The Florida Keys have their very own species of deer that exists only there: the Key Deer, Odocoileus virginianus clavium, originally roamed all of the lower Florida Keys but is now limited to a stretch from about Sugarloaf Key to Bahia Honda Key. How did they get here in the first place? Well, deer can swim, but it's been surmised by scientific sorts that they got here over a land bridge that must have existed towards the end of Wisconsin Glaciation period, roughly 10,000 years ago.
The earliest known written reference to Key Deer comes from the diary of Hernando de Escalante Fontaneda, a Spanish sailor shipwrecked at the age of 13 in the Florida Keys in the 1550s. The Calusa captured and enslaved the ship's crew, eventually killing them all except for Fontaneda. He spent the next seventeen years living among them, learning several native American languages in the process and traveling extensively through Florida. In 1566 he was rescued by Pedro Menéndez de Avilés, Florida's first Spanish governor and founder of St. Augustine.
Estimates of Key Deer population are put as high as 800 nowadays, a far cry from the days when they numbered in the tens of thousands but certainly a step up from 1955 when it was feared that only as few as 25 specimens existed.