In the ancient western part of North America, during the Jurassic Period, being big was crucial for survival. A recent study by scientists focused on bite marks left by meat-eating dinosaurs on the bones of sauropods, massive plant-eating dinosaurs with long necks, tails, and strong legs. The researchers examined about 600 bones from at least nine types of sauropods and discovered deep grooves on 68 bones from 40 individual sauropods. Contrary to what one might think, these marks weren’t from predators attacking live adult sauropods. Instead, the scientists suggested that meat-eaters found the bodies of sauropods that had already died from things like old age or sickness. It seemed too risky for even large predators to take down adult sauropods, which were much bigger than them. The study suggests predators may have preyed on weakened sauropods, the largest land animals that lived from around 200 to 66 million years ago.

Smaller theropod dinosaurs in the Jurassic Period, such as Allosaurus and Ceratosaurus, coexisted with sauropods. Despite their size, these theropods didn’t target adult sauropods; instead, evidence suggests they mainly preyed on young sauropods. The study proposes that the abundance of young sauropods provided a reliable food source for these theropods, indicating a preference for vulnerable prey in the Morrison Formation.