So you're a zombie (sorry to hear that, by the way). You have your daily routine; shamble, moan, be always on the lookout for live human flesh. And when that flesh appears, you and every other zombie in a hundred-mile radius will converge on it in one enormous mass of undeath.
But surely you're not satisfied with that, are you? There's not even close to enough to go around. One human divided among one hundred zombies is less than a meal.
And yet... isn't there still human flesh all around you? After all, the zombies are "human", just a slightly hungrier type of human, and most of the capacity for reason is gone. You still have to eat. Meat is meat. So what's to stop this horde from feeding on itself?
Ultimately, there is no reason; it just plain doesn't happen, and is left at that. We can only say for sure that there are No Zombie Cannibals. When The Virus creates zombies that are still technically alive, there's no perfectly sensible explanation. Additionally, no matter how ravenous, the zombies will cooperate, instead of fighting over the scraps.
When it is addressed and sketchily justified, it's usually that zombies will only eat living flesh because undead flesh is "not nutritious" or otherwise appealing, The Virus gives them an instinctive sense to go only after uninfected, or that they're supernatural undead, and thus know not to eat each other and instead cooperate. You can certainly argue that rotting flesh wouldn't be terribly safe to eat, but that would bring up the question of why it can walk around in the first place. If they're the brain-eating sort, it's possible they've all been picked clean already.
So ubiquitous it's probably better to list aversions, or explicit justifications. The former count as zombie-specific examples of Monstrous Cannibalism.
- The Marvel Zombies state that not only does zombified flesh taste horrible, it also doesn't sate the maddening hunger the infected feel. Of course, the zombies don't actually NEED to eat, and in most cases have lost the ability to digest food anyway. The hunger is entirely psychological and fades if they're deprived of food long enough. Even alien zombie flesh doesn't help, although alien uninfected flesh is perfectly delicious.
- In Zombies vs. Robots vs. Amazons, the undead will eat each other when no available flesh is present.
- In The Walking Dead, the zombies distinguish between other zombies and live humans by smell. At one point, the protagonists make use of this by slathering themselves with zombie guts in order to walk among them unmolested. They almost never do this again, but, really, considering the lack of bathing facilities and access to clean clothing, are we really blaming them?
- In [REC], all the 'zombies' are controlled by a demon, so it makes them cooperate and even hide. Weapons use was more limited though.
- In the Resident Evil movies, the manual states that zombies chew on the living because they hunger for life, rather than flesh. They last for decades before decaying, with food or without.
- In the tie-in graphic novels that bridge the gap between 28 Days Later and 28 Weeks Later, it's stated that the Infected don't attack each other because they all give off the same pheromone — i.e., they all smell the same to one another, whereas uninfected smell like ordinary people. One character who figures this out survives by finding a way to negate his natural human scent, and later draws a mob of Infected to attack a rival survivor by lobbing a bomb of perfume on him. Why exactly the pheromone stops the Infected attacking one another is never properly explained, though.
- The zombies in Return of the Living Dead series exclusively attack the living because they're convinced that eating live brains can ease the pain of being undead. Or the pain of being dead, the film isn't really clear on which it is.
- In The Zombie Survival Guide and World War Z it is mentioned that Solanum causes the flesh of the victim to become highly toxic. Naturally this does not harm other zombies, but may explain the lack of cannibalism if the toxic flesh smells different. In World War Z many people believe they have witnessed zombie-on-zombie attacks; it is revealed that the victims of these attacks were actually "Quislings", people suffering a mental breakdown caused by the Zombie Apocalypse who believe they are zombies themselves... while other people can mistake them for the undead, the real zombies are not fooled. It's also noted that they don't fight each other because they simply don't perceive anything other than living creatures. A zombie that wants a chunk of human that another zombie wants will keep pulling on it rather than shoving the other zombie away.
- The Extinction Parade, also written by Max Brooks, plays with this by extending the rule to all undead creatures, including vampires. This allows them to become zombie-slaying machines, helped along by their vampiric superpowers and their immunity to The Virus.
- In the Star Wars Expanded Universe novel Death Troopers, the zombies are all controlled by a pseudo-organic hivemind sludge that the Empire was experimenting with. The sludge, called Project Blackwing, is heavily implied to be sentient, and wishes to spread itself as far as possible.
- Justified in Elantris the flesh of the pseudo-zombie Elantrians tastes so terrible that despite their constant ravenous hunger they can't bear to eat each other.
- The zombies in Friday the 13th: The Jason Strain never attack each other or Jason, the Zombie Progenitor, since they seem incapable of registering a fellow undead entity. The same seems to be true for Jason, who is completely apathetic towards the zombies he is creating, his acknowledgement of them never going beyond shoving some aside when they get in his way.
- In Warm Bodies, the Dead must consume living people to take their life force and stay alive, although the implication is that the sparks can actually keep the zombies going just by proximity. They also eat the brains as a sort of high since the brains contain the person's memories, although this is not necessary.
- Hemlock Grove: Upirs cannot feed on the blood of other Upirs because it is poisonous to them. Those affected by the anti-Upir virus become ravenous cannibals who only prey on their own kind.
- Zombies in Dungeons & Dragons and Pathfinder attack living creatures due to an innate hatred for all living things, despite being otherwise mindless — they do not usually eat their victims. Or, depending on the edition, they'll only attack if ordered to do so by their creator but will otherwise not react. The default attack of a human (or elf, or dwarf, or gnome, or halfling, or orc...) zombie isn't to bite, either, it's to smack a target with an arm. Zombies typically only bite if they were animated from a creature that had a natural bite attack to begin with, like a lion or lizardfolk. Ghouls and other "hungry dead" are intelligent, but they crave not only meat, but meat animated and suffused by Positive Energy, the force that, in-universe, sustains and heals all living creatures. The flesh of undead contains the opposing universal force, Negative Energy, and is thus unpalatable.
- In The Smurfs episode "The Purple Smurfs", the Smurfs are becoming angry biting purple creatures due to a weird fly infection. Each purple Smurf bites a blue Smurf at sight but they don't bite each other. This come in play when Hefy disguises himself as a normal Smurf with blue paint (in order to trick Papa Smurf) and another purple Smurf bites him, to his annoyance.
- Not quite zombies, though most of them use similar tactics, but the Titans in Attack on Titan usually do not eat one another, only humans. A few exceptions, however, have occurred:
- In episode 7, a "rogue" Titan appears that ignores humans and kills other Titans but doesn't bother to eat them beyond killing one with its teeth, and in episode 8 a bunch of Titans gang up on him and start eating him alive. Then it turns out that the "rogue" was Eren Jaeger, who is apparently a human that can create and control a Titan body, and has a deep-seating loathing of Titans.
- During the "fall" of Wall Rose, there is an odd moment in which one Titan attacks another, pushing it to the ground and ripping its ear off. The victim of this attack then begins eating its assailant's hand. There has yet to be an explanation for this scene, though considering that the Titans in question were the recently transformed citizens of Connie's village, that could have something to do with it.
- I Am a Hero The ZQN eat humans, each other, and then themselves.
- Crossed are a variant of sentient infected who still retain their higher brain functions but have utterly devolved into textbook psychopaths. If they can't find new victims to torture to death, they'll turn on each other.
- The comic version of Hellgate: London had one of the characters belong to the Cabalists, a separate faction of Bad Powers, Good People who use black magic and the demons' powers against their enemies. She uses her arcane powers to coerce a rampaging horde of reanimated undead into believing there was plenty of food among them and devour each other.
- Strangely enough though, the Marvel Zombies are NOT above fighting each other for the scraps. In fact, pretty much ninety-five percent of the entire horde are destroyed by their leaders (Colonel America and the main five Marvel Zombies present in MZ 2 onwards) when they gain cosmic powers after devouring the Silver Surfer.
- In Night of the Living Dead (1968), zombies do fight among themselves for their meals.
- In ZA: Zombies Anonymous, zombies who refuse to eat living humans are eaten by the cult of zombies who will.
- There are two types of zombies in Silent Night, Zombie Night; the classic shufflers, and a faster and more vicious type that indiscriminately attacks both humans and fellow undead.
- Played for Laughs in Cockneys vs. Zombies: while none of the zombies eat each other or fight over food, they evidently do retain some habits from their previous lives... which, in the case of two herds of zombified Football Hooligans in opposing team colours, includes beating the crap out of each other. Or at least trying to do so; as they're too dim to understand their own transformation, they clumsily punch and shove at one another rather than attempt Removing the Head or Destroying the Brain, and two of them can be seen repeatedly and uselessly stabbing one another in the belly.
- The "zombies" attack each other early on, but this disappears when they develop a hivemind.
- Phoners created after the Pulse has been corrupted are unable to join the hivemind, and as a result they'll gladly attack one another over minor issues, like an argument about a fire truck.
- In Mira Grant's Newsflesh trilogy, (in "Feed," in particular,) we find that zombies prefer to attack the living, but will attack and consume each other if starving.
- Diario de un Zombi has Erico, the lone thinking zombie, explain it's the sensation of life they crave. That said, zombies are dumb as bricks and do eat themselves or others if desperate, confused or angered.
- The Technically Living Zombies of the Black Tide Rising series have no problems with eating other victims of the Synthetic Plague if other meat isn't available.
- The Wraith of Stargate Atlantis aren't strictly zombies, but they do need to eat humans. One episode did show them as capable of endocannibalism, but since they're intelligent that's probably either taboo or just not a good species-survival strategy (the one who did it was stranded and starving).
- The zombies in The Walking Dead hunt by sight and sound, but identify prey by smell. So the movement and sounds made by other zombies will attract them (zombies tend to herd together because of this), but the smell of rotten flesh indicates that other zombies are not desirable as a food source. Two humans were able to walk through a horde of zombies unharmed because they had smeared themselves with zombie guts to make themselves smell rotten — the zombies took notice of them, but did not attack until a rainstorm began to wash the guts (and the rotten smell) away. In at least one instance, the zombies did eat part of another zombie, who was discovered hanging from a tree by Darryl and Andrea after having committed suicide (or, put more linearly, a man hung himself and his body turned into a zombie but the zombie couldn't get down). However, whether the zombies-eating-his-legs occurred before the zombification or after is not specified.
- By season three of Z Nation, edible humans are becoming so rare that starving Zs have begun to avert this trope. Murphy and 10K witness a rolling ball of zombies, all frantically trying to eat one another.
- The name of infamous Death Metal band Cannibal Corpse is an aversion, as bassist Alex Webster has described their name to journalists on at least one or two occasions as "basically a zombie that eats other zombies". Considering that their infamy in an otherwise relatively underground music scene comes from their (sometimes over-the-top) gory albums and songs with titles such as such as "Mummified in Barbed Wire", "A Skull Full of Maggots", and "Entrails Ripped from a Virgin's Cunt", this is an appropriate title.
- GURPS: Infinite Worlds has Gotha-zombies, which do eat each other.
- The fan-made Zombie: The Coil for the Old World of Darkness has two breeds of zombie: Grandes, which can only eat living flesh, and Jackals, which can eat any decayed flesh. This includes other zombies. The two breeds, of course, do not get along. (Sidenote: this book was created several years before Bleach...)
- In Magic: The Gathering, there indeed are Zombie Cannibals. Part of the reason they're common in Magic is because most zombies are aligned with Black mana, which is selfish and pragmatist and defined by sacrifice (even if not necessarily evil), so letting such a tremendous resource such as other zombies go to waste would come across as asinine to most Black mages.
Nothing is sacred to the undead — not even their own kind. — Flavor Text for "Zombie Cannibals".
- In the "Shards of Alara" setting, the shard of Grixis is basically a Zombie Apocalypse taken Up to Eleven. There are only a tiny number of human refugees left who use illusion magic to survive, apparently very effectively. The massive hordes of undead are forced to turn on each other — for example, vampires have to try and drink gross, congealed zombie blood. Poor vampires...
- In Ravnica, Golgari zombies are mentioned to eat other zombies. This way, no nutrients are wasted.
- In Amonkhet some of the White-aligned mummies are seen being destroyed by more conventional Black aligned zombies in Hour of Devastation.
- Cannibal Zombies are mentioned as sometimes killing and eating their own packmates if they are held at bay until sun-up.
- The Weathermay-Foxgrove twins cite the example of a Hungry Dead (ghoul or something related, they weren't quite sure) that became mired in deep mud and devoured its own flesh for lack of anything else to feed upon.
- Shadowrun manages to play this for horror. In the Dark Terrors sourcebook, a datafile talks about an experiment in a secret lab that involved forcing ghouls to feed on the flesh of other ghouls. Not only did they not starve, they thrived... and then started acting as a hive mind. And then started serving as a vector for an elder god only identified as LILITU NOX. The lab and all the test subjects were destroyed, but as the runners reading the file note, the ghoul nation of Asamando has already had to resort to dire, inhumane measures to keep its population fed... and if they turn to eating their own, this possession could happen to an entire country.
- Though it mostly plays this trope straight with the basic slouchers Dead Reign eventually added a variant of zombie that will happily feed on its undead comrades if no living humans or animals are nearby.
- Left 4 Dead averts this in a manner of speaking, considering the infected don't eat people to begin with — when they're not aware of the players, they can be seen fighting each other on occasion. In Left 4 Dead 2 you can make them fight amongst themselves by throwing a jar of Boomer bile onto them, as well. There are also some occasions of Special Infected attacking each other, but this is primarily restricted to AI-controlled Tanks plowing through others because they don't care about tactics or teamwork.
- Often averted in Urban Dead: Zombies attacking each other only gain half the XP they get for damaging human players, but it can still be faster than hunting humans at low levels and is even officially endorsed by some hordes. And they can't permanently kill each other anyways. At higher levels the fact that they attack only humans is simply a consequence of the fact that "they know better than to eat each other" is true on a meta level; they're all controlled by real players.
- In Plants vs. Zombies, while zombies don't normally go for each other, those that eat a Hypno-shroom will.
- There's actually an enemy called a Cannibal in Mass Effect 3 which is a robot-zombie alien which eats different types of robot-zombie alien.
- In Kingdom of Loathing, the Zombie Master challenge path gets several skills that lets them cannibalise their zombie horde. And any of the "normal" game's zombies will still be trying to eat you.
- Doom 3: Averted at one point when you find a zombie gnawing at a corpse's insides, until it sees you and comes after you... and then the corpse also gets up and comes after you.
- Likewise in Dead Island, you may often see a walker chomping down on another downed walker.
- Mostly played straight in Dying Light, although with the justification that the infected know to attack each other by smell. Averted with the Goons and Demolishers, who will kill other zombies while swinging at the player, and with the Bombers, who just destroy everything around them when they explode.
- Zombies are occasionally seen eating other zombies in the (pre-RE4) Resident Evil series. In Resident Evil Code: Veronica, at one point, you find a zombified doctor-torturer feasting on the guts of a previously bagged-up cadaver. When he lunges at you, the corpse shuffles off of the table and joins him in attacking.
- For a given value of 'zombie', those infected with the Demon Virus of Digital Devil Saga must eat human flesh or transform into a mindless demon. Since everyone in the Junkyard is infected (except for Sera), the only people the infectees can eat are other infectees. Until the sequel introduces normal humans.
- In Zombie Ranch these two pages explain that the zombies won't eat each other under normal circumstances, but it's standard practice to recycle destroyed or non market-worthy zeds into feed for the rest of the herd.
- In Unsounded, plods are equal-opportunity scavengers and will go after anything that moves, be it human, animal, fellow zombie, or even themselves. However, their insatiable Horror Hunger responds most strongly to hot, fresh flesh and blood, which is a source of constant Supernatural Angst to the undead Horrifying Hero Duane.
- Awkward Zombie spoofs the Warcraft example with a newly resurrected Undead cannibalizing his own corpse.
- In We're Alive the zombies carry away the bodies of their dead. It is later revealed that they keep stockpiles of human flesh for food and may be eating their own dead.