Warning! Some of the replies contain major spoilers.

A study was published concerning butterfly mutants. 12 percent of the butterflies which were exposed to radiation as a larva, carried deformities. In the third generation the number rose to 34 percent.

Further studies will be conducted on different species, because the effects of nuclear accidents are still widely unknown.

You'll find the full scientific report there:

http://www.nature.com/srep/2012/120809/srep00570/full/srep00570.html

Meh. I was hoping for some human eating monsters like cazadores in New Vegas.

ARGH Cazadors. I had to resist the temptation to fry Dr. Boros in Old World Blues for bringing Cazadors and Nightstalkers into the world.

Oh yeah, so I guess Cazadors aren't actually nuclear mutants. Neither are Nightstalkers, Super Mutants, or Deathclaws, for that matter.

NONE of the mutated creatures in the original Fallout games are actually nuclear mutants, though. Almost every monster in FO1/2 is due to FEV, even radscorpions and manti and the like. (Except for maybe the wanamingos, I'm not really sure what's up with them.) The radiation itself isn't really responsible for much other than dampening the effects of the background FEV that pervades the west coast area. It's the virus that's ultimately responsible for all the huge monsters.

Oh yeah, that's true. i was thinking Radscorpions and Radroaches were nuclear, but you're right. Does that mean Ghouls are the only actual nuclear mutants? Or are they FEV too? I dont remember.

I think that most of the ghouls are nuclear, or at least they're described that way. That would make the most sense, as the ghouls in Necropolis were created because their Vault door wouldn't close, so they were directly exposed to the radiation. They'd have acquired a LOT of radiation before they ever had a chance to get exposed to FEV. On the other hand, Harold became a ghoul (or at least a ghoul-like creature) due to heavy FEV exposure. So I'm not really sure. I think it's in the Fallout Bible somewhere.

Yeah, I think you're right. From what I remember reading, Harold became his tree-growing self due to being exposed to FEV either in a smaller dosage or over an extended amount of time (I don't remember which), which is why he didn't become a Super Mutant. Is it ever stated whether Harold was a Ghoul or human beforehand?

Oh, and what exactly are Floaters, anyway?

EDIT: Oh, and on the Ghoul matter, Raul also talks about being turned into a Ghoul via radiation in New Vegas. Apparently it's gradual, no a big "whoomph"

I knew a guy who turned into a ghoul due to radiation, and when i asked if FEV had anything to do with it, he told me to kiss his butt, which then fell off.

What about the geckos in toxic caves?

I don't have any particular info one way or another, but I'd have to assume they're also FEV. They're larger/tougher/stronger versions of a pre-War creature, just like the manti and scorpions and deathclaws and supermutants and rats and spore plants, which are all FEV-mutated. They follow the pattern.

Centaurs were specifically created by the Master as well (and, incidentally, were creepier in FO1&2 imo). The real question though is what are Floaters? Some undersea thing?

At first I thought snake, but on reflection I think they'd have to be some sort of arthropod. Like an inchworm, maybe.

Hm, yeah, that sounds plausible. I guess they developed an air sac thingy to help them float?

Couldn't say. I've only just started with this game. But inchworm was the only thing I could think of which moves quite like that, and the squishy farty thing that shoots out kind of looks like a bug-head with antennae on it.

Come to think of it, I've also seen caterpilars that look like a bit that, and sort of move the same.