Green Anole

Quick Take

• The green anole is nicknamed the American chameleon, though calling it that reveals a common misunderstanding about what it actually is. See its true classification →
• When a rival invaded its territory, the green anole made a remarkable physical change to survive. Scientists caught it happening in real time. Meet the rival invader →
• Its color-changing ability is tied to a hormone, though the trigger isn't what most people assume. Discover the color-change trigger →
• Female green anoles have a reproductive trick that gives them unusual control over when their eggs get fertilized. Explore egg fertilization control →

The small lizard is native to the southeastern United States, found from Florida to central Texas, and has been introduced to some Caribbean islands such as Cuba and the Bahamas. It is an arboreal species that is related to the iguana. Although the green anole is often called the American chameleon due to its color-changing ability, it is not a true chameleon, which is not native to the United States. Other names are common green anole, American green anole, Carolina anole, and red-throated anole.

Incredible Green Anole Facts

• Its tail falls off when grabbed, and it later grows back.
• Like other lizards, it runs faster when startled or yelled at.
• It changes color due to melanophore-stimulating hormone (MSH).
• Color changing depends on temperature, humidity, mood, and health.
• It must be handled gingerly.

Evolution and Origins

The green anole, also known as carolinensis and sometimes mistakenly referred to as the American chameleon, originates from the southern regions of the United States.

Although it can exhibit color variations ranging from green to brown or spotted, its capability to change colors is relatively limited when compared to that of authentic chameleons found in the Old World.

Anolis lizards have their roots in mainland America, but they have successfully expanded their territory to the Greater Antillean islands and subsequently returned to the mainland, creating three distinct categories (Primary and Secondary Mainland and Greater Antillean) in the process.

Furthermore, through DNA sequencing, researchers have established that the green anole is related to larger lizards originating from Hispaniola.

Classification and Scientific Name

The green anole’s scientific name is Anolis carolinensis. Anolis is a genus of lizards in the Iguania suborder and the Anolidae family. It is part of the larger Reptilia class and Squamata order. The Iguania suborder includes color-changing species such as iguanas, chameleons, and agamids, along with New World lizards such as anoles and phrynosomatids.

Appearance

The green anole is a small to medium-sized lizard. It has a slender, agile body, a long, pointed head with ridges between the eyes and nostrils, smaller ridges on top of its head, and toe pads. The species is sexually dimorphic, with males being 15 percent larger and females being smaller in all body size measurements.

Males also have a dewlap (throat fan) that is larger than the female’s and is pink or reddish, whereas the female’s range from gray to white and are not a common feature. Males also have a dorsal ridge that they can extend behind the head while displaying or experiencing stress. Finally, males get scars on the head and face from fighting other males over territory or during the mating season. Females have a white stripe running along their spine, unlike most males.

Additionally, there are heavyweight and lightweight size classes or morphs of adult males, which can both exist within one population. These differ in dominance, bite force, body mass and length, competition, and vertical jump.

Color changing depends on the environment and health or mood. When it’s green, it’s active and in bright light. When it’s brown, it’s less energetic and in a cool or moist environment.

Behavior

The males puff out their dewlap, do push-ups, or bob their heads when intimidated by other males. They are territorial and will fight with other males by biting, scratching, or chasing them away. A male’s territory can range from as small as 1 cubic meter (35 cu feet) up to 50 to 100 square meters, and may overlap with the home ranges of 2 to 3 females. Due to male territorialism, lizard owners should keep males alone or house one male with a few females.

Green anoles are diurnal (active during the day) throughout the year. They are especially active during the spring and fall, while winter activity depends on the temperature and amount of sunlight. They are cold-blooded but heterothermic — meaning they can self-regulate their body temperature to some degree — yet still need supplemental heat for digestion and overall health.

Habitat

The typical habitat of green anoles is the moist forests and brushy clearings of Neotropical and Nearctic regions, including Georgia, South Carolina, and the southeastern United States. However, it has spread into the foliage of urban areas and the low-country shrubs of the Carolinas as well as to Hawaii, the Ogasawara Islands of Japan, Cuba, the Bahamas, and Guam.

Diet

Green anoles have a largely insectivorous, carnivorous diet consisting of mealworms, grubs, maggots, and small insects such as beetles, fruit flies, and termites. They also eat house flies in Georgia, South Carolina, and other southeastern urban areas, occasionally eat grains and seeds, and even other small lizards such as skinks. They only notice prey that is moving.

Predators and Threats

One of the uses for the green anole’s color-changing ability is to hide from predators by blending in with trees and bushes. Broadhead skinks, snakes, and birds are common predators, with cats being another in urban habitats. Although the green anole is threatened by over-predation, it is not endangered in general.

It did, however, go extinct on one island in the Bahamas due to the curly-tailed lizard, a ground-dwelling species that eats lizards and anoles. In Guam, predators such as brown tree snakes (scientific name Boiga irregularis) have reduced their population density.

The brown anole is an invasive species in the green anole’s native habitat and competes with it for shelter and food. As a result, the green anole evolved to live higher up in trees and grow bigger toe pads to be able to climb and run faster.

Reproduction and Life Cycle

Green anoles reach sexual maturity at 8 to 9 months. The mating season for green anoles is from April through August, or 4 to 5 months out of the year. During this time, males attract females with head-bobbing and extending their dewlaps. Females who are receptive to mating arch their necks. The male bites the neck of the female, a behavior unique to green anoles. He then places his tail under the female and mounts her back.

Reproduction rates peak during the warmer months, as heat increases gonad size. Males are territorial in order to protect their mating partners from intruding males, while females mate in sheltered areas and closed terrain to reduce exposure to predators.

Female green anoles can store sperm for delayed fertilization. The gestation period is 5 to 7 weeks, with the female laying one egg every two weeks for an average of 6 to 9 eggs a year. The eggs are buried in moist soil, which the female digs, and left to incubate and hatch on their own, meaning the young are left to fend for themselves.

Population

These anoles are the most commonly seen lizard in Alabama and the most common lizard in both urban and suburban areas in the southeastern United States. Florida used to contain the majority of green anoles, but they have been largely replaced by invasive anole species such as the brown anole (Anolis sagrei). On the other hand, the green anole is an introduced species in Hawaii, the Ogasawara Islands of Japan, Cuba, the Bahamas, and Guam. They are classified by the IUCN as Least Concern.