The German researchers based their findings on freshly-eaten remains in the stomachs of T-rex adults. In some cases, the prey was so small that it had been swallowed whole.

'Even modern predators prefer old and sick animals or inexperienced young individuals,' the researchers write. 'These are an easy prey to bring down and the risk of injury for the predator is much lower. This strategy was probably the same in dinosaurs.'

It is also highly possible that Tyrannosaurus ate his own offspring.

'Finds of dinosaur nesting sites indicate that they contained large numbers of eggs which should have resulted in a high number of offspring. But little of this is reflected in the fossil record. Juvenile dinosaurs are surprisingly rare -- maybe because many of them have been eaten by predators. Hopefully there will soon be more evidence to help us really understand the theropods' hunting behaviour,' he added.