Blood temperature
Version 0.12: This article may not be up to date for the latest stable release of Crawl.
Blood temperature is a trait of all monsters which have blood (most natural, non-insect, -arachnid, -jelly, or -eyeball monsters). This trait has little impact on actual gameplay, except for the fact that cold-blooded creatures are slowed if hit by a frost attack.
From mon-util.h:
M_COLD_BLOOD = (1<<16), // susceptible to cold, // drainable by vampires M_WARM_BLOOD = (1<<17), // no effect currently, // drainable by vampires