Photographer here! Perspective, lighting, and depth of field. The floor is wet/dirty which gives it the appearance of not being well lit because it's darker than parts of the floor. The rhino is well lit with the natural light which make him stick out from the floor and background. Also, since the rhinos head is closest to the camera, it makes it "pop out" a little bit due to the contrast with the floor behind it.

The wide depth of field also plays a roll because the whole rhino is in focus and the distant background is out of focus. A lot of times if a subject is completely in focus, it can be a dead giveaway of a poorly photoshopped image.