Kimber said in
rec.pets.dogs.behavior:

I've always thought a "normal" dog would cry and scratch at
the door, which is not at all subtle. It seems strange to
me that not all dogs instinctively do that.

What in a dog's heritage would instill an instinct to cry and
scratch as a signal to go outside?

Personally, I can think of a ton of indicators that I'd prefer
to crying and scratching.

--
--Matt. Rocky's a Dog.