Animal Growth/Reduce

When this spell is cast, you causes one animal, within a 5" square area to grow to twice their normal size. The effects of this growth are doubled hit dice and doubled damage in combat. The spell lasts for 2 melee rounds for each level casting the spell. The reverse reduces animal size by one half, and likewise reduces hit dice, attack damage, etc. If the target is unwilling, it can make a Constitution saving throw. On a success, the spell has no effect

At a higher level increase the amount of animals effected (1 per level) and double duration time.