Why exactly was that Triceratops so ill? Michael Crichton’s novel supplies an answer. It is explained that the dino lacks suitable teeth for chewing and so, like birds, would swallow rocks and use them to grind food in its digestive tract. After six weeks, the rocks would become too smooth to be useful, and the animal would regurgitate them. When finding new rocks to use, the Triceratops also swallowed toxic berries.