I rode Highway 41 (south of Alligator Alley) along the northern edge of Everglades National Park in March.  There were numerous signs warning drivers (riders) of Panthers, and a few dead (road kill) alligators on the shoulder of the highway.  So I guess they can get under the fence if they want to.  Not a place I wanted to break down.  man those full grown Alligators are ugly!