The Brown Anole (Anolis sagrei) is not native to Florida. It is one of the most common lizards encountered across the state, yet it is an established and highly successful invasive species. This small lizard is now the dominant anole species in many urban and suburban environments throughout the peninsula. Its presence has fundamentally altered the ecological dynamics for the native lizard populations in Florida.
Nativity Status and Origin
The Brown Anole is native to islands in the Caribbean, including Cuba, the Bahamas, and the Cayman Islands. The species first arrived in the United States accidentally, likely as stowaways on cargo ships carrying plants or other goods. The earliest documented introduction in Florida occurred in Key West during the late 1800s, with multiple introductions following in the Key West and Miami areas throughout the early 20th century.
Genetic analyses suggest that Brown Anoles were introduced to Florida at least eight different times from various Caribbean locations. The species’ high adaptability allowed it to quickly establish breeding populations. From these initial coastal footholds, the Brown Anole rapidly spread across the entire Florida peninsula, utilizing human transport pathways like vehicles and ornamental plant shipments.
Distinguishing Features
Differentiating the invasive Brown Anole from the native Green Anole (Anolis carolinensis) relies on specific physical traits, primarily color and pattern. The Brown Anole can change its shade from light tan to dark brown or gray, but it is never able to turn bright green. These lizards often display a distinct pattern, such as darker markings, spots, or a faint mid-dorsal stripe running down the back.
The native Green Anole is usually a uniform bright green when relaxed, but it can change its color to brown when stressed or cool. The dewlap, the expandable throat fan displayed by males, is another distinguishing feature. The Brown Anole’s dewlap is typically orange or red-orange, while the Green Anole displays a pink or red dewlap. Brown Anoles also tend to have a shorter, stouter head shape compared to the Green Anole’s more elongated snout.
Ecological Relationship with the Green Anole
The introduction of the Brown Anole has led to significant competitive displacement of the native Green Anole in Florida. Brown Anoles are generally more aggressive and are classified as “trunk-ground” ecomorphs. They naturally prefer lower perches on tree trunks, fences, and the ground. This preference puts them in direct conflict with the native species, which historically occupied these habitats.
When the two species co-occur, the Green Anole is forced to shift its ecological niche to avoid the dominant invader. Studies show that where Brown Anoles are present, Green Anoles move significantly higher into the canopy, sometimes perching up to 17 times higher than usual. This shift results in reduced access to food resources and preferred basking sites. Adult Brown Anoles are also documented predators of the native species’ young, consuming juvenile Green Anoles.
Habitat and Behavior in Florida
The Brown Anole’s success in Florida is attributed to its generalized habitat requirements and tolerance for human-altered landscapes. They are commonly found in urban and suburban environments, thriving on chain-link fences, low shrubs, garden beds, and the sides of buildings. This adaptability allows them to form dense populations in areas heavily modified by human activity, such as residential yards and commercial parking lots.
The diet of the Brown Anole primarily consists of insects, spiders, and other small invertebrates. Females reproduce frequently throughout the warm seasons, laying a single egg roughly every four to six days in moist soil or under debris. Males are highly territorial and constantly perform head-bobbing displays and extend their orange dewlap to assert dominance.