This is What Life Would Be Like if T. rex Roamed Today’s Earth

Despite being one of the most well-known and popular dinosaurs, we are still learning things about the Tyrannosaurus rex today. Scientists have recently discovered that T. rex likely originated in North America rather than Asia, which was previously thought.

Let’s imagine for a minute that somehow T. rex survived the mass extinction of dinosaurs that occurred 66 million years ago when a large meteor hit the Earth. How would a T. rex survive in today’s world? Would people take safaris to view T. rex in its natural habitat, like we do apex predators, such as lions? Or would we live in constant fear of being eaten or trampled? Could the climate even support such a large animal?

T. rex: Size and Behavior

Before we imagine T. rex in today’s world, let’s take a look at how T. rex lived. T. rex was a fearsome predator, reaching 12 feet high and 40 feet long. Scientists estimate T. rex weighed around 11,000 to 15,500 pounds or more. That’s a little heavier than the average African elephant (today’s largest land animal), which weighs around 12,000 pounds. At 12 feet, T. rex was also slightly taller than an African elephant, which typically stands 10 to 11 feet at the shoulder, though the largest males can reach up to 13 feet.

It’s hard to imagine how fearsome a massive elephant would be if it hunted live prey rather than munching on grass and twigs. Through fossil markings, scientists know that T. rex hunted live prey and swallowed pieces whole. The dinosaur couldn’t use its hands to eat, and it didn’t chew. So it ripped off pieces of flesh and bone. Then swallowed them whole, using its neck muscles to flop its head back and move the food to the back of its neck. This is called “inertial feeding,” and it’s what birds and crocodiles do today.

As for what was on its diet, probably just about anything it came across. Scientists have evidence it probably ate a diet of plant-eating dinosaurs, such as Edmontosaurus and Triceratops.

What Would Be on T. rex’s Diet if It Lived Today?

Evidence suggests that T. rex ate other large dinosaurs. For example, Triceratops is estimated to weigh up to around 17,000 pounds, which is similar to or slightly heavier than the largest T. rex specimens. We don’t know exactly how dinosaurs’ metabolism worked. However, scientists estimate the T. rex’s metabolism may have fallen somewhere between that of a crocodile and a warm-blooded predator. Imagine our fictional T. rex weighs 13,000 pounds and needs to eat 15% of its body weight each week to survive. In this case, it would need about 1,950 pounds of food. That equals about two humans per day.

What we know of T. rex is that they were opportunistic feeders, hunting down whatever came into their path. We can probably assume a T. rex today would eat a variety of food, including crocodiles, lizards, and mammals. By studying fossilized stomach contents, scientists have found that juvenile T. rex ate smaller prey. The grown adults feasted on large plant-eating dinosaurs. The younger dinosaurs were faster and more agile. They could catch quick-moving prey, while the adults focused on large, but slower-moving meals. Scientists have even found evidence that T. rexes feasted on each other.

We can imagine if T. rex roamed North America today, not only would humans be on the diet, but so would livestock such as cattle, pigs, and sheep. Farmers would have to protect their farm animals from more than just coyotes and foxes. If T. rex lived in Africa or Asia today, it’s easy to imagine it would regularly hunt large herbivores such as rhinos and elephants.

What Was the Climate Like for T. rex?

T. rex lived in the Late Cretaceous period, probably around 90 to 66 million years ago. The Cretaceous period was when flowering plants began to grow and create diverse ground habitats.

New research suggests T. rex’s ancestors came from Asia to North America on a land bridge. T. rex evolved from those early dinosaurs in North America. Fossils have been found in Montana and South Dakota, as well as in Alberta, Canada. When T. rex roamed through what is now Montana and South Dakota, it was not the current semi-arid climate with hot summers and cold winters. It was closer to a floodplain in Louisiana. The climate was warmer, and plant life was lush and diverse. Dinosaurs were able to grow to large body sizes in the warm climate.

Scientists have learned that after an event called the Cretaceous Thermal Maximum (CTM), atmospheric greenhouse gas levels and global temperatures dropped. This created a climate where some groups of dinosaurs, such as the T. rex, were better able to thrive than others. While some dinosaur species died out due to cooling temperatures, species such as T. rex and megaraptors could tolerate the colder weather. They filled the empty space and grew to enormous sizes.

Where Would T. rex Live Today?

Although the end of the Cretaceous period was cooler than it had been previously, it was still much warmer than today. The world then had a greenhouse climate, and what is the American West today would have been a lush ecosystem. We can speculate that if somehow the T. rex had not died out, it may have migrated south to warmer climates, perhaps living in Florida or Louisiana today.

Assuming the T. rex began its migration after the land bridges no longer existed, it would be trapped in North and South America. Although we often imagine dinosaurs traipsing through tropical rainforests, in reality, the size of T. rex would have made this nearly impossible. Large herbivores kept the land clear and open with their huge diets of plants. A T. rex could not have navigated well in a dense forest with close tree trunks, but needed open space to move.

It’s possible that today’s modern environment, where humans have cleared forests to make room for civilization, would be an ideal open area for a T. rex to roam. Although people would have had to devise not only earthquake and hurricane-safe buildings, but structures strong enough to withstand a T. rex attack. We can imagine T. rexes may have roamed the American South, where the climate is warmer. It likely wouldn’t stick to heavily forested areas, but would probably prefer open areas where it hunted livestock and probably humans as well.

Could Humans Control T. rex?

If alive today, the T. rex, like other apex predators today, would be a wild and unpredictable animal. Assuming that humans evolved in the same manner and had modern-day technology, it’s possible that humans would have hunted T. rex to smaller numbers. It might be endangered species today.

Perhaps we would keep them in sanctuaries, and people would pay to view them, such as an African safari. However, is it even possible to keep such a large and predatory creature contained? It’s possible that escapes from T. rexes could occur. They were known to have a strong sense of smell and would probably be drawn to farms and meat factories, creating havoc and destroying farmers’ livelihoods.

Despite the massive size of a fully grown T. rex, humans would likely fear the younger, smaller, and more agile juveniles even more. If people had to run and hide from a T. rex, we would have a much better chance of evading the slower adults than the agile, but smaller juveniles.

Would Altitude Sickness Be a Problem?

As fun (and scary) as it is to imagine a world where a T. rex roams free, the reality is that the climate was such a different place that it likely couldn’t survive today unless it could adapt. Air bubbles trapped in amber from the Cretaceous period have shown that the atmosphere was rich in oxygen. Would T. rex be gasping for breath as it chased its prey?

T. rex likely breathed in an atmosphere with about 25-35% oxygen. Today, our atmosphere contains about 21% oxygen. This would be a similar feeling for us to be at Pikes Peak. And yet, people have successfully adapted to living, and even exercising, in high-altitude areas with less oxygen, so there’s no reason to think dinosaurs might not be able to either.

An Endangered Species

If T. rex were alive today, living alongside humans, we can imagine humans would have done their best to control their populations for their own survival. After all, T. rexes would be a danger to humans and our livestock. Would a small number of T. rexes remain, kept in sanctuaries or zoos? Would T. rexes be in danger of poachers for some body part, just like rhinos are killed for their horns and elephants for their tusks? Or would humans never have evolved to develop the civilizations we have today, being constantly on the run from a fearsome predator?