I remember playing with dead animals, or at least poking them with sticks. Unless you are a kid with the habit of capture-and-torture, these are one of the few times you can use satisfy your curiosity without fear of any unpredictable reactions (biting you or thrashing aound-- both are frightening).
Examining usually elusive reptiles up close, seeing how stray cats' hair have a multitude of different colors but form an illusion of a singular muddy hue... These are the privileges of an observant child.
Furthermore, I firmly believe that seeing dead animals is important to a child's understanding of life and death.