It can be snapshotted, when also using Replenishing Ravager. If you set your minimum ferocity to be rank 1-4 = 2, rank 5-9 = 3 and rank 10+ = 4, then go to town and come back, but change the skill rank to something else, it won’t change the minimum ferocity it will remain as it was until you go to town again, doesn’t matter.
Basically you can make use of it by setting the skill as high rank as what ever min rank you get, and it will stay as that, even if you remove almost all skill points, Replenishing Ravager must still be on.
Replenishing Ravager basically doesn’t allow the skill to drop or lower, besides town visit, maybe just teleporting also works.
Removing the Replenishing Ravager fixes it, then ferocity minimum and maximum changes retroactively, when changing between 4 and 5 skill ranks.
When using Prodigy’s Edge that gives 4 extra skills points to purchased active skills, that doesn’t work with Ravager too, doesn’t matter if using 1 point or with(out) any of the 3 extra skill links. The skill description changes, but the ferocity amount doesn’t change, unless you actively use or remove a skill point somewhere in the skill tree, that’s the only way to get extra ferocity to update itself, also if you do get it to increase it also won’t drop, until well you adjust any skill by a point or go to town.