The Green Anole (Anolis carolinensis) is a small lizard commonly found throughout the southeastern United States, including Florida. Despite public confusion, the Green Anole is not an invasive species; it is native to the region. The confusion stems from the presence of another lizard that has profoundly altered the local ecosystem through intense competition for habitat and resources.
Florida’s Native Anole
The Green Anole is historically the only native anole species in the United States, with its range extending across the Southeast. This lizard is distinctly arboreal, preferring to live in trees, shrubs, and higher vegetation. Its body is slender, featuring a long, pointed head and large adhesive toe pads that allow it to climb vertical surfaces with ease. The species is well-known for its ability to change color, shifting from bright emerald green to various shades of brown or gray. This change is not for camouflage, as often believed, but is primarily a response to temperature, mood, or stress levels. Male Green Anoles possess a vibrant pink or reddish dewlap, a flap of skin under the throat, which they display during territorial disputes or courtship rituals.
The Real Invasive Species
The source of the invasive species confusion is the Brown Anole (Anolis sagrei), an aggressive non-native lizard. This species is native to Cuba, the Bahamas, and the Cayman Islands. It first arrived in Florida as early as the late 1800s, likely introduced accidentally as stowaways in cargo shipments from the Caribbean. The Brown Anole is classified as invasive because of its rapid reproduction rate, broad diet, and ability to thrive in high population densities. Females can lay one egg about every week during the breeding season, leading to swift population growth. This species is highly adaptable and quickly establishes itself in disturbed and urban environments across the state. Once established, the Brown Anole outcompetes and often preys upon the hatchlings of the native Green Anole. Its dominance at ground level and in low vegetation has resulted in the displacement of the native lizard from its preferred habitats.
Practical Guide to Identification
Distinguishing the native Green Anole from the invasive Brown Anole requires close observation of several physical characteristics. The most obvious difference is the color range: the Brown Anole is typically a solid brown or gray and cannot turn green. Conversely, the native Green Anole can be bright green, but it sometimes switches to a dark brown, which can cause misidentification. A reliable indicator is the color of the male’s dewlap, the throat fan used for display. The native Green Anole displays a distinctly pink or reddish dewlap, while the Brown Anole’s is typically orange or yellowish, sometimes with a white border. The Brown Anole also often features a pattern of light spots, triangles, or chevrons running down its back, a pattern usually absent on the native species. The native Green Anole has a more slender body and a long, pointed snout. In contrast, the invasive Brown Anole possesses a stockier body and a blunter, shorter head shape.
Ecological Shift and Competition
The invasion of the Brown Anole has triggered niche partitioning in the native Green Anole population. This process describes how species divide limited resources, such as physical habitat space, to minimize direct competition. The aggressive nature and higher population density of the Brown Anole have forced the native Green Anole to abandon its former range on the ground and lower tree trunks. The Green Anole has subsequently shifted its habitat use upward, now occupying a niche higher in the tree canopy on thinner branches and leaves. This change in vertical positioning reduces direct interference competition, which is often asymmetric in favor of the larger, more robust Brown Anole. This habitat displacement has led to significant evolutionary pressure on the native species. Over a relatively short period, Green Anoles in areas with Brown Anoles have evolved larger toe pads, or lamellae, on their feet. These larger pads provide a better grip on the smooth, narrow surfaces of the higher branches, demonstrating a rapid morphological adaptation to their new, elevated environment.