In the recent Walking Dead #111 - from Robert Kirkman, Charlie Adlard and Dave McCaig - a fan writes in asking about zombie physiology. Specifically, they want to know what happens after a zombie consumes human flesh. Can the undead digest what they eat, and what happens once they're full? Kirkman's answer exposes the gross truth.
In response, the Walking Dead creator writes that in his mind, his zombies are "always pooping," constantly excreting their human victims. It's a grim truth of the franchise that eating humans doesn't even seem to give the Walkers sustenance. See below for Kirkman's full comments.
Walking Dead's Zombies Are "Always Pooping"
The Reveal Has Darker Implications Than It Seems
I like to think they're always pooping... undigested bits of flesh... it just passes right through. Fun!
As haunting as it would be to live in a world where the undead stalk you as prey, it's even darker to imagine the zombie horde constantly relieving itself as it goes, adding a gross edge to the zombie horror. This fact suggests that the zombies aren't just predators but a potential biological disaster zone, especially in large numbers. While the early comics show small groups of Walkers, later events like the Whisperer War reveal groups that are thousands strong - on that scale, constantly pooping zombies could constitute an environmental disaster, unleashing a wave of bacteria and parasites in their wake.
Walking Dead has always been one of the more practical explorations of the end of the world, as the focus on survivors working to create new societies and scrape by in a ruined world asks some very practical questions about the mechanics of survival. However, a few hardcore Walking Dead obsessives aside, Kirkman's reveal about the zombie digestive system is probably insight most fans could have done without.
The Walking Dead #111 is available now from Image Comics.