In 1971, a fossil was found that captured a Velociraptor mongoliensis clutched around a Protoceratops andrewsi in Mongolia. It is believed that they died simultaneously, while fighting, when they were either surprised by a sand storm or buried when a sand dune collapsed on top of them.

The large eyes of Protoceratops has been suggested as evidence for a nocturnal lifestyle. However, subsequent comparisons between the scleral rings of Protoceratops and modern birds and reptiles have indicated a more cathemeral lifestyle, being active throughout the day during short intervals. This suggests that the fight between Protoceratops and the primarily nocturnal Velociraptor indicated by the fighting specimens may have occurred at twilight or under low-light conditions.