Ructo is an Antarctosaurus, a large herbivorous dinosaur. He leads and protects a herd residing within Herbivore Paradise, a lush valley sought as a safe haven. His primary responsibility is safeguarding the resident herbivores from external threats, particularly predatory dinosaurs.

He takes on a protective role towards Tops, a young Triceratops separated from his family, within the sanctuary. This protective instinct extends to his entire herd. Ructo's leadership faces a challenge when Gorgo, an albino Gorgosaurus leading a pack of carnivores, targets Herbivore Paradise as hunting grounds. Ructo positions himself against Gorgo to defend the valley and its inhabitants.

Ructo exhibits initial distrust towards Tyrano, a carnivorous dinosaur arriving at Herbivore Paradise with Punon and Tops, due to Tyrano's species and threatening appearance. However, witnessing Tyrano's genuine protective actions towards Punon and Tops, especially against the common enemy Gorgo, shifts Ructo's perspective. He eventually accepts Tyrano's presence, recognizing his non-threatening nature and value as an ally against Gorgo's pack.

During the climax, facing Gorgo's assault, Ructo fights alongside Tyrano and Punon to protect Herbivore Paradise and Tops. This alliance demonstrates his prioritization of the herd's safety over initial prejudices. He participates in the collective effort to repel the Gorgosaurus pack during the volcanic eruption threatening the valley.