Megalodon was a truly vicious killer, but not a cold-blooded one

The enormous megalodon was the most formidable marine predator that ever graced our oceans. It was indeed a killer, but not the cold-blooded kind.

Environmental scientists from UCLA, UC Merced, and William Paterson University have completed an exciting research analysis about the megalodon.

The study provides new insight into the warm-blooded nature of this ancient shark. The insights derived could potentially explain the reasons behind the megalodon’s extinction.

The ancient megalodon, which went extinct roughly 3.6 million years ago, once dominated the seas. The researchers analyzed isotopes in the tooth enamel of these monstrous creatures.

They concluded that megalodons maintained a body temperature of approximately 13 degrees Fahrenheit (or about 7 degrees Celsius). This was warmer than the water in which they swam.

Megalodon was a warm-blooded creature

This significant temperature difference sets the megalodon apart from other sharks that coexisted during its era. It’s enough evidence to categorize the megalodon as a warm-blooded creature. This finding was reported in their paper published in the Proceedings of the National Academy of Sciences.

The study also posits that the energy the megalodon used to maintain its warm body temperature could have contributed to its eventual extinction. This offers a valuable perspective for understanding current and future environmental shifts.

“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,” commented lead researcher Robert Eagle. He is an assistant professor of atmospheric and oceanic sciences at UCLA. He’s also a member of the UCLA Institute of the Environment and Sustainability.

Megalodon was part of a group known as mackerel sharks

Believed to have grown up to 50 feet in length, megalodons were part of a group of sharks known as mackerel sharks. This category includes modern-day creatures such as the great white and thresher sharks.

Most fish are cold-blooded, with body temperatures that match their surroundings. Mackerel sharks, however, can keep parts of their bodies warmer than the surrounding water. This unique trait is known as mesothermy and regional endothermy.

Sharks are distinct from fully warm-blooded or endothermic animals like mammals. This is because they store heat generated by their muscles. In mammals, body temperature is regulated by a part of the brain called the hypothalamus.

Evidence has suggested that the megalodon may have been mesothermic. However, until now, there was no data to support this theory.

Without evidence from soft tissues that influence body temperature in modern sharks, it has been challenging to determine if, or to what extent, the megalodon was endothermic.

Studying the megalodon’s teeth to find answers

In their pioneering study, the scientists sought answers in the most abundant fossil remains of the megalodon: its teeth. Teeth are primarily composed of a mineral called apatite.

Apatite contains atoms of carbon and oxygen. These atoms can appear in “light” or “heavy” forms, known as isotopes. The ratio of light to heavy isotopes in apatite can depend on a range of environmental factors.

“The isotopes preserved in the minerals that make up teeth can be seen as a kind of thermometer, but one whose reading can be preserved for millions of years,” explained Randy Flores, a UCLA doctoral student who worked on the study.

“Because teeth form in the tissue of an animal when it’s alive, we can measure the isotopic composition of fossil teeth to estimate the temperature at which they formed. That gives us the approximate body temperature of the animal in life.”

Most ancient and modern sharks cannot maintain body temperatures significantly higher than the surrounding seawater. Thus, the isotopes in their teeth reflect temperatures close to that of the ocean.

However, in warm-blooded animals, the isotopes in their teeth document the effect of body heat. This gives an indication of temperatures warmer than the surrounding water.

The researchers hypothesized that any difference between the isotope values of the megalodon and those of other sharks from the same period would reveal the megalodon’s ability to warm its body.

They collected teeth from megalodon and other contemporary sharks from five global locations. The research team then analyzed them using mass spectrometers.

They found that megalodons’ teeth consistently yielded average temperatures. This indicated an impressive ability to regulate body temperature.

Being warm-blooded probably resulted in megalodon’s extinction

This warm body temperature allowed the megalodon to move faster. It could also survive in colder waters and spread around the world. Ironically, this evolutionary advantage may have contributed to the species’ downfall.

The megalodon thrived during the Pliocene Epoch, from 5.33 million years ago until 2.58 million years ago. Global cooling during this period triggered sea level changes and ecological shifts that the megalodon could not survive.

“Maintaining an energy level that would allow for the megalodon’s elevated body temperature would require a voracious appetite. This appetite may not have been sustainable in a time of changing marine ecosystem balances when it may have even had to compete against newcomers like the great white shark,” Flores said.

Looking to the future, project co-leader Aradhna Tripati, a UCLA professor of Earth, planetary, and space sciences, mentioned that the team plans to use the same methodology to study other species.

“Having established endothermy in the megalodon, the question arises of how frequently it is found in apex marine predators throughout geologic history,” she added.

More about megalodon

The megalodon, whose name translates from Greek to “big tooth,” is one of the most famous extinct species of shark, known for its enormous size and powerful build. Here’s everything we knew about the megalodon:

Size and Appearance

The megalodon is considered one of the largest predatory marine animals in the history of our planet. Although the exact size is debated, most scientists agree that megalodons likely reached lengths of 50 to 60 feet.

As for its appearance, due to the lack of a complete megalodon skeleton (shark skeletons, made of cartilage, do not fossilize well), much of what we know comes from the size and structure of the remaining teeth and vertebrae.

Scientists also use comparisons with contemporary sharks. It likely resembled a significantly larger, bulkier version of today’s great white shark.

Diet and Hunting Style

The megalodon was a top-level predator and could take down large marine mammals like whales and seals. The megalodon’s powerful jaws, lined with serrated, heart-shaped teeth, could exert an incredible bite force. It was perhaps one of the strongest among all known animals.

The exact hunting strategies are not known. They may have involved attacking the soft underbelly or fins of their prey to immobilize them. This is a similar strategy to that of modern great white sharks.

Habitat and Range

Megalodon fossils have been found all over the world. This suggests that these giant sharks were cosmopolitan. They lived in a variety of marine environments, from shallow coastal waters to deeper oceans. They were likely more prevalent in warmer waters.

Reproduction

Little is known about megalodon’s reproductive habits. It is possible they gave live birth like modern sharks. It’s also likely that, similar to some shark species today, they practiced intrauterine cannibalism. This is where the larger, stronger pups consume their siblings in the womb.

Extinction

The megalodon went extinct around 3.6 million years ago. This was likely due to a combination of climate change, a decline in their food supply, and competition with other apex predators like the great white shark.

As the Earth entered an ice age, the seas cooled and sea levels dropped. This may have impacted the megalodon’s preferred warm, coastal habitats. It would have also reduced the populations of the marine mammals they hunted.

Legacy and Influence

Today, the megalodon continues to capture public interest. It has made appearances in pop culture, movies, and video games, often portrayed (somewhat inaccuratively) as a monster of the deep.

Scientifically, studying megalodon and its ecology can provide important insights into marine ecosystems’ past and present dynamics.