Zombies

Zombies, also called Walkers and/or Geeks by T-Dog and Glenn, are the main non-human antagonists of The Walking Dead.

Basic Info
The zombies are the classic slow walking Romero style zombies, which originated in Night of the Living Dead. Following classic Romero-rules, everyone who dies, for any reason, will re-animate as a zombie. Even someone killed by a gunshot wound with no zombies involved at all will re-animate as a zombie. Zombie bites are not how the "infection" is spread. Instead, zombie bites and saliva cause infections that are 100% lethal. Characters have speculated, but cannot confirm, that whatever causes zombies to re-animate is some sort of virus that everyone in the world is technically infected with but is only triggered by death.

It is known, however, that upon death, it can take anytime between eight minutes and eight hours for the corpse to reanimate.

The zombies out-number humans 5,000 to 1.

Behavior
Besides eating humans, zombies have been shown eating the horse Rick used to reach Atlanta, rats in Atlanta`s sewers, a deer in the woods outside the original survivor camp, and apparently Hannah's dog (according to Andrew, the dog was mutilated by a zombie). This also follows one of the variants of classic Romero-style zombies: some zombies from other science fiction narratives actively prefer to eat only human brains, or more generally, try to eat any part of a human but ignore animals. Romero's more realistic rules, established in Dawn of the Dead, are that zombies are just compelled to attack and try to eat any "warm bodies" they come across, regardless of whether they are humans or animals.

Zombies in the TV series somewhat differ from their comic book counterparts, but do share a hand full of characteristics. Zombies from both sides have small fragments of memory of their past life. This can be seen when Rick visits Morgan for the second time. Morgan ' s son, Duane was bitten, and the way Morgan explained it, zombified-Duane looked at Morgan strangely, like he knew him (this could, however, simply be Morgan's own imagination as the loss of his son almost mentally ruined him; or perhaps it could be the docile nature zombies tend to experience when they have been exposed to a particular person for a long period of time). Though both zombies may share the trait, it is obvious that memory is much more prevalent in the minds of the walkers from the TV show rather than the comic series due to the more common examples.

The biters from the comic and show (more so in the latter) display limited problem solving intellect and understanding of their surroundings, as one outside the mall took a rock to the glass door, knowing it would be effective. Whether or not this concept of smart(er) zombies will be dropped altogether, or explored further as the series enters its second season is unknown.

As far as eating habits go, zombies in both the TV show and the comics seem to only have an attraction to warm, fresh meat. Some of the more picky individuals will even neglect or hesitate to eat meat that is only a few hours old (like the Governor's daughter, Penny). Rotting or processed meat (like canned ham) will be ignored altogether. It is unknown whether or not consumed meat is digested in some way or simply continues to rot within the stomach (both explanations could explain the lack of tissue remains of the ground squirrel eaten by a walker in the forest of the TV series). If the meat is digested however, and serves in some way as fuel, it could explain how some walkers have not yet rotted while others have decomposed to the point of immobilization. Seeing how the virus (or whatever the cause of reanimation is) restarts the central nervous system and the muscles within the body, as well as the majority of sensory organs (eyes, ears, sense of smell, etc.), the idea of it restarting the digestive system to some extent might not be too far fetched.

Types
Zombies are separated by the survivors in the following groups:

Roamers
Roamers or Walkers are known to "roam" around looking for food. They are the most commonly encountered kind of zombies.

Lurkers
Lurkers are the zombies that just sit around playing "dead" until someone reaches them and they bite them. Lurkers can be the real threat because they can pass as dead zombies. One of them was responsible for Allen's death and Dale losing a leg.

The Herd
As described by Dr. Eugene Porter, a herd is when zombies act with a mob mentality. One zombie might brush his hand on a door knob and another will see this and mistake it as an attempt to get in. Then he will beat on the door to get in, and the first zombie will see this and try to get in. This will spark a chain reaction.

Biters
Alice, Dr. Stevens' assistant in Woodbury mentioned that her original group of survivors refered to the zombies as "biters," because while some do lurk and some may roam they all will bite and to classify them into separate groups is a silly practice. Biters are just regular zombies, and Woodbury citizens just happened to call them as that name.

Weakness
Zombies are only vulnerable to massive brain damage, (i.e. shooting in the head). The heads of decapitated zombies remain active until destroyed. Despite still moving, zombies still decompose as regular corpses. The zombified Hannah, encountered by Rick Grimes outside of the hospital appeared to be immobilized after some kind of decay. Zombies are shown to become frozen, but one had thawed out enough to almost bite Glenn. In Issue 55 a zombie attempted to grab Rosita, yet it lacked the strength to keep his hold, pull her or stand up. This may be a sign that zombies will eventually decay to the point where they are no longer a threat to humans which would mean that the outbreak will eventually end on its own accord.

Zombies seem to differentiate living humans from the undead via smell. Rick and Glenn are able to walk through an infested city to search for supplies after covering themselves in a zombie's entrails. Michonne is also able to walk vast distances without being mobbed probably due to the fact the two defenseless zombies she kept near her dampened her scent. However due to the disgusting odour and the possibility of it washing off it doesn’t make it very practical for everyday application.

Kirkman wrote:
 * "[Zombies cannot usually go up stairs]--it's decided on a case by case basis...I'm sure there's a zombie out there who could...but not very well...to reference this series--was it issue 8? Rick opens the door to the basement of that house--and zombies are waiting at the top of the stairs and rush him!...So based on that scene...zombies can go up stairs... but it probably took them a while."

Despite this quote from Kirkman, two zombies are shown pursuing Rick down a flight of stairs in the hospital in Issue 1 and both of them manage to use the stairs with no problems. Furthermore, in Tell It to the Frogs, an entire group of zombies are able to walk to the top of the staircase outside of which Merle is chained. Of course, going downstairs might be easy compared to walking up, and it could have taken the zombies some hours to climb up the stairs.

Strengths
Zombies main advantages over humans is that they do not need to sleep, eat or breathe. This allows them to slowly follow the survivors around in perpetuity (or until they decay to the point of no longer being mobile or otherwise threatening).

Reanimation
There are many ways a person can become a zombie:

Infection
This is the most common way a person can become a zombie. The bite of a zombie is shown to cause a powerful and lethal fever. Symptoms shown include:


 * Extreme warmth
 * Hallucinations
 * Vomiting
 * Pale skin
 * Delirium
 * Sensitive bones

However, zombie bites don't carry the virus. They simply cause lethal infections. Thus, a person can become a zombie from dying of any cause other than brain damage.

According to Jenner, a corpse can reanimate between eight minutes and eight hours after death.

Robert Kirkman wrote:
 * "...the rule is: WHATEVER it is that causes the zombies, is something everyone already has. If you stub your toe, get an infection and die ... you turn into a zombie. UNLESS your brain is damaged. If someone shoots you in the head and you die ...you're dead. A zombie bite kills you because of infection, or blood loss ... not because of the zombie "virus.""


 * This does not seem to be the case with walkers in the TV show. During the second season as the group is stopped on the highway, there are multiple dead and decayed bodies that do not reanimate.  While they could have brain trauma, it seems unlikely there were no reanimated dead buckled in the cars.

Amputation
As shown in the case of Dale, a person can survive a zombie bite if the limb which is bitten is amputated. Althought, he's the only person who had survived. Amputation were tried on Morgan Jones and Allen, which both failed.

Evolution
Robert Kirkman wrote that "Romero's evolving zombies are his spin. Mine just keep rotting."

Zombie animals
For some reason animals are not affected by the phenomenon, but it is unknown whether or not the survivors are aware of this, because the animals encountered are eaten whole. Kirkman has stated there are no zombie animals.

Trivia

 * In Issue 38 Robert Kirkman writes there is "ONE zombie who's appeared no less than three different times in the book"
 * Michonne kills a zombie going into a car with a t-shirt that says "Youngblood"
 * In the TV Series, some of the survivors, notably T-Dog and Glenn, refer to the zombies as "geeks".
 * In the TV Series, the zombies are shown mainly in Guts and Bloodletting to run at a jogger's pace.
 * In the TV Series, the zombies can apparently use tools. This is shown in Guts, where a zombie is using a rock to smash open the department store doors.
 * As with most forms of undead horror fiction, the word, "zombie" is almost never said by characters in the series. According to Robert Kirkman in episode 2 of Talking Dead this is because in the world of The Walking Dead the works of George A. Romero were never made and zombies do not appear in fiction.

Credited Zombies

 * Addy Miller as Little Girl Zombie, the little girl found at the gas station in Days Gone Bye.
 * Brian Stretch as Tank Soldier, the undead soldier in the tank, from Days Gone Bye and Guts.
 * Joe Giles as Black Suited Zombie, the zombie wandering in the street when Rick emerges from his empty home in Days Gone Bye.
 * Melissa Cowen as Bicycle Girl Zombie/Hannah, the half-zombie crawling in the park in Days Gone Bye.
 * Max Calder as Baseball Bat Zombie, the zombie that Rick kills with a baseball bat in Days Gone Bye.

Characters That Turned In Order (Comic)

 * Hannah
 * Jim
 * Shane Walsh
 * Shawn Greene
 * Julie
 * Chris
 * Rachel Greene
 * Susie Greene
 * Andrew
 * Penny Blake
 * Dr. Stevens
 * Otis
 * Caesar Martinez
 * Carol Peletier
 * Tyreese
 * Lori Grimes (In Rick's Dream)
 * Ford's Daughter
 * Duane Jones
 * Jessie Anderson

Characters That Turned In Order (TV-Series)

 * Hannah
 * Jenny Jones
 * Leon Basset
 * Wayne Dunlap
 * Jim
 * Amy