Still the tyrannosaur hesitated. "What is she afraid of?" Malcolm whispered.

"Probably another tyrannosaur," Grant whispered. Big carnivores like lions and tigers often became cautious after a kill, behaving as if suddenly exposed. Nineteenth-century zoologists imagined the animals felt guilty for what they had done. But contemporary scientists documented the effort behind a kill-hours of patient stalking before the final lunge-as well as the frequency of failure. The idea of "nature, red in tooth and claw" was wrong; most often the prey got away. When a carnivore finally brought down an animal, it was watchful for another predator, who might attack it and steal its prize. Thus this tyrannosaur was probably fearful of another tyrannosaur.