Wild Shape
This class feature works like the polymorph spell, except that wildshape is a supernatural ability that works only for the druid using it. It cannot be shared with the druid's animal companion (or other creature with the share spells quality) because it's a supernatural ability.
The duration is 1 hour per druid level or until the druid resumes her normal form. Changing form (to animal or back) is a standard action and doesn't provoke an attack of opportunity.
At 11th level and below, the druid can assume only animal forms; the size of the animal form to be assumed depends on the druid's level, as noted in the druid class description. Since the power duplicates the polymorph spell, the druid gains the assumed form's extraordinary special attacks, but not its extraordinary special qualities. For example, a druid wildshaped into a wolf gains the wolf's trip attack but not its scent ability. The druid's level determines what size animal form the druid can assume.
At 12th level and above, a druid can assume plant forms of the same sizes as the animal forms the druid can assume.
At 16th level and above, a druid can assume elemental forms, with the druid's level limiting the size as noted in the druid class description. A druid that takes elemental form retains her own creature type, but gains all the elemental's extraordinary, supernatural, and spell-like abilities (both special attacks and special qualities), and also gains the elemental's feats. Since the druid does not gain the features and traits of the elemental type, the druid does not gain the elemental's immunity to poison, sleep effects, paralysis, and stunning. The druid also does not gain immunity to critical hits or flanking. On the bright side, the druid retains the ability to be raised or resurrected, provided that the druid could be raised or resurrected in the first place.
Alternate Form
This supernatural special quality works much like the polymorph spell; here's an overview, with the differences between the alternate form ability and the polymorph spell called out.
- Unlike polymorph, the creature is limited to the assumed forms specified in the creature's description.
- Unlike polymorph, the creature retains the type and subtype of its original form. It gains the size of its new form.
- The creature loses the natural weapons, natural armor, movement modes, and extraordinary special attacks of its original form. The creature gains the natural weapons, natural armor, movement modes, and extraordinary special attacks of its new form.
- Unlike polymorph, the creature retains the special qualities of its original form. It does not gain any special qualities of its new form.
- The creature retains the spell-like abilities and supernatural attacks of its old form (except for breath weapons and gaze attacks). It does not gain the spell-like abilities or supernatural attacks of its new form.
- The creature gains the physical ability scores (Strength, Dexterity, Constitution) of its new form. It retains the mental ability scores (Intelligence, Wisdom, Charisma) of its original form.
- Unlike polymorph, the creature retains its hit points and save bonuses, although its save modifiers may change due to a change in ability scores.
- Unlike polymorph, the creature does not regain any lost hit points from changing form.

- The creature retains any spellcasting ability it had in its original form, although it must be able to speak intelligibly to cast spells with verbal components and it must have humanlike hands to cast spells with somatic components.