Does the AC17 apply to Wild Shape forms?
— John Appleton (@jaa0109) September 16, 2017
Does that mean a dragonborn in Wild Shape wouldn’t have its breath weapon?The dragonborn's racial trait doesn't specify anatomy. The tortle's does.
— Jeremy Crawford (@JeremyECrawford) September 16, 2017
Seriously, that doesnt make a lick of sense. Breath weapons are tied to the natural form There is no general rule on the source of breath weapons, and in the dragonborn, no anatomical source is identified for it.
— Jeremy Crawford (@JeremyECrawford) September 21, 2017
I have to agree with Deaf Buhda on this one. There is precedent that breath weapons are physiological–at least in dragons. Per the 3e Draconomicon, “In addition to being the organs for respiration, a dragon’s breath weapon is generated in its lungs from secretions produced by the draconis fundamentum.” Considering that dragonborn have dragon ancestry, it would make sense that a dragonborn’s ability to breath fire is physiologically based as well, despite 5e’s lack of clarity in RAW. As always, though, it’s up to the DM to allow a breath weapon in Wild Shaped forms.