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Ask the researchers

Ask the researchers

How do scientists know whether dinosaurs hunted or ate animals that were already dead? (Antonio Olivieri, 6 years old, via Facebook)

Eduardo CesarMight it be that the Tyrannosaurus rex, the giant of the predator dinosaurs, with just over 60 teeth in its mouth, actually took advantage of what other animals hunted instead of capturing its own prey? This discussion has been keeping paleontologists busy for a century and it changes as knowledge advances. One clue indicating that the T. rex were not very good hunters is the equivalent length of the bones in their hind paws – the femur and the tibia – which made them poor runners. Even so, there are signs that they did attack large dinosaurs, as a fossil of an Edmontosaurus indicates. This has the marks of a partially healed bite in one of its vertebrae, indicating that a T. Rex had tried to kill it (but failed). Two major difficulties stand in the way of finding a definitive answer to the T. Rex’s feeding habits: the scarcity of complete dinosaur fossils and the rarity of exclusive carnivores among the animals living today. The only one is the vulture, whose sense of smell is ultra-sensitive. It can also fly over huge distances to find food. The most likely thing is that T. Rex was able to capture even large prey, provided it did not have to run very far, and without its disregarding the carrion it might have found along its way.

Luiz Eduardo Anelli
Institute of Geosciences of the University of São Paulo