RadaRadaRada's right, you're taking a net loss of bears there.  I'd much prefer to see a straight conversion.  If you're arguing that some bears die such that the goo can't rez 'em, that should be 1-2 points of frequency at most: that's "blown apart by land mine or shotgun trap" level of damage.

(Player (non-)actions should be separate code, in case anyone's thinking "excessively hunted by the player".  For starters, butchering an animal guarantees it won't rez, so hunting kills should count against zom-critter growth too.)