Almost all modern grazing animals live in herds or large family groups, and there is no reason to suppose that dinosaurs were any different. Animals living in herds are able to alert each other to the approach of threatening predators, so this behaviour helps with survival.
Fossil footprints show us that plant-eating dinosaurs travelled in groups made up of both large and small individuals. Sometimes large groups of fossils of the same species are found tumbled together. Scientists think that sometimes a herd may have died when overwhelmed by a flood, for example when crossing a river.
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