Climate change and human activity play major roles in the survival of crocodylian species, study proved.
Crocodylian species can be traced back 85 million years ago, in the late cretaceous period. Their extinct relatives date back 250 million years and paint the distinct evolutionary tale of how the species survived. Crocodylians have been around since the time of the dinosaurs. Often called 'living fossils', crocodylians species still live and survive in present-day Earth despite its declining numbers. Present-day crocodylians include alligators, crocodiles, gavials, and caimans.
A joint research from researchers in University of Birmingham, University of Oxford, Imperial College London and the Smithsonian Institution studied the link between extinct crocodylian species and the planet's prehistoric climate change. The study was published in the journal Nature Communications.
A massive data collection of crocodylian fossils were analyzed in direct proportion to the Earth's change in climate since the dinosaur age. Crocodylians are ectotherms. These animals are dependent on external heat for their survival. Researchers found that the steady decline of temperatures in higher latitudes contributed to the steady decline of crocodylians, many of which migrate to warmer climates. Rising temperatures, on the other hand, also affect these animals. Continents found in lower latitudes have areas that are becoming increasingly barren for the crocodylians to thrive.
"Millions of years ago these creatures and their now extinct relatives thrived in a range of environments that ranged from the tropics, to northern latitudes and even deep in the ocean", said Philip Mannion, one of the study's lead authors. "However, all this changed because of changes in the climate, and crocodylians retreated to the warmer parts of the world."
The formation of Andes Mountains in South America is one of the best examples to prove such theory. The rise of the mountains replaced the wetlands where crocodylians lived roughly five million years ago. It's not only the land-based crocodylians that are in trouble. The diversity of its cousins in the sea also suffered major loss.
Since ancient times, marine crocodylians have evolved to survive in the waters. For instance, the now extinct thalattosuchians had shark-like tails and fins that helped them roam the sea. Fluctuating sea levels played a major role in the extinction of several crocodylian groups in the waters. The decreasing size of the continental shelf made it harder for the animals and their prey to flourish.
The Cretaceous-Paleogene mass extinction that happened around 66 million years ago helped crocodylians to diversify and survive. The extinction of other creatures paved the way for the Cenozoic era, commonly known as the Age of Mammals, where we are in living in today.
The researchers believe that the warming planet may help nearly extinct crocodylian species to diversify and save its lineage. Unfortunately, the human destruction of its natural habitat continue to pose an even bigger threat.