An article published in the journal “Scientific Reports” describes an analysis of fossil teeth of great white shark (Carcharodon carcharias) discovered in various locations, including what used to be a nursery in today’s Chile where there were mostly very young individuals. A team of researchers led by Jaime A. Villafaña of the Institute of Paleontology of the Austrian University of Vienna analyzed the fossils of individuals of various ages including the ones discovered in Peru and another location in Chile concluding that great white sharks used some areas as nurseries for millions of years. This behavior stresses the importance of certain habitats for the survival of a species known among today’s top predators and yet considered endangered, above all because of humans.
The great white shark (bottom photo ©Terry Goss), also called simply the great white or of the white shark, is the largest predator among fish and one of the largest fish existing today. The oldest fossil remains of this species date back to about 16 million years ago, in the Mid-Miocene period, but reconstructing its history and its evolutionary tree is problematic. Sharks’ cartilaginous skeletons don’t fossilize, so only ancient sharks’ teeth got preserved until today. The consequence is that the relationships with extinct species are theorized based on the characteristics of those teeth, but are often the subject of discussions. In great white shark’s case, the similarity with the teeth of the extinct species Carcharodon megalodon led many scientists to believe that the two species are closely related, but others believe that the extinct species Carcharodon hubbelli was closer to the great white shark. In essence, these fish’s family tree is still very doubtful.
Young great white sharks are born in specific areas where they’re protected from other predators until they’re large enough not to fear them anymore. These nurseries are crucial for the stability of the great white shark population and contributed to this species’ success. For this reason, in recent years research in those areas tried, also to remedy the decline of a species that is among the most important top predators in the world but is failing to keep up with human activities.
Jaime A. Villafaña and his colleagues analyzed fossil teeth of great white sharks that are between 2 and 5 million years old discovered in various areas near the Pacific Ocean coast to try to reconstruct part of this species’ history. In the localities of Pisco, Peru, and Caldera, Chile, the fossil teeth were mainly of adult individuals and this suggests that those were feeding grounds. Instead, in the locality of Coquimbo, Chile, the prevalence was of very young individuals, and that indicated that it was a nursery.
The top image (Courtesy Jaime Villafaña/Jürgen Kriwet) shows a representation of the mouth of a great white shark (A) with the indication of the various teeth and a series of examples of fossil teeth (B) for each position.
The discovery of a paleo-nursery is of great importance in the reconstruction of the great white shark’s history. It dates back to an era when the climate was much warmer than today with conditions that could be those of a not too distant future due to climate change. Studying a past that can even be remote to try to predict the future is a strategy that can include paleontologists as well. Paleobiologist Jürgen Kriwet, also from the Institute of Paleontology of the University of Vienna and among the authors of the research, stated that the results indicate that rising sea temperatures will change the distribution of fish in temperate areas and move these important breeding areas.
The analysis of the data collected suggests that in the time between the most and least ancient teeth found, between 2 and 5 million years ago, the population of great white sharks in the South American Pacific area was stable. This confirms other paleontological and paleoenvironmental evidence discovered in the past. It’s a difficult fish to study, so every discovery is useful to try to understand its reproductive habits, also in the hope to avoid causing its extinction.
