Why did crocodiles survive the asteroid that wiped out dinosaurs?
Around 66 million years ago, an asteroid impact caused a global catastrophe, leading to the disappearance of many animal groups, including dinosaurs. However, crocodiles and some of their relatives managed to survive. Now, scientists have discovered what might have helped them.
Ancient crocodilians (left) and dinosaurs that lived in the territory of modern Egypt about 100 million years ago. Reconstruction: Andrew McAfee / Carnegie Museum of Natural History / Wikimedia Commons
Today's crocodiles are quite similar to each other in appearance, but their ancient relatives were much more diverse. Among them were armored herbivores, bipedal predators, and giants the size of a bus.
Around 66 million years ago, an asteroid impact released a huge amount of dust and ash into the atmosphere, blocking out sunlight. The planet began to cool, food chains were disrupted, and many animal species disappeared forever. All dinosaurs also went extinct, except for birds, which also belong to this group of animals.
The catastrophe severely affected crocodilians as well, but some of their representatives managed to survive.
As reported by Scinexx.de, researchers from University College London, led by paleontologist Alfio Alessandro Chiarenza, analyzed more than seven thousand fossils and findings related to over 400 modern and extinct crocodilian species. They correlated this data with reconstructions of Earth's climate and geography over the past 245 million years.
What ancient fossils revealed
The analysis revealed an interesting pattern: despite significant differences between species, their dependence on climate remained surprisingly stable. Instead of adapting to increasingly colder conditions, crocodilians primarily moved with warm climatic zones. When the planet warmed, they spread further from the equator, and when it cooled, they returned to warmer latitudes.
For example, about 50 million years ago, the average temperature on Earth was approximately ten degrees Celsius higher than today, and polar regions were not covered in ice. Fossils indicate that crocodile relatives even lived in Antarctica.
How this helped them survive the catastrophe
Scientists decided to examine what happened to the territories suitable for crocodilians after the asteroid impact. For this, they used climate models that accounted for the reduction in solar radiation due to dust and ash in the atmosphere.
It turned out that with a 5-10% reduction in sunlight, areas near the equator and in the subtropics remained sufficiently warm. Only with a 15% decrease in solar radiation did these habitable territories disappear in computer models. However, researchers consider such an extreme scenario unlikely in reality.
Scientists suggest that a preference for a warm climate might have led some groups of crocodilians to regions where the consequences of the catastrophe were less severe. A portion of these populations could have survived there and gradually recovered their numbers.
However, this is not the only possible explanation. Other characteristics of these animals could also have influenced their survival: the ability to live both in water and on land, a diverse diet, the relatively small size of some species, and a low energy requirement.
Furthermore, conclusions about the territories that could have served as refuges are based on computer modeling, not on direct data about conditions in these regions after the catastrophe.
However, as the study authors note, today it will be harder for crocodiles to employ the strategy that helped them survive for millions of years. Previously, they could escape climate changes by moving to more favorable regions. Now, cities, roads, and agricultural lands increasingly limit this possibility. In the face of global warming, this could become a serious problem for modern species.