It says nothing about duration, so by the letter of the rules it's the same as polymorph self. I was pretty sure that polymorph self, unlike polymorph other, has a specific duration.
Don't have it in front of me though. Can't confirm.
Wild shape presented in the PHB was based on Polymorph self so the duration was 1 hour/level. However, the revised version in MotW doesn't mention Polymorph self/other so I believe the shape lasts until the Druid changes to a new form.
Sorry, should have been more specific, was referring to the MotW version. The fact that it wasn't mentioned (or duration addressed at all for that matter) in the description is what prompted the question.
