Improved Natural Armor

Your hide is tougher than most.
Prerequisites: Druid Wildshape, Natural armor, Con 13.
Benefit: The creature’s natural armor bonus increases by +1.
Special: When a Druid takes this feat he must select a specific wild shape form. A druid can gain this feat multiple times. Each time the druid takes the feat, he must select a specific wild shape form, its natural armor bonus increases by another point.