@DragooKnight11

That is an intended feature, some are simply more enthusiastic about their pouncing than others. :P

So my ferrets will randomly die, one somehow managed to launch themselves against the ground at terminal velocity and rip themselves apart.

Yeah, you're trying to use COLOR tokens in a PATTERN object--you have to define the colors separately.

Now I get a different error.
*** Error(s) found in the file "data/installed_mods/kliszfauna (2)/objects/descriptor_pattern_klisz_ferret.txt"
FERRET_SABLE_KLISZ:Unrecognized Colored Pattern Token: NAME
FERRET_SABLE_KLISZ:Unrecognized Colored Pattern Token: WORD
FERRET_SILVER_KLISZ:Unrecognized Colored Pattern Token: NAME
FERRET_SILVER_KLISZ:Unrecognized Colored Pattern Token: WORD

I get an error with one of the graphics.
here is a copy of the error log. https://pastebin.com/iGGg4zXg

Love it. Catsnake for the win.

Just for consistency, because vanilla's domesticated animals don't - I intend to add in wild polecats (as well as polecat men and giant polecats for the savage regions) at a later date.

Is there a specific reason for them to not appear in the wild?

They won't appear in the wild if that's what you mean, but as they're common domestic animals, all civilizations that have access to cats, dogs, horses, etc. will also have them (thus you'll occasionally see elves and humans bringing them for trade, for instance; once Adventure Mode gets released, strays should also appear in human towns).

do they spawn in world gen as well, or just form prepare carefully?