Crocodile Lake National Wildlife Refuge covers 6,686 acres in north Key Largo, protecting one of only three remaining breeding populations of the American crocodile in the United States. The refuge was established in 1980 under the Endangered Species Act and is one of the reasons the American crocodile population has recovered from near-extinction; it also shelters the Key Largo woodrat, the Key Largo cotton mouse, and the Schaus swallowtail butterfly, all found nowhere else.
The refuge's natural areas are closed to the public to protect nesting habitat, but the refuge office distributes information and maintains a small butterfly garden beside the building. The American crocodile — larger and more salt-tolerant than the American alligator — is occasionally seen in the canals and mangrove channels of north Key Largo; they are shy and rarely approach people. Seeing one in the wild is a reminder that the Florida Keys, for all their tiki bars and dive shops, are still genuinely wild at the edges.