It would seem that the size of the expansion cracks in the substructure of the bridge are just right for roosting Mexican free-tailed bats (Tadarida brasiliensis). And so the bats moved in, and in some big numbers. Bat Conservation International, based in Austin, estimates that there are between 750,000 and 1.5 million bats under the bridge in the summers (the bats migrate south for the winter).
And in a major success story for the conservation of bats, the bridge has become a tourist site and attracts hundreds of visitors every evening to watch the bats fly out. So instead of trying to get rid of the bats, Austin has all but adopted them. Even their hockey team is called the Austin Ice Bats.
So while this is arguably a "bat coin" it is a real coin with a bat on it and a neat story behind the location so I am putting it up there. This is a 199X Lincoln cent that was put into a souvenir machine that flattens out the coin and leaves a raised logo for the site. These are common at many tourist stops, but this is a cool one as it is for a bridge full of bats.