Tyrannosaurus rex was one of the largest and fiercest predators to ever walk the Earth. Even just the thought of coming face-to-face with one of these enormous killing machines is enough to send chills down your spine.
But what exactly did these huge theropod dinosaurs eat to sustain their giant size and dominate their ecosystem?
If you’re short on time, here’s a quick answer to your question: Tyrannosaurus rex was an apex predator that likely fed on large herbivorous dinosaurs such as Triceratops and Edmontosaurus.
Dietary Composition
Primarily Carnivorous
Tyrannosaurus rex was undoubtedly an apex predator during the late Cretaceous period, equipped with massive jaws and teeth ideal for grabbing and tearing apart large prey (Osborn, 1905). Multiple lines of evidence, from stomach contents to bite marks on fossils to biomechanical modeling of its skull, indicate T. rex lived mostly by hunting live animals.
Numerous T. rex skeletons have been excavated over the past century. In a few rare cases paleontologists discovered the fossilized remains of an animal in the stomach cavity of the skeleton that had likely been the T. rex’s last meal (Chin et al., 1998).
Examples include the dinosaur fossils of triceratops, ankylosaurs, hadrosaurs, and even smaller tyrannosaurs inside T. rex stomach cavities (Horner, 1994). This directly points to T. rex being a predator.
In addition, bite marks and damage caused by the giant jaws of T. rex have been identified on many dinosaur fossils from the Hell Creek Formation. Scientists have matched these bite marks and punctures to the size and shape of T. rex’s serrated teeth (Erickson et al., 1996).
T. rex was likely biting these dinosaurs in efforts to kill and feed on them.
Finally, computer models of T. rex’s skull, jaw muscles, and teeth reveal it had one of the most powerful bites in the animal kingdom. It was capable of exerting over 12,000 pounds of force with its back teeth – easily enough to crush bones and pierce thick hides (Bates & Falkingham, 2012).
This evidence again supports the notion that Tyrannosaurus was well-adapted for tackling live, large prey.
Occasional Scavenging
While Tyrannosaurus rex appears best adapted for live prey hunting using its keen senses and devastating bite, some evidence suggests it may have supplemented its diet through scavenging kills made by other predators.
Analysis shows that some bite marks on Edmontosaurus and Triceratops fossils believed to be from T. rex have started healing, indicating the prey survived the initial attack (Fowler & Sullivan, 2011).
This opens up the possibility those animals eventually succumbed to injuries or infection and were later scavenged by a T. rex. Additionally, tooth scrapes linked to feeding have been identified on large armored ankylosaurs and the thick-skinned nodosaur Borealopelta, suggesting T. rex may have fed on their carcasses (Carpenter, 2000).
A few genetic studies propose the olfactory bulbs in T. rex’s brain were relatively small compared to dedicated hunters. While its sense of smell was still sharp, T. rex may have spent more time patrolling territory visually and using its keen eyesight to scavenge carcasses killed by others (Stevens, 2006).
This behavior would have provided T. rex access to more calories with less energy spent hunting.
Ultimately an apex predator the size and strength of T. rex likely took any opportunity it could to feed its immense appetite, whether actively hunting down live prey through forests and floodplains or occasionally scavenging from carcasses it came across while patrolling its territory.
All lines of evidence point toward T. rex having been a devastatingly efficient and flexible carnivore.
Feeding Behaviors and Strategies
Powerful Jaws and Teeth for Killing Prey
Tyrannosaurus rex had a massive head and powerful jaws lined with serrated teeth up to 30 cm long. These adaptations made T. rex an incredibly efficient predator. Its bite force was the strongest of any terrestrial animal, estimated at over 8,000 pounds per square inch, enabling it to easily crush bone and bite through flesh (1).
T. rex could swallow up to 500 pounds of meat in one bite! Additionally, its teeth were continually replaced throughout its lifetime, with some estimates of over 2,000 teeth grown over 25 or more years (2).
With such powerful weapons, T. rex likely employed a “bite-and-hold” strategy against large prey like Triceratops or Edmontosaurus. It would sink its teeth into the prey animal’s body, holding it firm while its victim weakened from blood loss and trauma.
Smaller or more agile prey were likely swallowed whole (3).
Prey Choice and Hunting Techniques
The prey of choice for T. rex seems to have been giant horned dinosaurs like Triceratops and duck-billed hadrosaurs like Edmontosaurus. Analysis of coprolites (fossilized feces) confirms that T. rex fed on these animals (4).
Incredible finds like a T. rex tooth embedded in a Triceratops tailbone and a T. rex with an Edmontosaurus bone in its guts provide direct evidence of these predator-prey relationships (5).
T. rex likely employed ambush tactics when hunting, using its color vision and keen sense of smell to detect prey at a distance. Despite its massive size, some evidence suggests T. rex may have been capable of bursts of speed up to 10-25 mph, not quite enough to run down prey over a long distance but adequate for ambushing unsuspecting victims (6).
While an adult T. rex likely had little to fear from competing predators, juveniles and babies were at risk from other carnivores like Tarbosaurus or Daspletosaurus. This may explain why juvenile T. rex remains have been found in groups – they may have hunted in packs for protection (7).
Prey Animals | Hunting Tactics |
Triceratops, Edmontosaurus, Ankylosaurus | Ambush, bite-and-hold |
Smaller ornithopods, early theropods | Swallow whole |
Typical Prey Species
Large Ceratopsians like Triceratops
One of the most favored meals of T. Rex was the large ceratopsian dinosaur Triceratops. Sporting three sharp horns and a bony frill around its neck, Triceratops was a dangerous prey, though evidence shows successful T. Rex hunts.
Massive tyrannosaurs like Sue could have delivered a crushing bite to a Triceratops’ frill or flank, targeting its vulnerable areas. Websites like American Museum of Natural History showcase Triceratops and T. Rex fossils locked in mortal combat.
Hadrosaurs Such as Edmontosaurus
With their abundance across North America and less formidable defenses compared to ceratopsians, duck-billed hadrosaurs were another staple prey item for T. Rex based on bite marks and coprolites. A 2016 study details a T. Rex attack on a large Edmontosaurus, with the predator’s broken tooth lodged in the hadrosaur’s tail bone.
Ankylosaurs and Pachycephalosaurs When Available
Though their bony armor and small size would have made them more difficult to attack, Tyrannosaurs still fed on armored dinosaurs when the opportunity presented itself. Ankylosaur specimens show healed bite marks matching T. Rex, and some fossils preserve T. Rex teeth next to Pachycephalosaurus remains.
Scavenging after other predators or singling out injured/young individuals may have allowed T. Rex access to these dangerous morsels.
By employing a bone-crushing bite force of over 8,000 psi, T. Rex gained access to a variety of prey in its environment. It likely hunted opportunistically, targeting less-defended animals like hadrosaurs whenever possible, while attempting to overwhelm formidable ceratopsians and eventually scavenging – few animals could resist becoming lunch for this apex predator!
Competition with Other Predators
Mapusaurus
The Tyrannosaurus Rex lived during the Late Cretaceous period, between 70-66 million years ago, alongside other large theropod dinosaurs like Mapusaurus that may have competed with T. Rex for food and territory.
Mapusaurus was one of the largest carnivorous dinosaurs, measuring over 40 feet long and weighing around 6 tons. It inhabited what is now South America. While smaller than T. Rex, Mapusaurus likely hunted many of the same prey animals and would have been in direct competition for resources.
Fossil evidence shows Mapusaurus hunted in packs, unlike the solitary T. Rex. This pack-hunting behavior may have given Mapusaurus an advantage over solitary predators in taking down very large prey. The competition between Mapusaurus and T. Rex demonstrates how different predatory strategies evolved among theropods.
Albertosaurus
Albertosaurus was a close relative of T. Rex that lived slightly earlier, during the late Cretaceous Period around 70 million years ago. It inhabited many of the same areas as T. Rex, including what are now the western United States and Canada.
Albertosaurus was smaller, averaging around 30 feet long and 1.5 tons. It had a similar body shape and set of teeth specialized for crushing bone and tearing flesh. Due to the anatomical similarities and overlapping habitats, Albertosaurus and T. Rex likely competed for the same food resources.
Fossil evidence shows that both theropods hunted hadrosaurs and ceratopsians. However, the later and larger T. Rex likely had an advantage and outcompeted Albertosaurus, leading to its extinction before the KT mass extinction that wiped out all non-avian dinosaurs.
Daspletosaurus
Another close relative of T. Rex was Daspletosaurus, often called the “small tyrant lizard” due to its anatomical similarities to its larger and more famous relative. Daspletosaurus lived around 75-71 million years ago in western North America.
Adults grew up to 26 feet long and weighed around 1 ton, making it noticeably smaller than adult T. Rex specimens. It had many of the same features as T. Rex, including rows of serrated teeth, muscular jaws, and relatively short two-fingered forelimbs.
The two tyrannosaurids likely hunted many of the same prey species, including hadrosaurs, ceratopsians, and possibly primitive mammals. Daspletosaurus may have filled an important niche as a small to mid-sized predator between the larger T. Rex at the top of the food chain and smaller predators like Troodon below it.
Conclusion
In conclusion, Tyrannosaurus rex was well-adapted for a lifestyle primarily focused on taking down large herbivorous dinosaur prey through the use of its massive head, strong jaws, bone-crushing teeth, and reasonably intelligent hunting strategies.
It dominated its ecosystem not only through its sheer size and strength, but also through competition with smaller tyrannosaur species.