There is that, yes. I suspect that also explains why most of the people in Snowdin tend to be the kind of monsters with a lot of warm, heavy fur.

[Poor Ice Wolf, standing out there without any pants on.]

[Let's face it: monster biology is weird. Besides, even if the cold wouldn't harm her as much as the average, smaller spider monster, that doesn't mean it's fun.]

Hm. Do you mean mutations as in, say, albinism? Or is this a different meaning my world isn't familiar with?