T. rex's Behaviour
Some things we know about T. rex, and some things we want to know. Behavior research is one of the most fun areas of paleontology, because it brings extinct creatures "back to life." Scientists use living animals as T. rex models, and they start to paint a picture of what life was like 65 million years ago.

This section is still under development. Thank you for your patience.

  Predator or Scavenger?

One of the biggest debates: was T. rex hunting, or snacking on the already-dead? Although so many theropod teeth are found throughout excavations of prey animals (like Triceratops or duckbills), that's not enough to say whether T. rex was eating something it killed...or something it found.

This is a fun argument, because it allows us to evaluate some of T. rex's most impressive parts. A brain packed with the capacity to smell well, see with precision and in three dimensions; a body with legs that could outrun prey, with deadly teeth and claws for killing, and an efficient breathing / circulatory system meant to fuel an athlete. T. rex certainly had the equipment.

Today's scavengers act as excellent models - and these models show that no large-bodied creatures rely solely on scavenging! Hyenas, for example, kill more than they plunder. Only vultures rely mostly on scavenging (but they'll kill, too, when they're hungry enough), and they are built differently - with wings to cover lots of territory, no binocular vision, and a not-so-great ability to smell.

The fossil record also proves this point: "the one that got away." In The Denver Museum of Nature and Science, a duckbill dinosaur is on display with a healed bite mark at the base of its tail. Triceratops specimens also have been found with similar healed injuries - injuries that could not have been made in the Cretaceous by anything besides T. rex's mouth. Remember: the fact that these bites were healed means the animals were alive when they were attacked!

Even worse: a few cases of T. rex cannibalism have been discovered. Not only does it seem that T. rex was a killer, apparently no one was safe. Scientists have found at least two instances where T. rex vertebrae were sheared in half, and the parts where T-bone and tenderloin steaks would have been were missing. No one else had the jaws to do it.

Sue's crime scene also preserved some interesting information. Black Hills Institute workers found fragments of three other T. rexes, one of which was a lower leg that was sheared in half - the fine scratch marks matched the serrations of a T. rex tooth. In related news, Sue's skull shows the unmistakable marks of another T. rex, who literally ripped off part of the left side of her face. Maybe her skeleton was preserved (and not eaten), because the perpetrators had filled up on those other T. rexes with her.

'You know,' he added very gravely, 'it's one of the most serious things that can possibly happen to one in a battle - to get one's head cut off.' - Lewis Carroll, Through the Looking Glass

Keep in mind, though, we don't have to limit our thinking to predator or scavenger. Most creatures will eat what they can get; this is known as opportunistic feeding. Just like a lion will snack on a free, already-dead, smelly meal if it finds one - or a vulture will kill if it's hungry enough - we suppose T. rex wasn't choosy. Predator or scavenger? YES!

  Loners or Pack Members?

Long considered the Curmudgeon of the Cretaceous, T. rex is getting a new reputation. Still not a social butterfly, like the duckbill Edmontosaurus - who are found together in the thousands - T. rex may be just a bit of a family man. Or woman, as the case may be. The proof? On several occasions, scientists have discovered parts of more than one T. rex in the same excavation site. For example, Sue was buried with skull and leg bones from a smaller, gracile sub-adult and two youngsters. This would indicate that T. rex did not travel alone.

Other examples, besides Sue: a T. rex adult-juvenile pair at the Los Angeles County Museum, where the juvenile had once been misidentified as Gorgosaurus; a new multiple-specimen site in Montana that is still unfinished. Excavations of some of the earliest theropods revealed adults and young trapped together. Triassic Aged sediment at Ghost Ranch, New Mexico, preserved articulated adult Coelophysis skeletons with partially grown juveniles. Disarticulated remains of a closely related form, Syntarsus, of the Jurassic of South Africa, were found in a bonebed of adults and juveniles. An Albertosaurus site in Canada preserves the remains of at least eight individuals. A newly-discovered site in South America revealed at least seven Giganotosaurus relatives in the same bone pile.

  Eggs & Babies

Who could imagine that any creature would lay two eggs at the same time? As in, the exact same time, and plant them in the soil in pairs. That's what all theropod egg nests show: sometimes a dozen, sometimes more than two dozen of eggs, poked into the ground in twos, in circles. Although no one has found a T. rex nest, egg, or embryo, scientists surmise that the largest-of-all dino eggs - up to the size of a loaf of French bread in a nest as large as nine feet in diameter - are very similar to what T. rex must have laid.

This unique laying pattern allows us to glimpse inside the long-gone soft tissues of T. rex. That is, once we compare the bodies of their closest relatives - crocodiles and birds - we see similarities and differences in both egg-laying systems. From this, and the fossil evidence, we see that - like crocodiles and unlike birds - T. rex laid its eggs all at one time. And, like birds and unlike crocodiles, it did not cover its nest with sand or vegetation.

While we may never watch a T. rex lay eggs, we have found fossilized Oviraptor and Troodon parents sitting on their nests, caught in the act of incubating their eggs. Some day, maybe we'll find a T. rex trapped in a sudden storm - forever protecting its fossilized nest of eggs.