The American Crocodile (Crocodylus acutus) is the only species of true crocodile found in the United States. Florida is the unique location globally where this species shares its habitat with the American Alligator, creating a specialized ecological overlap. The crocodile population is smaller and more restricted than the widespread alligator population. Understanding the current population size and how scientists monitor these reptiles provides insight into the health of South Florida’s delicate estuarine environments.
The Current Population Count and Conservation Status
The American Crocodile population in Florida represents a significant conservation success story, recovering from historical lows. By the mid-1970s, the number of non-hatchling crocodiles was estimated to be only between 100 and 400 individuals, a drastic decline driven by habitat loss and hunting. This critically low number prompted the U.S. Fish and Wildlife Service (USFWS) to list the American Crocodile as federally endangered in 1975.
Intensive management and protection efforts since that time have allowed the population to rebound substantially across its limited range. Current estimates suggest the Florida population has grown to include as many as 2,000 adult crocodiles, with some estimates ranging up to 3,000 individuals across all age classes. Due to this sustained increase, the USFWS officially downlisted the species from endangered to federally threatened in 2007. The species remains protected under the Endangered Species Act as it continues to face threats from habitat modification and human encroachment.
The Unique Florida Habitat and Range
The American Crocodile’s presence in Florida is limited to the extreme southern tip of the state, a distribution dictated by its requirement for warmer temperatures and brackish water. Unlike the American Alligator, the crocodile possesses specialized salt glands that allow it to tolerate high-salinity environments. This tolerance confines the species primarily to coastal, subtropical areas like mangrove swamps, estuarine creeks, and coves.
The core of the crocodile’s range is concentrated in the coastal areas of Miami-Dade, Monroe, and Collier counties, extending through the Florida Keys. Specific areas include the southern portions of Everglades National Park, Biscayne Bay, and the Crocodile Lake National Wildlife Refuge. The cooling canal system of the Florida Power & Light Company’s Turkey Point Power Plant has inadvertently become a significant nesting habitat for hundreds of crocodiles.
Telling Crocodiles and Alligators Apart
Distinguishing the American Crocodile from the American Alligator relies on three primary physical characteristics. The most notable difference is the shape of the snout, where the crocodile features a narrow, tapered, V-shaped muzzle. In contrast, the alligator’s snout is much broader and more rounded, taking on a characteristic U-shape.
The arrangement of teeth offers another clear distinction when the animal’s mouth is closed. The crocodile’s upper and lower jaws are nearly the same width, causing some lower teeth to be visible and interlock. The fourth tooth on the lower jaw is always exposed and fits into a notch in the upper jaw. The alligator has a wider upper jaw that completely conceals its lower teeth when its mouth is shut. American Crocodiles tend to be a lighter, grayish-green color, while American Alligators are typically darker, exhibiting a gray to nearly black coloration.
Methods Used to Monitor the Population
The population figures and conservation status determinations are derived from systematic monitoring efforts conducted by agencies like the FWC and USFWS. A common assessment method is the use of nocturnal spotlight surveys, where researchers travel by boat along coastal shorelines at night to count crocodiles by the reflection of their eyes. During these surveys, crocodiles are often captured, measured for length and mass, and marked in a formal capture-mark-recapture program.
This mark-recapture approach involves tagging individuals with unique identifiers, such as passive integrated transponder (PIT) tags or scute clippings (coded notches cut into the tail scales). Recapturing these marked animals allows biologists to calculate growth rates, survival rates, and estimate the overall population size. Additionally, annual nesting surveys are conducted to locate and monitor the number of nests, which serves as a reliable indicator for estimating the size of the breeding female population.