Let's first cover the different types of undead and their diets:

Vampires -- drink blood

Zombies -- eat the flesh of the living

Mummies -- are well perserved, often still containing the food they ate before they were mummified or were given a big stockpile of food perserved in little urns in their tombs (this is so they can take some snacks with them to the Underworld)

Ghouls -- eats dead people (usually a living human being or, according to the ancient Arabic folklore they are demons who eat people)

Now let's cover their dining habits:

Vampires -- bites into a nice vein to extract the blood from their victims, usually on the neck or sometimes on the wrist, usually depicted with blood stains or trails of blood dripping from their mouths (do they NOT have napkins or wet naps available for Vamps?)

Zombies -- just rip off limbs, sink teeth into flesh usually while a victim screams from pain, tears off raw flesh, devours the goriest flesh available, makes a big mess and keeps coming back for more

Mummies -- don't really eat anything

Ghouls -- relish digging into dead flesh and sometimes even have sex with corpses while doing it (it's a ghoul thing)

Eventually what goes in has to go out, right?  Only unless there's some kind of supernatural explanation that defies convention.  But that just sounds like a cop-out to me.  I suspect the following:

From what I know about Vampire folklore is that Vampires were originally reported as bloated in appearance and ruddy, purplish or dark in colour, like big human-shaped ticks filled up with blood.  The blood they drank didn't leak out of the body, but seeped out of it, so to speak.  They were nasty creatures, not romantic at all, and didn't often kill their victims, their victims basically being relatives or lovers they had when they were alive.  At some point, the Vampire stories evolved into the Hollywood romantic types who couldn't go out in daylight, were frightened by garlic and crosses, and liked to neck hot chicks.  From what I can tell, Vampires use the blood they suck (because they don't exactly drink it, do they?) to keep their bodies from getting stiff.  Blood lubricates their muscles, but on a more spiritual level, the "life is in the blood" and therefore what Vampires really feed on is life.  Therefore Vampires don't exactly poo, they may leak from too much blood sucking, I suspect, or they may be like Vampire bats who, because they are on a strictly liquid diet, frequently urinate.

Zombies, before they were adapted by George A. Romero, were reanimated corpses.  According to African-Carribean Vodu folklore, zombies were raised from the dead by powerful sorcerors to be workers.  Zombies were originally controlled and didn't eat much of anything because why not have some undead workers you don't have to provide for in the first place?  That was the whole point of having them around.  At some point it was more interesting to play on human fears about death and corpses even more and create a kind of zombie that chased after the living in order to eat, hurt, and kill them.  Isn't it much more terrifying to see a zombie out of humanity's control?  So Zombies, according to the movies, are not under anyone's control, are usually brought back into animation by supernatural or scientific means, and their main goal is the hunger for living human flesh that drives them out of the grave.  In the Romero films, the culprit was radiation leaking from a satellite returned from an orbit of Venus.  This special Venus radiation affects all recently unburied dead, making these undead especially invulnerable.  In the most recent Romero zombie film, Land of the Dead, the zombies still seem to retain memories of being human and have enough intelligence to do simple tasks, but their hunger for living flesh overcomes any sympathy they might try to learn.  It is my firm belief that zombies do have to poo, and they may even have to puke, but they lack the sense to clean up after themselves.  The act of eating is too powerful.  They must smell horrible.  That's something not often depicted in the movies -- wouldn't you smell a zombie coming?  That is something to think about when you're trying to survive hordes of zombies invading your hometown!

With that said, Mummies who come back from the dead, I believe, are fueled by a more supernatural means to keep them going.  Do I have to go further into that?  I mean, come on, they are usually dry, brittle, slow moving, but can inflict harm on the living with spiritual power.  Usually Mummies come back because some idiot raided their tomb.  So if a living human being gets killed by a Mummy, it's usually their fault.  It's a corpse's revenege on a graverobber.  Mummies don't eat their victims so they don't have to poo.

Ghouls, on the other hand, most definitely have to poo.  Ghouls are usually living beings, not zombie or vampire, and most definitely demonic in the sense that they are possessed by a lust for dead things.  So I'll have to scratch that category because, technically, they aren't undead.

What do you think?

I wrote this while listening to Yngwie Malmsteen.  A guilty pleasure I developed while in high school and have never been able to shake off.  I love old school metal.  I love long haired guitarists with fast hands and big egos.  It's been a very funny experience listening Malmsteen's music while writing about the undead.  I think I need to get away from the keyboard now before I get even more silly.  Not that you were required to know that to enjoy this blog post, but it does say something for the kind of mood I'm in tonight!