A number of animals grow to twice their normal size. This doubles each animal's height, length, and width, increasing its weight by a factor of eight. This increase in size has a number of effects:
Hit Dice: The creature's HD double, doubling the creature's base attack bonus and increasing its saves accordingly.
Size: The creature's size increases one step. This increase reduces its AC (according to the new size), reduces its attack bonus (according to the new size), affects its ability to grapple, and so on. The creature gains an enlargement bonus to Strength and Constitution scores, and its damage with natural attacks increases. This spell does not affect Colossal creatures.
When the spell ends, the creature's hit points return to normal, and all damage the creature has taken while enlarged is divided by 2.
The spell gives the character no special means of command or influence over the enlarged animals.