When the full moon first rises, his mouth starts growing out within the span of an excruciating 10 minutes, and his pupils start to appear.
In his second stage, his whole body is hunched over and his feet and hands are more webbed and claws are sharper. He throws mindless tantrums in this stage, wrecking everything he sees and eating anything thats alive.
In his third stage, his sanity is regained and his mouth starts retracting, while bleeding painfully. Though in this stage, he gets the chance to actually speak.
Extra facts:
He spends approximately 6 hours in the bathtub. Well, he doesnt have much better to do and he loves water.
Even though he doesnt have a mouth on the outside you can hear him yell/scream or angrily groan at you sometimes.

Questions: How does he breathe?
He still has a nose, its just not drawn here. Its just like two small holes anyways.
How does he eat when hes not on his...lunar cycle?
The things eaten from his lunar cycle stage are stored in his belly for the month. I mean he eats ALOT during his lunar cycle, it causes his belly to expand a bit temporarily. He often gets belly aches after the lunar cycle. :P
...Mating?
...........Lets just say No.

Also: Basically keep your mouth shut and make all the expressive sounds possible. Thats all he can do as far as communication goes during the month. xD

HES ADORABLE

Omg the sounds I just made.