Unknown tree frog

[dbolack]

Hello,

this (tree)frog has been found in a garden in Burgenland, eastern part of Austria. The only native treefrog there is Hyla arborea.
Does anybody of you have an idea, what it might be?

Any possibility that little fellow has been exposed to some chemicals? I've heard of people trying to bleach out tadpoles in swimming pols ending up with albino frogs. The near perfect circular bits make me wonder if he's be hit with some kind of pesticide or fertilizer granule, perhaps while hibernating?