The Lower Keys Rabbit is a marsh rabbit subspecies found only in the very southern tip of Florida. They live in coastal marshes, eat grass and tree bark, and are endangered because of habitat loss. There's only about 300 of the furry little things left. Like Key Deer, the Lower Keys Rabbits are smaller than their cousins. There are marsh rabbits all over the southeastern United States, but the theory is that when sea levels rose 10,000 years ago, some animals got stranded. The isolation and environmental differences led to the emergence of a new subspecies of marsh rabbit.
In the 1980s, biologist James Lazell was the first to show that the little marsh rabbits were a distinct subspecies. Presenting his research in the Journal of Mammology, he wrote: "In accord with the tradition of patronyms, the new form is named for Hugh M. Hefner, whose corporation has generously supported field work on this and other species." (Yes, that would be the Playboy Corporation.) The rabbit's official scientific name is Sylvilagus palustris hefneri.
Lower Keys Rabbit (pdf file, U.S. Fish and Wildlife Service)
James D. Lazell, Jr. A New Marsh Rabitt (Sylvilagus Palustris) from Florida's Lower Keys. Journal of Mammalogy, 1984, Volume 65, Number 1, pages 26 - 33.