First about the shadows - The trees are taller than he so they are going to cast a longer shadow

Then about rotating the pictures - Again no expert but it seems in rotating the picture you are not going to see less distance between his hind legs in the picture where he is walking away from the person with the camera. And I don't think you would see less of his left antler nor the color difference of that same antler between the 2 pictures.

I'm still undecided at this point, but tend to believe it is real. I've never seen a moose up close, except mounted over a fireplace in a fancy bar/restaurant, so I really can't imagine how big thse things get even after reading the information you posted above.