The thorny devil-like Calcarisaurus is a small, thorny reptile with a near impregnable hide. Despite its small size, few bigger predators bother the plucky little tank out of respect for its battery of spurs, which cover almost every surface of its body. A secreted irritant along the edges of Calcarisaurus spurs help to drive home its message of inedibility to the curious or stupid.
Such a solid defense grants Calcarisaurus impunity to wander the island without fear of molestation by carnivores. As a result, its eyesight and hearing are poor, having little need for those senses to alert it to danger.
Smell is the principal sense of Calcarisaurus and it is used to track down small lizards, rodents (like Skull Island rats), and large invertebrates in the scrub and other open regions. Centipedes are a particularly favored prey and are excavated from their burrows by Calcarisaurus with its strong digging claws. The bites of the Skull Island centipedes do not worry the lizard-like reptile.
One larger predator alone is a threat to Calcarisaurus. Venatosaurus, intelligent and adaptable, has developed strategies for flipping its prey to expose the vulnerable, less heavily armored underside, restricting Calcarisaurus to regions where the greater predators seldom roam.