One of the most widely-distributed large mammals in North America, white-tailed deer (Odocoileus virginianus), can be found at Fire Island National Seashore. While native to the Northeastern United States and Atlantic barrier islands, deer were not numerous on Fire Island in 1964 when the park was established. Their numbers have increased dramatically since that time due to abundant food sources and a lack of natural predators.
Deer are prevalent across Fire Island: from the Fire Island communities on the western end of the island, to the undeveloped Otis Pike Fire Island High Dune Wilderness on the eastern end. Deer are also abundant at the William Floyd Estate, a unit of Fire Island National Seashore located on Long Island.