Its believed these pokémon can see their lives flash before their eyes at a regular basis, hence why they were historically misclassified as psychic type. Their x-rays are visible when they charge up, and it isn't uncommon for them to seemingly return from the dead.
Carnivine that evolve into gourfrond acquire a craving for more than just bugs. The taste of blood drives them mad. The internal acids of a gourfrond can dissolve bone, and even types of metal.