There should at least be animals not usually there. Depending on the heat levels there, there may be fire ants. Fire ants are migrating north thanks to global warming. Armadillos are also finding new territory north of their usual areas (aka, Mexico) Also, the New York zoo and Smithsonian zoo boast some exotic populations and breeding programs. Maybe some of them managed to take hold.
I remember on that "Life After People" documentary/what if all humans die show, the dog populations around the world mice with the wild wolf/coyote/fox populations as created new, medium to small sized canine breeds. That's seems extremely likely.
Cats as well created new breeds. With the seeds from groceries, new plants took root. Skyscrapers, with their ability to quickly turn into vertical greenhouses, became a new ecosystem similar to the ecosystems you see in rainforests. Each level had its own little population of plants, insects, birds (as I expect, lidgeons still thrive), and small predators like cats and dogs, and all are descended from the left-behind species. Of course, after five hundred years, nearly every skyscraper fell and those ecosystems were lost. But if some are still remaining, that seems like a likely side-effect of having so many exotic fruit and vedgetables in one area and not eating them all.
Of course, we can't forget the trademarked Glo-fish. The jellyfish gene for bioluminescence, taken and put into tetra fish and then sold as a cheap, easy to raise pet. Imagine taking that gene and putting it into other pets. Look, guys! My cat glows fluorescent pink! Ooooooh! We sell those fish at Wal-mart. It's quite the attraction for the less pet-friendly people who just want an interesting thing to look at.
Edit: just looked at the glofish website. Turns out they glow their fluorescent colors under natural and ultraviolet light. So, they glow all the time.













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