The Carolina anole (Anolis carolinensis) (US: Â (Â listen)) is an arboreal lizard found primarily in the southeastern United States and some Caribbean islands. Other common names include the American green anole, American anole, and red-throated anole. It is also sometimes referred to as the American chameleon due to its ability to change color from several brown hues to bright green, and its somewhat similar appearance and diet preferences. However it is not a true chameleon and the nickname is misleading.
Description
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The Carolina anole is a small to medium-sized lizard, with a slender body. 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. They exhibit sexual dimorphism, the males being fifteen percent larger. The male dewlap (throat fan) is three times the size of the female's and bright red, whereas that of the female is lighter in color, ranging from white to pale pink. Males can extend a pronounced dorsal ridge behind the head when displaying or when under stress. Females have a prominent white stripe running along their spine, a feature most males lack.
Adult males are usually 12.5â€"20.3 cm (4.9â€"8.0 in) long, with about 60-70% of which is made up of its tail, with a body length up to 7.5 cm (3.0 in) and can weigh from 3â€"7 g (0.11â€"0.25 oz).
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 iguanas 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.
The typical coloration for a green anole ranges from the richest and brightest of greens to the darkest of browns, 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 when the background is other than green and the anole changes color to camouflage itself. However, the color change is not simply a matter of matching the background: the anole changes its color depending on its temperature, mood, and level of stress. In bright sunlight, against foliage, it appears emerald in color, but in shadier, cool, or moist conditions, or when under stressful conditions such as a territorial confrontation with another anole, the animal may darken itself to a grey to olive brown color. 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 stressedâ€"while fighting, for exampleâ€"the skin immediately 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 rareâ€"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.
Taxonomy
Anolis carolinensis is a species of the large Anolis genus of lizards within the Dactyloidae family (anole lizards). Within the genus, thirteen species have been identified as a distinct clade, referred to as the Anolis carolinensis series of anoles. This group are mid-sized trunk crown anoles large, conspicuously elongated heads and extreme levels of sexual dimorphism. The species was named by Friedrich Siegmund Voigt (1781 - 1850) in 1832.
Two subspecies are accepted, Anolis carolinensis carolinensis and Anolis carolinensis seminolus, found in the northern and southern reaches of the species distribution respectively, and hence are also known as the northern and southern green anoles.
Distribution and habitat
This species is native to North America, where it is found mainly in the subtropical southeastern parts of the continent. Anoles are 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. They have been found as far north as northern Tennessee and southeastern Virginia. In the Carolinas they are found in the coastal plains and 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 Hawaii and the Ogasawara Islands. 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, but is also a common sight in urban areas on steps and railings, adjacent to foliage. It is common on roadsides, the edges of forests where there are shrubs and vines, but also building sites having abundant foliage and sunlight. Their preferred habitat is moist forests, and brushy clearings.
Conservation
Carolina-anole males that encounter rival males frequently find it is an introduced and invasive brown anole (Anolis sagrei, also known as the Bahaman anole). When browns first appeared in the United States in the early 1900s, the Carolinas ceded their ground-level territories and were relegated to a very different ecosystem high in the treetops. On occasion, a more aggressive Carolina anole may be seen closer to the ground and in competition with the brown anoles.
Currently A. carolinensis is abundant in its area of distribution, and is able to thrive in disturbed areas, so is not considered threatened, but the brown anole represents a developing threat in the future.
Behavior
Male anoles are strongly territorial creatures. Some have even been witnessed fighting their own reflections in mirrored glass. The male will fight other males to defend his territory. On sighting another male, the anole will compress his body, extend the dewlap, inflate a dorsal ridge, bob his head and attempt to chase the rival away. If the rival male continues to approach, anoles will fight by biting and scratching each other. Serious injury is rare, but males often carry numerous scars on their head and face, especially during the mating season. Their territory, which is about 1 m3 (35 cu ft), usually includes two to three females.
The Carolinian anole is diurnal and active throughout the year, peaking in spring and fall. Winter activity is dependent on sun and temperature.
Diet
An anole's diet consists primarily of small insects such as crickets, grasshoppers, spiders, flies and other arthropods. Although anoles have been observed preying upon smaller reptiles such as juvenile skinks, this is not thought to be typical behavior. Many people who keep these lizards as pets feed them mealworms, grubs, maggots, and small crickets.
Predators
Major predators include the broadhead skink, snakes, birds, and in urban habitats, cats. Like many lizards, anoles display autotomic tails, which wriggle when broken off. This distracts the predator and helps the anole to escape. A new tail then starts to develop. The new tail, however, containing cartilage rather than bone, will typically not grow back to the same length as the first one, and may exhibit a marked difference in color and texture from the rest of the animal.
Anoles are parasitized by some species of sarcophagid flies, including Lepidodexia blakeae. Adult flies will deposit eggs on live anoles, and the fly larvae develop inside the lizard until they emerge from a wound and pupate into adult flies in sediment. Infection is often fatal, with mortality rates possibly as high as 90%.
Reproduction
The typical breeding season for green anoles starts as early as April and ends in late September, gonadal activity being largely regulated by photoperiod, enlarging in spring as the weather warms up and days lengthen, and then regressing in late summer.
During this time, the males patrol their territory and the most brilliant displays of these creatures can be seen. Males defend their territory and females from rivals, while courting the females with elaborate displays of extending their brightly colored dewlaps while bobbing up and down, almost doing a dance. The dewlap is also used to ward off other males. The male courts and pursues a female until the two successfully mate. Usually, when the female is ready to mate, she may let the male catch her, at which point he will grasp her by biting a fold of her skin behind her neck. The male will then position his tail underneath the female's tail near her vent. Males have two sex organs, known as hemipenes, which are normally kept within the body but are everted from his vent for mating. Males seem to alternate between the left and right hemipenis on successive matings.
The female matures one ovarian follicle at a time, the ovaries alternating in production. The sight of a courting male induces ovarian development, sexual receptiveness and then ovulation. About two to four weeks following mating, the female lays her first clutch of eggs, usually one or two in the first clutch. She can produce an egg every two weeks during the breeding season, until about 10 eggs have been produced. However, she can store sperm for up to eight months following mating. She then buries the soft shelled eggs in a shallow depression in soft soil, leaf litter, compost, rotting wood or even a hole in a nearby tree. Eggs average 12.5Â mm (0.49Â in) by 9.3Â mm (0.37Â in) in size.
The eggs are left to incubate by the heat of the sun, and if successful, will hatch in about five to seven weeks (30â€"45 days) from late May to early October. On hatching, the hatchlings are 52â€"67 mm (2.0â€"2.6 in) in length.
The hatchlings must fend for themselves as they are not cared for by either parent. The young hatchlings must be wary of other adult anoles in the area, as well as larger reptiles and mammals, which could eat them. Younger anoles differ from adults in having less obvious head ridges, a wider head and shorter tail. They mature in about eight months.
Captivity
Green anoles' nervous natures makes it advisable not to attempt to handle them very often; despite this, green anoles are popular pets. Individual animals may or may not adapt readily to cage life. Care must be taken to ensure the animals receive the support they need to adapt to captivity and live full and enriching lives; choosing an adequately-sized enclosure as well as the appropriate plants and substrate material goes a long way in this regard.
Green anoles can live in a 20-gallon or larger terrarium, with numerous plants lining the back and sides of the cage. Leave an open area in the front center as an arena in which feeder insects, appropriately fortified with calcium supplements, can be dropped in clear view of the lizards. Green anoles like to leap down on potential prey and engulf it.
Although green anoles are not overly social animals, in the wild they do interact with their neighbors and form loose clans. This can be successfully translated into captive life with several females kept together in the same enclosure, although the more lizards are kept, the larger the tank must be. However, having more than one adult male in a tank will inevitably lead to territorial disputes and fighting regardless of the enclosure's size, resulting in increased stress for all the animals in the cage.
Provide a heat light over some of the highest plants so the reptiles can bask directly below it. In the wild, anoles drink by lapping water droplets off of leaves; thus, water is best administered with a mist bottle, as the lizards may ignore a water dish even after becoming severely dehydrated. As with all reptiles, it is important to keep the temperature and humidity of their environment within their comfort zones.
Genomics
This species has been chosen as a model reptile for genomics by the National Human Genome Research Institute genome sequencing program. It was selected because of the ease and low cost of laboratory breeding and evolutionary value of the diversity of the genus. In 2011, the complete genome of this lizard was sequenced and published in Nature. Before its genome was published, only mammals and three bird species had been sequenced among amniotes. The draft genome sequence is 1.78 Gb (compared with 2.0â€"3.6 Gb mammalian and 0.9â€"1.3 Gb avian genome assemblies), of which 27% are mobile elements such as LINEs. A total of 17,472 protein-coding genes and 2,924 RNA genes were predicted from the A. carolinensis genome assembly.
Gallery
References
External links
- Anole genome sequencing project at NCBI
- Carolina anole at the Encyclopedia of Life
- "Breeding green anoles (Anolis carolinensis) in captivity"
- Green anole care sheet
- View the Carolina anole genome in Ensembl.