We don’t have much in the way of sidewalks where I live, but carcasses appear on the side of the road quite frequently - birds, mongooses, feral pigs, feral kittens, toads. I am impressed by the speed with which they disappear, and have no idea where they’re going.
Well, except for the pigs: they probably get tossed in the back of the next passing pick-up truck and butchered. (I was once given a couple of kilos of roadkill pork when a friend’s boyfriend, a skilled hunter and butcher, found a dying pig on the road. It made a truly delicious vindaloo.)