A time when both egg and the brooding parent are permanently at risk.
Smaller Oviraptors are no more than a nuisance.
Larger predators are a different story.
Unwilling to leave the nest,
the adult protects its offspring, first, by hiding...
and if that fails, it goes on the offensive.
Protecting the nest means Gigantoraptors' young are more likely to survive.
It now seems clear that the instinct to nurture
and care for a nest of eggs had its origins with the dinosaurs.
It's a behaviour that was so successful it's still widespread today with birds.
But the fossils show something else.
These animals all died sitting on their nests.
It seems that the threats don't always come from predators.
Sometimes the real danger comes from the most unlikely places.
These dinosaurs were all buried alive.