Blood scapes would get removed on map load in 3.62. Sami fixed that.
If blood gets on a surface and dried/coagulates, it takes more than some rain to wash fully off. Scrubbing, bleach or baking soda et cetera.
Tracking wounded elk (traffic collision) if there’s open wound and blood; it’ll stay visible for several days on the roadside. (And on bushes, trees...)