Since the Key Largo woodrat has a small and specific habitat, it is susceptible to human encroachment. Since the 1920s, it has lost almost half of its traditional habitat. In the early 1980s, biologists began equipping rats with radio devices to count them and study them; by the end of the 1980s, a study showed that the rat had disappeared from Key Largo proper and its total population had dwindled to some 6500 animals on North Key Largo. Its fate in Key Largo was tied to that of the American Crocodile, and when a planned reservation for the crocodile in North Key Largo bogged down during the presidential transition in the US Administration in 1980, the woodrat was threatened with extinction; the crocodile reservation was to be a haven for the woodrat, and also for the rare Schaus Swallowtail butterfly. A project called Port Bougainville, with 15 hotels besides condos, would add 45,000 inhabitants to North Key Largo by the year 2000, adding to the pressure on the crocodile and other animals.