Asinus

The Asinus are a hardy group of donkey humanoids that live on Ayr. Their species originated from a number of the human populace adapting to and evolving the more common Donkey Curse into their base physiology. Asinus can shapeshift between a massive beast of burden with incredible strength, and a more humanoid form with donkey-like features. They have a natural compulsion to trade and haul goods, and thus the vast majority of Asinus are traveling merchants, moving their wares between different settlements on Ayr.
  Occasionally, like those afflicted with the Donkey Curse, sometimes an Asinus will just kind of... check out for a while, and wander the fields a bit in their beast forms. Asinus have hearty laughs that often end in a hee or a haw, and find joy in the small things in life.  

As a Playable Race:

Asinus are a playable race. You can find their stat blocks here: Asinus