Researchers calculate how many T. rex roamed the Earth

How many T. rex roamed the Earth? 0:46

(CNN) – Billions of Tyrannosaurus rex, also known as T. rex, roamed North America during its fascinating reign as great predators, according to a team of researchers who dedicated themselves to the arduous task of doing the math.

Paleontologists from the University of California, Berkeley, set out to determine the number of T. rex that lived during the Cretaceous period, that is, from about 65 to 98 million years ago. And they knew it would not be an easy task.

The clues of the fossils

Fossils have long been used to deepen what we know about extinct creatures like dinosaurs. But, experts say it can be challenging to use these remains to calculate population density and abundance.

“There’s just no information to make a calculation,” explained Charles Marshall, director of the Museum of Paleontology at the University of California. Marshall was part of the investigation team. «If you find an Easter egg in your garden, how can you calculate how many Easter eggs have existed? It simply cannot be done. Information is needed from another party. For example, the density of Easter eggs, where they can be found and for how many years Easter eggs have been laid in gardens.

‘Previously, researchers tried to estimate things like the possible size of the tyrannosaurus range. Also your basic energy needs. So this is a nice extension of the previous work. And it includes a lot of up-to-date information on the tyrannosaurus, ”said Nizar Ibrahim, a paleontologist at the University of Portsmouth (UK) and National Geographic explorer, who was not involved in the research.

“We just have to keep in mind that all these intriguing studies come with a certain amount of uncertainty. There is a lot we still don’t know about dinosaurs, including a Hollywood star like T. rex, ”Ibrahim added in an email.

North America had 20,000 T. rex at one time

Through studying the fossil record, density data, and data from climate models, the team at the University of California at Berkeley estimated that there were probably about 20,000 adult T. rex, which lived throughout North America and existed at any one time. This, the researchers explained in a study published in the journal Science, means that some 2.5 billion predators lived and died over the roughly 2.5 million years that dinosaurs lived.

For the first time, the team also calculated the longevity of the dinosaur. Using scientific literature and expert opinion, they estimated that the probable age of sexual maturity of a T. rex was 15.5 years, and that its life span could be as long as 20 years. The average body mass of an adult dinosaur was about 5,200 kilograms, and growth in sexual maturity could cause it to reach 7,000 kilograms.

From these calculations, the team concluded that each generation of T. rex lasted about 19 years, and that there was one dinosaur for every 100 square kilometers.

Study can help to understand the change of a species

The researchers also determined that, with a population of 20,000 dinosaurs and some 127,000 generations of the species, there would be a total of 2.5 billion dinosaurs.

The researchers’ methods “appear to be very informative, while also showing the current limits of what can be done with what we know now,” said Jason C. Poole, chief fossil preparation officer at the Bighorn Basin Paleontological Institute and artist. paleontological, which was not part of the study.

“I am sure it will open the doors to further address the issues of population density and what this means over time,” Poole added in an email. “So this could really help to understand things like the change of a species over time in relation to evolution and changing ecosystems,” he added.

The study authors estimate that the population density of the species equaled 3,800 of the carnivorous dinosaurs in an area the size of California, but only two in an area the size of the city of Washington.

T. rex fossils are unusual

On the other hand, the results also allowed the authors of the report to determine that only fossil remains of T. rex are conserved in a proportion of 1 in 80 million.

‘The great impact of this study may be that it shows how rare fossils are. In the sense that they only represent a small fraction of the individual organisms that existed, not to mention the depth of time, as in what happens in a few thousand to a million years, “said Poole.

“In a way, this has been a paleontological exercise in how much we can know and how we get to know it,” said Marshall, co-author of the study and professor of integrative biology and of Earth and planetary sciences at UC Berkeley, in a statement. .

“It is amazing how much we really know about these dinosaurs and, from there, how much we can calculate. Our knowledge of T. rex has expanded a lot in recent decades thanks to more fossils, more ways to analyze them, and better ways to integrate information about the many known fossils, ”he said.

Beyond T. rex

Ibrahim also pointed to other possibilities derived from this study.

“There are many things we do not know about the physiology, behavior, and feeding ecology of the tyrannosaurus, but this study offers an interesting approach to estimating the abundance and conservation rate of dinosaurs,” he said.

‘I would love to see it apply to other known dinosaurs from abundant fossils. Looking at a broader range of dinosaurs – predators and prey – might allow us to better compare the animal communities of the age of dinosaurs with modern ones. ‘

“But we are only looking at the surface, and even with this intriguing study, there is still a long way to go before we can confidently apply such approaches more widely to the study of dinosaurs,” he added.

CNN’s Kristen Rogers contributed to this report.

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