Actually this reminds me: Do zombies show up on thermal
Great question!
It depends on the type of zombie folklore.
Voodoo type zombies (Weekend at Bernie's II) have more of a mystical powersource that's reanimating the dead bodies...so I'd say no thermal signature.
"The Virus" trope type zombies on the other hand are simply human beings that have been transformed by a mutagenic contagion of which the origins can be:
-viral (28 Days Later, 28 Weeks Later, Quarantine, Resident Evil, etc),
-nanorobotic (Metal Gear Solid 4 Guns of the Patriots, Red Faction, etc),
-an extraterristerial parasite (Night of the Creeps, The Thing, Slither, X-files, Silent Hill, Star Trek TNG, etc),
-biochemical (DC2 from Planet terror),
-or mysterious radiological contamination (Romero's Night of the Living Dead).
Viral, and nanorobotic make the most plausible sense to me since these can actually be targeted at specific changes in DNA, while biochemical and radiological mutagens simply damage/mutate all the DNA and only by super rare chance will the correct "zombie code" be set.
And since these type of "zombies" are still physical, corporeal, non-mystical,
biological beings that actually can be killed via total-incineration, or extreme CNS damage...I'd say thermal signature exists.
But even if "The Virus" mutates their bodies to generate such a low body temperature (for metabolic efficiency reasons) that blends their thermal signature into the background thermal radiation, it is still a moot point.
WHY?
Because the AC130 doesn't track by thermal night vision alone.
It has the AN/APQ-180 radar system that tracks air and ground targets beyond visual range to close range in all weather types, night or day.
Also keep in mind the AC130 can do day-missions and track by normal visual tracking along with the radar.
Since zombies tend to rove in hordes (which is the main reason why these contagious zombies are so dangerous regardless of their slow or fast speeds) their radar and visual signature will be huge....you'd have to be blind not spot them.
But with all that said, I don't believe in zombies lol.
The movie Quarantine, and 28 days later is somewhat realistic since these "zombie viruses" were based off of the rabies virus symptoms which causes encephalitis of the brain leading to extremely violent behaviours, paranoia, hallucinations, psychosis, and death.
Also in theory when medical nanorobotics are developed in the future...it is theorized that it can be used for gene-therapies more effectively than simply modifying viruses as a DNA carrier/vector. So nanorobots can theorhetically either mutate your genes and turn you into a zombie or affect your mind into becoming a mindless "zombie horde" (Metal Gear Solid 4).
Oh and as for the extraterrestrial parasite thing...I don't believe in aliens either.
Damn I wrote alot...hope it wasn't a wall of text for you guys. I tried to space things out a bit.