Zombie dog/doc

Good at catching non-zombie humans, such as the player, and forcing them into battle. Without some terrain or vehicle advantage, the Zombie dog will catch up to you. Upon seeing one, unless the character is well equipped and/or proficient in combat, it is a good idea to retreat to the nearest bush or window and defend there. While this applies to all enemies, it's especially true for zombie dogs as they WILL catch up to the character pretty fast once they detect them. Many inexperienced characters have died from fighting zombie dogs, whether from incapacitating Pain or that Deep Bite--and as a result dying to the subsequent attacks from other zombies or simply infected wounds.

Development history

Early versions of DDA, along with the Whales version, included a "Fresh Zombie" which was capable of catching the PC and forcing him/her into a melee fight, buying time for the rest of the horde to catch up. The Zombie dog is essentially the same critter.