Decayed Mother

 is one of the different variants of Zombies. These mother zombies died and turned long ago, evidence of this being the fact that their bodies are highly decomposed. Although they're still walking in search of humans to kill.

Combat
These Zombies are normal zombies with not a whole lot of hp's or damage, but like all zombies they can stun you and cause trouble in groups. The Decayed Mother zombie can spawn anywhere and usually is found in Day 7 hordes as well.

During night, the running behaviour is standard as all other zombies. If distance or sheer zombie numbers aren't a concern, scoring a headshot when it's running headfirst towards you can be slightly easier.