Paleontologists at the University of California, Berkeley, set out to count how many T. rex lived during the Cretaceous – about 65 million to 98 million years ago – knowing that it would not be a simple task.
Fossils have long been used to deepen our understanding of extinct creatures, such as dinosaurs, but experts say it can be a challenge to use these remains to calculate population density and abundance.
“It’s not just information that makes the estimate,” said 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 estimate how many Easter eggs ever existed? It just can’t be done. You need information from somewhere else – for example, the density of Easter eggs, the area over which eggs could be found and how many Easter eggs have been laid in the gardens. “
“Previously, researchers have tried to estimate things like the probable size of the Tyrannosaurus’ household area and its basic energy needs, so this is a neat extension of previous work and includes a lot of up-to-date information about the Tyrannosaurus,” said Nizar Ibrahim. 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 interesting studies come with a certain amount of uncertainty – there are so many that we still don’t know about dinosaurs, even about a Hollywood star like T. rex,” he added. Ibrahim in an email.
20,000 T. rex in North America at any one time
Using fossil records, density data and data from climate models, the UC Berkeley team estimated that approximately 20,000 adult T. rex, which lived throughout North America, probably existed at some point. This, say researchers in a study published in the journal Science, means that about 2.5 billion predators have lived and died in the approximately 2.5 million years that dinosaurs lived.
For the first time, the team also calculated the longevity of the dinosaur: using the scientific literature and expert opinion, they estimated that the probable age of sexual maturity for a T. rex was 15.5 years, and its lifespan could reach up to late 1920s. The average body weight of the adult dinosaur was about 5,200 kilograms (11,464 pounds), and a rapid increase in sexual maturity could send 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, it would be 2.5 billion dinosaurs in general, the team determined.
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 preparer at the Bighorn Basin Paleontological Institute and a paleontological artist, who was not part of the study.
“I’m sure it will open the door to focus even better on population density issues and what that means over time,” Poole added in an email. “So this could help to understand things like changing a species over time, in terms of the evolution and change of ecosystems.”
The study estimates that the population density of the species is equivalent to 3,800 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 report’s authors to determine that only about 1 in 80 million T. rex are preserved as fossilized remains.
“The great impact of this study may be that it shows how rare fossils are, in the sense that they represent only a small part of the individual organisms that existed, not to mention the depth of time, and how much happens in a few thousand to at a million years old, “Poole said.
“In some ways, this has been a paleontological exercise in how much we can know and how we strive to know it,” said Marshall, co-author of the study and professor of integrative biology at UC Berkeley and Earth and Science. planetary, in a statement. .
“It is surprising how much we actually know about these dinosaurs and, from this, how much more we can calculate. Our knowledge of T. rex has expanded so much in recent decades thanks to more fossils, more ways to analyze them, and better ways to integrate information on multiple known fossils, “he said.
Beyond T. rex
Ibrahim sees other possibilities arising from this study.
“There are a lot of things we don’t know about the physiology, behavior and ecology of feeding Tyrannosaurus, but this study offers an interesting approach to estimating the abundance and conservation rate of dinosaurs,” he said.
“I would like to see it applied to other known dinosaurs from abundant fossils. Looking at a wider range of dinosaurs – predators and prey – could allow us to better compare the animal communities of the dinosaur era with the modern ones.
“But we’re just scratching the surface, and even with this interesting study, there’s still a long way to go before we can confidently apply such broader approaches to the study of dinosaurs.”