Doesn't seem to be clearly defined. I'm expecting just Common +Int.
No languages at all? Or just:
"Growl once for Yes, Whine twice for No" ?
:<
Huh. Didn't even notice that.
The SRD claims "Skinwalkers are well attuned to the natural order of things..." My ruling as a GM would be common and sylvan seeing as that seems to be the language of forest creatures. (I admit I could be wrong on that.)
I might even give them an ability to speak with animals of its kind while transformed and rework the spell-like abilities of the variant heritages that already let you do that. It's not like Skinwalkers are all that powerful anyway and I think it makes sense given the fluff.