Spiked Skin. When a target hits this creature with a melee attack, it takes 1d4 piercing damage or 1d6 piercing damage if the Dire Hedgegoc is curled up.

Defensive Curl. As a bonus act ionhe Dire Hedgehog curls up into a spiky ball. While curled up, its movement speed is reduced by 10 ft and it has disadvantage on perception checks.
Also when it enters another creatures space, the creature must succeed on a dc 13 dexterity saving throw or take 2d6 piercing damage, or half on a successfull one.
While curled up, the Dire Hedgehog can't use its bite attack, and can end this state as a bonus action.

Bite. Melee Weapon Attack: +4 to hit, reach 5ft ft., 1 target. Hit: # (#d# + #) [damage type] damage.