Fox shape is not the ability to turn into a fox. Its an alteration of the change shape ability that a kitsune already has. Without having that change shape ability to start with, the feat does nothing.
You can change into a fox in addition to your other forms.
Prerequisites: Cha 13, base attack bonus +3, kitsune.
Special: A kitsune may select this feat any time she would gain a feat.
Benefit: You can take the form of a fox whose appearance is static and cannot be changed each time you assume this form. Your bite attack’s damage is reduced to 1d3 points of damage on a hit, but you gain a +10 racial bonus on Disguise checks made to appear as a fox. Changing from kitsune to fox shape is a standard action. This ability otherwise functions as beast shape II, and your ability scores change accordingly.
This power would give a human with Racial Heritage Kitsune the power to turn into a fox and back as a standard action lasting 1 min per level as this feat acts as the Beast Shape 2 spell that only allows the fox shape. This ruling comes from the lead game designers.