William Paterson University conducted an analysis of the megalodon, the largest marine predator that ever existed, to understand its ability to regulate body temperature and the factors that led to its extinction.
Using isotopic analysis of tooth enamel from the ancient shark, the scientists determined that megalodon could maintain a body temperature approximately 13 degrees Fahrenheit (7 degrees Celsius) warmer than the surrounding water. This temperature difference was greater than that observed in other sharks that coexisted with megalodon and was significant enough to classify megalodons as warm-blooded.
The study, published in the Proceedings of the National Academy of Sciences, suggests that the energy expenditure required to maintain a warm body temperature may have contributed to the extinction of megalodon. The findings also have implications for understanding the vulnerability of large marine predators in present and future ocean ecosystems affected by climate change.
Lead researcher Robert Eagle, an assistant professor of atmospheric and oceanic sciences at UCLA, explains, “Studying the driving factors behind the extinction of a highly successful predatory shark like megalodon can provide insight into the vulnerability of large marine predators in modern ocean ecosystems experiencing the effects of ongoing climate change.”
Megalodons, believed to have reached lengths of up to 50 feet, belonged to a group of sharks called mackerel sharks, which includes the great white and thresher shark. Unlike most fish that are cold-blooded, mackerel sharks exhibit qualities called mesothermy and regional endothermy, where they keep parts of their bodies warmer than the surrounding water.
To study the warm-blooded characteristics of megalodon, the researchers focused on analyzing isotopes in the shark’s teeth. Teeth contain a mineral called apatite that contains carbon and oxygen atoms, and the composition of these isotopes can provide insights into an animal’s living environment, diet, and body temperature. The isotopic composition of fossil teeth acts as a “thermometer” preserved for millions of years.
The researchers collected teeth from megalodon and other shark species that coexisted during the same period from various locations worldwide. By analyzing the isotopes using mass spectrometers, the scientists estimated the sea water temperatures at the sites where the teeth were found. The analysis consistently showed that megalodon had the ability to regulate its body temperature.
While the warmer body temperature of megalodon allowed for advantages such as increased speed and tolerance to colder waters, it may have contributed to its downfall. The megalodon existed during the Pliocene Epoch, which experienced global cooling that led to sea level and ecological changes that the species could not adapt to.
The researchers suggest that maintaining the energy level required for megalodon’s elevated body temperature would have demanded a high appetite that might not have been sustainable during a period of changing marine ecosystems. This included potential competition with newcomers like the great white shark.
Moving forward, the researchers plan to investigate the prevalence of endothermy, or warm-bloodedness, in other apex marine predators throughout geologic history.