Anolis carolinensis or green anole () (among other names below) is a tree-dwelling species of anole lizard native to the southeastern United States and introduced to islands in the Pacific and Caribbean. A small to medium-sized lizard, the green anole is a trunk-crown ecomorph and can change its color to several shades from brown to green.
Other names include the Carolina anole, Carolina green anole, American anole, American green anole, North American green anole and red-throated anole. It is commonly called chameleon in the southeastern United States and sometimes referred to as the American chameleon (typically in the pet trade) due to its color-changing ability; however, it is not a true chameleon.
Taxonomy Anolis carolinensis is a species of the large lizard genus Anolis within the family Dactyloidae (anole lizards). This species was named by Friedrich Siegmund Voigt (1781-1850) in 1832.
Phylogenetic evidence indicates that the Carolina anole belongs to the Anolis carolinensis anole series, a wider clade of Caribbean Anolis which are all also known as "green anoles". This group is composed of mid-sized trunk-crown anoles with large, conspicuously elongated heads and extreme levels of sexual dimorphism. Other members of this thirteen-species clade include A. brunneus & A. smaragdinus from the Bahamas, A. longiceps from Navassa Island, A. maynardii from the Cayman Islands, and A. allisoni & A. porcatus from Cuba; A. carolinensis is the only member of this clade native to the American mainland. Genetic analysis indicates that A. carolinensis originates from an oceanic dispersal event of an ancestral green anole from Cuba to the southern United States during the late Miocene or Pliocene. This is a rare example of an insular species successfully colonizing the mainland of a continent rather than the more common vice versa, although several other Caribbean animal and plant groups have similarly successfully colonized mainland North America via Florida. The present diversity of Central and South American anoles is also thought to originate from a colonization of the American mainland by an insular Caribbean anole taxon.
Description The anole is a small to medium-sized lizard, with a slender body. Males of this species are slightly larger than females. The head is long and pointed with ridges between the eyes and nostrils, and smaller ones on the top of the head. The toes have adhesive pads to facilitate climbing. Green anoles use jumping for their primary means of locomotion. They exhibit sexual dimorphism, the males being fifteen percent larger. Adult males within a population can be classified within a heavyweight and a lightweight morph. The male dewlap (throat fan) is three times the size of the female's and bright orange to red, whereas that of the female is lighter in color. The dewlap is usually pink for Anolis carolinensis (more orange-red in A. sagrei) and is very rarely present in females. The color of the dewlap is variable and different from the lizard eye to the human eye. Green anoles are thought to be capable of seeing a larger range of the UV spectrum, and that the dewlap reflects ultraviolet light to attract mates. Female anoles do, however, often have a dorsal line down their back. Extension of the dewlap from the throat is used for communication. Males can form a pronounced dorsal ridge behind the head when displaying or when under stress. Females and juveniles have a prominent white stripe running along their spine, a feature most males lack.
Adult males are usually long, with about 60-70% of which is made up of its tail. They have a body length, also known as a snout to vent length (SVL), up to and can weigh from .John B. Jensen. Amphibians and Reptiles of Georgia. University of Georgia Press, 2008. Green Anole p. 296. Savannah River Ecology LaboratoryAnimal Diversity Web, p. 1Animal Diversity Web, p. 2
Coloration and color morphs
Colour varies from brown to green and can be changed like many other kinds of lizards, but anoles are closely related to iguanasNCBI Taxonomy Browser and are not true chameleons. Although A. carolinensis is sometimes called an 'American chameleon', true chameleons do not naturally occur in the Americas, and A. carolinensis is not the only lizard currently in its area of distribution capable of changing colour. In contrast, many species of true chameleons display a greater range of color adaptation, though some can hardly change color at all.Amphibians and Reptiles of the Carolinas and Virginia. Bernard S. Martof, Julian R. Harrison, III, William M. Palmer, Joseph R. Bailey. University of North Carolina Press, 1989.
Typical coloration for a green anole ranges from bright green to dark brown, with little variation in between. The color spectrum is a result of three layers of pigment cells or chromatophores: the xanthophores, responsible for the yellow pigmentation; cyanophores, responsible for the blue pigmentation, and melanophores, responsible for the brown and black pigmentation. The anole changes its color depending on mood, level of stress, activity level and as a social signal (for example, displaying dominance). Anolis carolinensis takes darker coloration as its base color at the beginning of the breeding season when it is generally cooler, and the adult males change their body coloration to more greenish when they need to advertise their territorial possession. Although often claimed, evidence does not support that they do it in response to the color of the background (camouflage). Whether they do it in response to temperature (thermoregulation) is less clear, with studies both supporting it and contradicting it. Changing color while under a sharply contrasting shadow can cause a "stencil effect", where the outline of the shadow is temporarily imprinted in the animal's coloration (see image in gallery, below). When stressed—while fighting, for example—the skin just behind the lizard's eyes may turn black independently from the rest of the animal's coloration, forming "postocular spots".
A lack in one of the pigment genes causes color exceptions. These color mutations are also called phases. The rare blue-phased green anole lacks xanthophores, which results in a blue, rather than red, often pastel blue, anole. These specimens have become popular recently in the pet trade market. When the anole is completely lacking xanthophores, it is said to be axanthic and the animal will have a completely pastel- or baby-blue hue. They are extremely rare—usually produced in one of every 20,000 individual anoles in the wild. Another phase is the yellow-phased green anole, which lacks cyanophores. Colonies of these rare color-phased anoles have been reported, but anoles with these color mutations rarely live for long, since the green color provides camouflage for hunting down prey, as well as hiding from predators.
Distribution and habitat
This species is native to North America, where it is found mainly in the subtropical southeastern parts of the continent. They also inhabit grasslands, forests, and temperate zones. Anoles are the most abundant on the Atlantic Coastal Plains in North Carolina, South Carolina, Georgia and Florida, and on the Gulf Coast in Alabama, Mississippi, Louisiana, and Texas, where they extend inland as far as Texas Hill Country and the DFW Metroplex; they have also been recorded in Tamaulipas, Mexico, but it is mostly likely an introduction. In the Carolinas, they are found on the coastal plains as far north as False Cape in Virginia, and in the southern piedmont of North Carolina, but throughout South Carolina, while in Georgia they are widespread except in the Blue Ridge region.
The species has been introduced into various locales in the Pacific and the Caribbean: Hawaii, the Ogasawara Islands, the Northern Mariana Islands, the Bahamas, Anguilla, Palau, and Saint Vincent and the Grenadines, as well as the Canary Islands. In 2005 they were recognized and listed as an invasive alien species in the Ogasawara Islands of Japan for causing insect population collapse.Toda, M., Takahashi, H., Nakagawa, N., Sukigara, N. (2010). Ecology and Control of the Green Anole (Anolis carolinensis), an Invasive Alien Species on the Ogasawara Islands. In: Kawakami, K., Okochi, I. (eds) Restoring the Oceanic Island Ecosystem. Springer, Tokyo. . Green anoles have also been considered successful invaders as they have made their way into parts of Europe. They have been sighted in Orange County and San Diego County of southern California, with sightings in San Diego going at least as far back as 1993.
A. carolinensis is arboreal in nature but may be seen on the ground and frequently seen on shrubs in the low country of the Carolinas. However, it can live in cities like Atlanta with little trouble so long as there is plentiful vegetation and bugs to eat. Compared to other species of lizards, green anoles are known to be the ones with the most adaptation to human encroachment. One can observe them on steps, trellises, and railings adjacent to foliage; on particularly hot summer days they may seek to cool off on indoor walls or on wrap around porches of older buildings, and in the former case can simply be captured in a shoebox and gently placed outdoors. It is common on roadsides, the edges of forests where there are shrubs and vines, but also construction sites having abundant foliage and sunlight. Their preferred habitat is open pine communities with a greater shrub density, it may harbor a greater abundance of anoles where they are able to watch for prey and intruders coming into their territory.
Conservation
Although not threatened as a species, Carolina anoles increasingly struggle with competition from introduced anole species, such as the brown anole (Anolis sagrei), also known as the Bahamian anole. This competition happened to be an interesting model for evolutionary studies, as it illustrates the process of adaptation. When A. sagrei first appeared in the United States in the early 1900s, the Carolina anole mostly ceded ground-level territories and were relegated to a very different ecosystem high in the treetops. On occasion, more aggressive Carolina anole individuals may still be seen closer to the ground. Currently, A. carolinensis is abundant in its area of distribution and is able to thrive in disturbed areas, so it is not considered threatened, but A. sagrei may represent a developing threat in some areas.
Relationships and hybridization
A. carolinensis has been found to regularly hybridize with a closely related species, Anolis porcatus (the Cuban green anole), in Southern Florida, where A. porcatus has been introduced. A 2022 study found there to be asymmetric introgression of certain A. porcatus alleles within the population of hybrid individuals, three of which were found to be significantly associated with environmental variables indicative of urbanization. It remains uncertain as to how this admixture of invasive alleles to the Carolina anole will affect the conservation of the species going forward. Not all admixture from invasive populations should be viewed as a negative outcome, and adaptive introgression as a result of hybridization with an ecologically robust invasive population might facilitate the long-term survival of native populations otherwise unable to adapt to human impact on the environment.
Behavior