Yes, chickens really can run around with their heads cut off — and Modern Farmer has the explanation behind how the animals can survive decapitation.
The answer often lies in the way chickens are killed — if a butcher slices a chicken's head too high, the slice may miss the jugular veins. A too-high slice can also take away the chicken's forebrain but leave the brain stem and cerebellum, allowing the bird to continue moving and, in some cases, breathing.
Dr. Wayne J. Kuenzel, a poultry physiologist and neurobiologist at the University of Arkansas, told Modern Farmer that chicken skulls have larger-than-normal eye openings, allowing the brain to move higher in the skulls post-slice. "Because the brain is at that angle, you still have the functional part that's so critical for survival intact," Dr. Kuenzel told the magazine.
However, Modern Farmer does have a caveat: "Just because your chicken dances upon impact doesn't necessarily mean that it's still alive." A headless chicken could actually be dead but have nerves that are still moving. "The minute you separate the brain from the neck, just like in humans, you're going to get tremendous movement of the limbs," Dr. Kuenzel says.