They are made to attack humans regardless if they are prey or predators. Created by Gaou, they are corrupted animals with violent malice and will attack anything that moves or anyone at all. When he invaded Nico Garden he turned most of the animals into garugaru but Nico sealed them into eggs which were a temporary measure at best. Then, they scattered into Animal Town. When they are inside the egg they will hatch eventually and start rampaging. Garugaru doesn't have to be from Nico Garden any animal can be changed into one.
