Paleontologists at the University of California, Berkeley, set out to put a number on the number of T. rex that lived during the Cretaceous period (about 65 to 98 million years ago), knowing it would not be an easy task.
Fossils have long been used to deepen our understanding of extinct creatures like dinosaurs, but experts say it can be a challenge to use these remains to calculate population density and abundance.
“There’s simply no information to make the estimate,” explained Charles Marshall, director of the University of California’s Paleontology Museum, which was part of the research team. “If you find an Easter egg in your garden, how can you calculate how many Easter eggs there have been? It just can’t be done. You need information from somewhere else, for example, the density of Easter eggs, area on which eggs could be found and for how many years have Easter eggs been laid in the gardens “.
“Previously, researchers have tried to estimate things like the probable size of the tyrannosaur’s domestic surface and its basic energy needs, so this is an extension of previous work and includes a lot of up-to-date information about the tyrannosaur,” he said Nizar Ibrahim, a paleontologist at the University of Portsmouth (UK) and National Geographic Explorer, who were not part of the research.
“We just have to keep in mind that all these intriguing studies come with a certain dose of uncertainty: there are so many things we still don’t know about dinosaurs, even a Hollywood star like T. rex,” Ibrahim added to an email.
20,000 T. rex in North America at a time
Using fossil record, density data, and climate model data, the UC Berkeley team estimated that approximately 20,000 adult T. rex, living throughout North America, probably existed at any time. This, according to researchers in a study published in the journal Science, means that about 2.5 billion predators lived and died during the approximately 2.5 million years during which dinosaurs lived.
For the first time, the team also calculated the longevity of the dinosaur: using the scientific literature and the opinion of experts, they estimated that the probable age of sexual maturity of a T. rex was 15.5 years and the its useful life could reach the end of the twenties. The average body mass of the dinosaur was about 5,200 kilograms (11,464 pounds), and a growth boost at sexual maturity could bring them to 7,000 kilograms (15,432 pounds).
From these estimates, the team concluded that each generation of T. rex lasted about 19 years, with one dinosaur per 100 square kilometers (38.6 miles).
With a permanent population of 20,000 dinosaurs and about 127,000 generations of species, there would be 2.5 billion dinosaurs in general, the team determined.
The researchers’ methods “appear to be very informative while showing the current limits of what can be done with what we now know,” said Jason C. Poole, chief fossil preparer at the Bighorn Basin Paleontological Institute and artist. paleontological, which was not part of the study.
“I’m sure it will open doors to focus even more on population density issues and what that means over time,” Poole added in an email. “So really this could help to understand things like the change of a species over time in relation to the evolution and change of ecosystems.”
The study authors estimate that the population density of the species was equivalent to 3,800 of the carnivorous dinosaurs in an area the size of California, but only two in an area the size of Washington DC.
T. rex fossils are rare
Meanwhile, the results also allowed the authors of the report to determine that only about 1 in 80 million T. rex are preserved as fossilized remains.
“The big impact of this study may be that it shows how rare fossils are, as they only represent a small fraction of the individual organisms that existed not to mention the depth of time as it happens in a few thousand to a million years, ”Poole said.
“Somehow, this has been a paleontological exercise in what we can know and how we know it,” said Marshall, co-author of the study and professor of integrative biology at the University of Berkeley and the Earth and Planetary Sciences. , in a statement. .
“It’s amazing how much we actually know about these dinosaurs, and from that, the more we can calculate. Our knowledge of T. rex has expanded a lot in recent decades thanks to more fossils, more ways of analyzing it.” the and best ways to integrate information about the multiple known fossils, ”he said.
Beyond the T. rex
Ibrahim sees other possibilities derived from this study.
“There are many things we don’t know about the physiology, behavior, and food ecology of the tyrannosaurus, but this study offers an interesting approach to estimating the abundance and rate of preservation of dinosaurs,” he said.
“I would love to see it applied to other known dinosaurs from abundant fossils. If we examine a wider range of dinosaurs (predators and prey), we could afford to better compare dinosaur-age animal communities with the modern ones.
“But we’re just scratching the surface, and even with this intriguing study, there’s still a long way to go before we can safely apply these approaches more broadly to the study of dinosaurs.”