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Tyrannosaurus rex was so large and heavy that it鈥檚 easy to assume that the . But, paradoxically, it might have used those tremors to its advantage: the shape of its feet suggests the seismic waves from each footfall remained similar in intensity as it approached its prey, acting as a weird form of camouflage.

Heavy animals produced earthquake-like seismic waves with every footfall. We know that other animals detect those seismic signals: and low-frequency vocalisations.

Large dinosaurs must have produced seismic waves too. Ernesto Blanco at the University of the Republic, Uruguay, and his colleagues decided to explore how they might have been harnessed. They analysed a total of 64 fossilised footprints left by several large dinosaurs including herbivores, omnivores, and carnivorous theropods 鈥� a group that includes T. rex.

The researchers says that theropods typically had elongated feet with a length-to-width ratio of 2, while omnivorous and herbivorous dinosaurs had feet with a length-to-width ratio closer to 1.

Making waves

Blanco and his colleagues simulated the pattern of seismic waves generated when the dinosaur feet hit the ground. They found the waves produced by theropod feet were weakest in the walking direction: in other words, theropods had a foot shape that would have allowed them to sneak up on their prey while 鈥榮eismically鈥� masking their presence.

In more detail, some seismic waves generated by theropod footfalls did travel forward 鈥� towards a potential prey target. But the simulations suggest that the intensity of those waves was essentially the same once the carnivore was within 25 metres of its target. Blanco and his colleagues think this adds to the idea that theropods could sneak up on their prey undetected using what they have dubbed 鈥榮eismic wave camouflage鈥�.

Blanco suggests that the elongated feet could have evolved precisely because they should have given theropods a hunting advantage, although he says the idea will need to be tested in more detail.

鈥淪o far, there is no evidence of a modern animal using this camouflage,鈥� says Blanco. 鈥淏ut it is a new concept. So perhaps it鈥檚 because nobody was looking for it before.鈥�