Researchers from the US, Switzerland, Italy, and Peru found evidence suggesting that the ancestors of modern sperm whales became the fat source of ancient sharks. Their study described fossil bones from the late Miocene era found in Peru.
Sperm whales are the largest toothed predator and the most distributed mammal around the world. They have fatty nasal organs to produce sounds and sonar signals for echolocation. However, due to the said feature, they became a prime target of ancient sharks around 5 to 6 million years ago.
Bark Marks on Sperm Whale Fossils
In the study titled "Sperm Whales (Physeteroidea) From the Pisco Formation, Peru, and Their Trophic Role as Fat Sources for Late Miocene Sharks," published in the journal Proceedings of the Royal Society B, researchers reported that they found bite marks on several sperm whale skulls from the Miocene era found in Pisco formation in Peru.
The researchers focused their study on the bite marks on the upper parts of the fossilized physeteroid skulls that house the nasal passages, according to Phys.org. Although modern sperm whales have enlarged nasal organs that they use for sound production, it is also chock full of fat that sharks love.
Analysis showed that the marks were caused by sharks in progressive attacks, wherein large sharks attack first, followed by waves of smaller sharks. A separate study also confirms that megalodon sharks target the heads of ancient sperm whales
More so, their analysis reveals that sharks focused mainly on the part of the head housing the nasal organs, indicating that they were going for the fat surrounding them. Fats are essential nutrients for sharks and sperm whale noses are perfect for their high-energy meal.
Ancient and Modern Sharks Prefer Eating High Fat Diet
The team noted that physeteroids were a diverse group of whales that lived during the Miocene era, but all had overly large heads with nasal organs that helped them communicate with one another over long distances. Similar bites were found on physeteroids from different sites around the globe, suggesting that sharks actively sought them out as their source of fat.
Study lead author Aldo Benites-Palomino, a Ph.D. candidate at the University of Zurich, told Newsweek that the noses of modern sperm whales contain one of the highest concentrations of fats and oils of any animal.
He added that since baleen whales in the Miocene era were slender and smaller, they did not have high-fat content similar to ancient sperm whales, hyperdiverse groups, and are an ideal food source for sharks.
Even in modern seas, sharks are observed to prefer eating areas with high-fat content, such as the blubber on the bellies of dead whales. The study indicates sharks' preference for fat had lasted for millions of years and that they were able to figure out which part of sperm whales had the most fat.
Lastly, researchers noted that their findings showed that all attacks were post-mortem events - meaning they happened when whale carcasses were floating for days until all fat was ingested by sharks.
RELATED ARTICLE : Evidence of Megatoothed Shark Attack on Whale 15 Million Years Ago Preserved in Ancient Tooth
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