The Tyrannosaurus rex is perhaps the most iconic of all the dinosaurs, immortalized in movies, children’s toys and silly Halloween costumes. The name translates to ‘king of the tyrant lizards’, and the terrifying profile makes it clear why: T. Rex had a massive head, powerful jaws, razor-sharp teeth and a whip-like tail. (Though his bad arms are a comic contrast to the rest of his face.) The T. Rex is believed to have been one of the largest land meat eaters of all time, more than 40 feet long and 12 feet long at the hips.
But like many extinct animals, it is difficult to know how much of a threat the T. Rex was during his reign. (Notably, there has been debate for years as to whether T. Rex was a predator or scavenger, although recently the scientific consensus has been toward predators.) Were they as common as rabbits, or very widespread predators like snow leopards?
A group of scientists led by Charles R. Marshall, director of the Museum of Paleontology, University of California, just wanted to answer that question. They believe they can now estimate approximately how many T. Rexes have roamed the planet.
Their estimate is about 2.5 billion specimens that have roamed the earth collectively during their existence, lasting several million years. (They would probably have lived more generations if it had not been caused by a meteor or comet 66 million years ago).
The researchers, who published their findings in Science Magazine, estimate that the numbers of T. rexes in a given period were about 20,000 individuals and that they lived about 127,000 generations. To put it in context with today’s predator populations, the number of 20,000 is comparable to the current African lion population, which according to conservationists is at 25,000.
The scientists reached their estimate using a wide range of data. First, they took into account a principle known as Damuth’s Law, which states that species with larger body size usually have lower average population densities. Because this formula includes individuals in a species that have not reached their maximum size, the scientists used an estimate for ‘postjuvenal individuals’ – the T. Rex equivalent of an anxious teenager. (Now there is a sobering thought.) Once they had the information, they multiplied it by the estimated geographical area where paleontologists believe the monstrous beast once wandered. They then recorded what we know about when the T. rex lived, although the scientists admit that this figure is particularly unclear “due to the poor temporal control in most T. rex fossil areas and because there is a large dinosaur conservation gap among the oldest T. rex fossils. “
Since experts believe it is based on fossil evidence that they lived 1.2 million years to 3.6 million years, the team determined the average figure to be 2.4 million years. From there, they plugged in other numbers until they finally came to their estimates.
Despite their short rule over the planet – one that was unfortunately cut short by the Cretaceous Triassic Frontier Extinction event – the fact that another bipedal predator would count them 66 million years later speaks to their cultural immortality.
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