Cubivore is a life development simulation taking place in a world populated entirely by animals. Starting with a basic life form, players test Darwin's theory of evolution by attacking and then consuming lesser creatures while avoiding predators. Once eaten, the victim's abilities will contribute to the player's evolutionary process. Conquering different animals results in changes to one's agility, mobility, strength, or fierceness. As players roam the 3D lands looking for prey, they will eventually encounter boss creatures. Only by defeating them in combat can players become master of the region.

Conquering a boss not only results in the acquisition of new skills, but a character also becomes ready to mate in order to continue the bloodline. Play then begins anew as the creature's offspring, whose starting abilities reflect the overall strengths of its parents. In addition to the unusual premise, Cubivore features a distinctive visual presentation unlike any previous GameCube title. Each creature is made up of flat-shaded squares or tiles, with different colored squares representing eyes, noses, ears, and mouths. Released in Japan as Doubutsu Bancho, which roughly translates to "Animal Leader" in English. ~ Scott Alan Marriott, All Game Guide