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Anolis carolinensisGreen anole

By Chelsea Crawford

Geographic Range

Anolis carolinensis (green anoles) is native to neotropical and nearctic regions. Anolis carolinensis occurs throughout much of the southeastern United States, extending north through parts of North Carolina, west to Texas, and south through Florida. While Florida was once the central portion of its United States distribution, today most Florida populations have been replaced by introduced anole species, such as Anolis sagrei.

In other parts of its geographic range, A. carolinensis is considered an introduced species. It has become abundant in Hawaii since it was discovered in 1950. It also has been introduced and has flourished in the Ogasawara Islands of Japan, and in Cuba, the Bahamas, and Guam. In Guam, however, densities have been impacted drastically by predators, such as introduced brown tree snakes (Boiga irregularis). (Bishop and Echternacht, 2004; Losos, 2009; Macedonia, et al., 2003; Mattison, 1989)

Habitat

Anolis carolinensis is a primarily arboreal lizard. Within natural habitats, A. carolinensis is found most often on shaded tree branches. Its positioning within a tree is known as its perch height and is dependent on the proximity of both predators and prey. Limited research has been done on their preferred types or species of trees. Anolis carolinensis appears mostly to inhabit trees and shrubs within their territory and where prey is readily available. They also are frequently observed in tall grasses.

Anolis carolinensis also is one of the most common lizards in urban and suburban areas. It is frequently found near dwellings, particularly on fence posts and the sides of buildings. (Mattison, 1989)

  • Range elevation
    45.73 to 609.76 m
    150.03 to 2000.52 ft
  • Average elevation
    327.75 m
    1075.30 ft

Physical Description

Anolis carolinensis varies in length from 4 to 8 cm. Females typically are smaller in all body size measures, at birth ranging from about 23 to 25 mm long. Both males and females have long tails that account for more than half of their total body lengths. Adult anoles weigh between 2 and 6 g.

Scale colors in green anoles vary. In most cases, these lizards range from shades of brown to green or gray. At times their coloring represents combinations of these colors. Color variation results from layers of pigmented cells called chromatophores. Three types of pigment cells are present: xanthophores, cyanophores, and melanophores, each responsible for different color variations. Green anoles are capable of changing scale color in response to their external environment. Many factors affect color change and variation; most often it is dependent upon temperature and excitation, such as increased activity or competition. Darker brown and black colors, produced by melanophores, typically signal cold or stressed conditions.

Within a population, two different size classes or morphs of adult males may be present: heavyweights and lightweights. These morphs differ in many ways, including bite force, body mass and length, competition, and vertical jump. The heavyweight morph is larger and more dominant. Some authors consider these morphs to be different developmental stages or different age classes among sexually mature males.

Physical differences also are common between males and females. Females often have a line that runs along their dorsal surface, from their neck down to their back, ending before their tail begins. Most males have dewlaps that extend from the ventral side (underneath) of their neck. Dewlaps are rarely seen in females. The dewlap is commonly pinkish in color and thought to be used by males to increase visibility as they court females. Displaying the dewlap may also represent a competitive status between males; in these cases, dewlap displays are usually related to territory boundary disputes. Subspecies Anolis carolinensis seminolus, abundant in southwest Florida, is physically very similar to A. carolinensis carolinensis, but its dewlap is often white or gray. (Bartlett and Bartlett, 2009; Crews and Greenberg, 1981; Lailvaux, et al., 2012; Smith, 1946)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • ornamentation
  • Range mass
    2 to 6 g
    0.07 to 0.21 oz
  • Range length
    10.16 to 20.32 cm
    4.00 to 8.00 in

Development

After a female lays her eggs, a five to seven week gestation period is necessary. Green anoles have genotypic sex determination. Once the young hatch from their eggs they resemble adults in coloration and pattern, but are only 23 to 25 mm long. Green anoles have determinate growth; they grow at a relatively constant rate from hatching to adulthood. Hatchlings develop into juvenile males and females without any parental investment. Juvenile males and females have the same resource and survival needs while developing, but competition among juveniles is generally low because resources tend to be plentiful. Since juveniles are not sexually mature, their main activities are associated with foraging, protection against predators, and maintaining adequate body temperatures. Initially, juvenile male and females do not show any sexual differences or display behaviors; however, during later stages of development, testosterone levels become higher in males and are likely to exhibit more aggressive behaviors.

Unlike other Anolis species, such as Anolis aeneus, green anoles do not leave their hatch sites after breeding. (Losos, 2009; Lovern and Jenssen, 2001; Oliver, 1951)

Reproduction

The majority of green anoles are polygynous. Especially in larger populations, they usually will mate only within their own territories. Females are not characteristically known to search for different mates. In cases when a female mates with a different male, it is usually due to intrusion into her territory.

Green anoles breed roughly four to five months out of the year, usually from April through August. Warmer months have the highest reproduction rate, because higher temperatures increase the size of male and female sexual structures (testes and ovaries). Ovulation cycle for female green anoles lasts approximately two weeks, which creates the intervals in which they mate.

The sexual display behavior of green anoles is very specific. Members of almost every mating pair live within each others territory. To attract the attention of females, males bob their heads up and down and extend their dewlaps. Not all females are receptive to male courtship; some deny them and others exhibit the same behavior as males but then arch their neck to inform the males they are receptive to mating. The male then approaches the female and bites the back of her neck, a distinctive behavior of green anoles. The male stabilizes himself by positioning his tail beneath the female’s body and then mounts her back. The male’s himepenes are at the base of his tail. Once in position, he will insert these into the female’s cloaca. Mating typically lasts only a few minutes.

Males protect their mating partners from other intruding males by defending their territory. At times, males have been found to deny receptive females due to their focus on territorial protection. Females also show protective behavior by mating primarily in sheltered areas and closed terrain, reducing vulnerability to predators. Unlike other Anolis species, such as Anolis aeneus, green anoles do not leave their hatch sites after breeding. (Losos, 2009; Ruby, 1984; Smith, 1946)

Breeding period for A. carolinensis occurs during warmer months, generally April through August. The breeding intervals are based on the female reproductive cycle, as they are only receptive to mating during their ovulatory cycle. The male is the main initiator of reproductive interactions and presents a strong display of attraction. This typically promotes a reproductive state in the female, similar to that of Anolis aeneus. Depending on how many ovulatory cycles a female has within a breeding season, she will lay six to nine eggs in a year. On average, she will lay a one to two egg clutch every two weeks. The male’s opportunities for mating correlates with the number of ovulation cycles a female has and the total number of potential mates within his territory range.

Two types of sexual selection occur during the mating season: intersexual and intrasexual selection. The larger a territory range a male has, the more females he is likely to mate with. A territory size usually relates to a male green anoles body size; the larger he is the more dominant he will be towards intruders and predators as he protects his territory.

Female green anoles have the ability to store sperm; this may be a trait of intersexual selection. Sperm has been found within a female seven months after mating, which may make delayed fertilization possible. Prior to releasing her clutch, the female will examine an appropriate area and then dig into the soil. Females prefer to release their eggs into moist soil. Eggs are oval and on average 6 by 4.5 mm. The gestation period varies, but is approximately five to seven weeks long. Hatchling anoles weigh 0.27 g each. Juvenile anoles are sexually mature at 8 to 9 months old. (Losos, 2009; Lovern, 2000; Ruby, 1984; Smith, 1946)

  • Breeding interval
    Green anoles breed in two week intervals throughout the spring to summer months.
  • Breeding season
    Green anoles breed 4 to 5 months out of the year, usually April through August.
  • Range number of offspring
    6 to 9
  • Range gestation period
    5 to 7 weeks
  • Range age at sexual or reproductive maturity (female)
    8 to 9 months
  • Range age at sexual or reproductive maturity (male)
    8 to 9 months

After ovulation, fertilization, and egg laying, no parental investment is known to occur. (Losos, 2009; Orrell, et al., 2004)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

Green anoles have a lifespan ranging from 2 to 8 years, determined largely by predation. Lifespan in captivity is similar to that in the wild, approximately 4 to 6 years, and dependent on proper care and conditions. Longevity also is greatly dependent upon proper nutrition. Smaller, slower, green anoles potentially have greater difficulty obtaining necessary nutrients than larger individuals, especially if engaged in competition. Larger green anoles under ideal natural conditions have been known to live up to 10 years. (Dirickson, 1976; Losos, 2009)

  • Range lifespan
    Status: wild
    <1 to 10 years
  • Average lifespan
    Status: wild
    5.5 years
  • Range lifespan
    Status: captivity
    1.5 to 7 years
  • Typical lifespan
    Status: wild
    2 to 8 years
  • Typical lifespan
    Status: captivity
    2 to 7 years

Behavior

Green anoles are a diurnal species. In both males and females, the majority of the day is dedicated to foraging. Prey capture somewhat distinguishes green anoles from related species, as they use a multitude of resources to capture prey. Green anoles move freely and range widely, but usually only within their territorial domains. In most cases, green anoles are positioned at a particular perch height, which is determined in a variety of ways, including the search for prey. Behavior changes slightly during the breeding season, when males dedicate more time to social interactions such as courting females. (Jenssen and Nunez, 1998; Losos, 2009; Orrell, et al., 2004)

  • Range territory size
    50 to 100 m^2

Home Range

Male territory size is directly correlated with its body size. The larger the lizard, the more territory he is able to patrol and protect. Female territories are much smaller, less than half of that of a male, and generally within the male’s home range. Even though males have much larger territory ranges than females, they spend the majority of their time within a specified female’s territory. Year to year, males tend to remain within the same territorial boundaries. Territory sizes vary, but on average range from 50 to 100 square meters. (Jenssen and Nunez, 1998; Losos, 2009; Orrell, et al., 2004)

Communication and Perception

Anolis carolinensis is equipped with certain communication signals from birth. Most communication involves color variations, actions such as head bobbing or neck biting, or use of the dewlap. The dewlap is used for inter-gender communication, especially during the breeding season. Displaying the dewlap also may be used to determine competitive status between males; in these cases, dewlap displays are usually related to territorial boundary disputes. Head bobbing or courtship bobbing is performed by both males and females to communicate breeding status, but is also done while in a threatened state.

Green anoles that have not yet reached adulthood do display adult signals and behaviors (e.g. head bobbing). However, since they are not sexually mature, these do not function as courtship mechanisms. Interactions between juveniles are similar to those of adult females. They generally are not as serious as those between adult males and usually do not result in injuries. As juveniles mature, their interactions often become more intense. This is mainly due to the development of structural hierarchies for adulthood. (Miller and Wolbarsht, 1962; Milstead, 1965)

Food Habits

Green anoles feed on a broad range of prey items. They often will attempt to eat anything smaller than their own head. They are classified as insectivores, eating a wide variety of insects, including beetles and flies, as well as spiders, some arthropods. At times, they also will eat mollusks, grain, and seeds. The importance of a particular prey or food item largely reflects its availability. If an item is abundant within the territory, green anoles are likely to feed on it more frequently.

Green anoles have several methods of capturing prey. Over 58% of the prey is captured by perching and watching or anticipating prey until they are within striking distance. This is considered to be the most effective means of capturing prey. This behavior is predominant during breeding, to conserve energy for mating. Another method of prey capture is used while the anole is protecting and patrolling their territory. In this case, they leap forward to ensure a capture, but use a slower motion. Another common method of prey capture is the ambush, usually used in capturing larger prey items. (Aborn and Froehlich, 1995; Losos, 2009)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • Plant Foods
  • seeds, grains, and nuts

Predation

Green anoles are preyed upon by a relatively large assortment of predators. Their main predators are snakes and birds, but they also are preyed on by larger reptiles. Brown tree snakes (Boiga irregularis) are particularly common snake predators. This species has eliminated green anoles from portions of Guam. Examples of birds that regularly prey on green anoles are American kestrels (Falco sparverius), pearly-eyed thrashers (Margarops fuscaturs), and lizard cuckoos (Saurothera vieilloti). A larger reptile that preys on green anoles is the curly tailed lizard (Leiocephalus carinatus). Other common predators, particularly in suburban areas, are cats, dogs, and frogs.

To avoid predators, green anoles hide in trees, tall grasses, and other vegetation. They also have developed a structure similar to a patagium that enables them to glide down from tall trees. In addition, green anoles have the ability to walk vertically on surfaces such as trees, walls, and fences using adhesive pads on the bottom of their feet. These provide a means of escape that the majority of their predators do not have.

Green anoles also utilize caudal autotomy and use their dropped tails to distract predators while they escape. (Lailvaux, et al., 2012; Losos, 2009; Lovern and Jenssen, 2001; Oliver, 1951)

Ecosystem Roles

Anolis carolinensis does not have a large ecosystem impact in most geographical ranges. However, their introduction in the Ogasawara Islands of Japan, however, has led to the decline of or extinction of many species, such as the Ogasawara tumbling flower beetle (Glipa ogasawarensis). In other regions, its greatest impact is as a prey species. For example, in Guam, green anoles are so heavily preyed upon by brown tree snakes (Boiga irregularis) that they have been nearly extirpated from the area.

Because A. carolinensis is highly territorial, especially the males, they may prevent certain other species from entering their territory. This potentially prevents certain reproductive variation. A beneficial quality of green anoles is that they consume seeds and grains, potentially aiding in seed dispersal. (Losos, 2009; Lovern and Jenssen, 2001)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

One of the best known positive economic factors involving green anoles are their presence in the pet trade. Green anole are sold in many pet stores in the United States. They also are exported for profit. In addition, lizards collected within the United States are sold to zoos and for educational programs. Green anoles also have been studied to better understand animal behavior.

Green anoles also are sometimes considered beneficial pest controllers, because they feed on pest species such as spiders, moths, and crickets. (Bartlett and Bartlett, 2009; Losos, 2009; Rohrilich and Rubin, 1975)

  • Positive Impacts
  • pet trade
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Anolis carolinensis on humans. Anolis carolinensis is a relatively harmless reptile. It is not aggressive toward humans, and its bite force is most likely insufficient to damage human skin. (Losos, 2009)

Conservation Status

Anolis carolinensis is currently considered to be at lower risk or of least concern and is not vulnerable to any major threats at this time. Some researchers believe that they may be at risk due to the significant numbers in the pet trade. However, in recent years, sales of green anoles have declined due to lesser demand. Also, green anoles appear abundant in the portions of their range from which they are collected and many populations occur in protected areas, such as parks and natural areas, which helps to protect the population. (Losos, 2009)

Contributors

Chelsea Crawford (author), Radford University, Christine Small (editor), Radford University, Rachelle Sterling (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

arboreal

Referring to an animal that lives in trees; tree-climbing.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

diurnal
  1. active during the day, 2. lasting for one day.
forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Aborn, D., D. Froehlich. 1995. An observation of a summer tanager attempting to eat an anolis lizard. Journal of Field Ornithology, 66/4: 501-502.

Bartlett, R., P. Bartlett. 2009. Guide and Reference to the Crocodilians, Turtles, and Lizards of Eastern and Central North America (North of Mexico). Gainsville, FL: University Press of Florida.

Bishop, D., A. Echternacht. 2004. Emergence behavior and movements of winter-aggregated green anoles Anolis carolinensis and the thermal characteristics of their crevices in Tennessee. Herptologica, 60/2: 168-177.

Crews, D. 1975. Inter- and intraindividual variation in display patterns in the lizard, Anolis carolinensis. Herpetologica, 31/1: 37-47.

Crews, D., N. Greenberg. 1981. Function and causation of social signals in lizards. American Zoologist, 21/1: 273-294.

Dirickson, W. 1976. Ecology and physiological aspects of reproductive strategies in two lizards. Ecology, 57/3: 445-458.

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Lovern, M. 2000. Behavioral ontogeny in free-ranging juvenile male and female green anoles, Anolis carolinensis, in relation to sexual selection. Journal of Herpetology, 34/2: 274-281.

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Miller, W., M. Wolbarsht. 1962. Neural activity in the parietal eye of a lizard. Science, 135/3500: 316-317.

Milstead, W. 1965. Lizard Ecology: A Symposium. Columbia, Missouri: University of Missouri Press.

Oliver, J. 1951. "Gliding" in amphibians and reptiles, with a remark on an arboreal adaptation in the lizard, Anolis carolinensis carolinensis Voigt. The American Naturalist, 85/822: 171-176.

Orrell, K., J. Congdon, T. Jenssen, R. Michener, T. Kunz. 2004. Intersexual differences in energy expenditure of Anolis carolinensis lizards during breeding and postbreeding seasons. Physiological and Biochemical Zoology, 77/1: 50-64.

Rohrilich, S., R. Rubin. 1975. Biochemical characterization of crystals from the derman iridophores of a chamelean Anolis carolinensis. The Journal of Cell Biology, 66/3: 635-645.

Ruby, D. 1984. Male breeding success and differential access to females in Anolis carolinensis. Herpetologica, 40/3: 272-280.

Sexton, O., C. Hoger, E. Ortleb. 1966. Anolis carolinensis: effects of feeding on reaction to aposematic prey. Science, 153/3740: 1140.

Sigmund, W. 1983. Female preference for Anolis carolinensis males as a function of dewlap color and background coloration. Journal of Herpetology, 17/2: 137-143.

Smith, H. 1946. Handbook of Lizards. Ithaca, New York: Comstock Publishing Company.

Vanhooydonck, B., A. Herrel, R. Damme, J. Meyers, D. Irschick. 2005. The relationship between dewlap size and performance changes with age and sex in a green anole (Anolis caolinensis) lizard population. Behavioral Ecology and Sociobiology, 59/1: 157-165.

Versely, D., M. Hadly. 1971. Calcium requirement for melanophore-stimulating hormone action on melanophores. Science, 173/4000: 923-925.

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