A Feral Walker is a type of zombie which was removed in Alpha 2 due to being a copied model another infected from a different zombie game that was repainted. This sparked a law-suit, so it was quickly removed.
Someone stole the 3D model of a zombie from another zombie game , re-repainted it, then put it on the Unity asset store as their own model for sale. Earlier in development, Fun Pimps bought a few assets as placeholders from the Unity store, one of which was this zombie. They were then contacted by the other zombie game creators and were then asked to remove it from 7 Days To Die.
They only appeared in the Burnt Forest Biome and therefore were replaced by the Burnt Zombie.
They walked slightly faster than other types.