Author: Neil Losin

Green Anole

Appearance: Anolis carolinensis is a beautiful green lizard, growing to approximately 8 inches in length, including the tail. Males are larger than females and have proportionally larger heads. The dewlap is usually pink (but can also be grayish or greenish), and is much larger in males than in females. Green anoles can undergo dramatic color changes, from bright green to dull olive, brown, and even yellowish. For this reason, many people in Florida call them “chameleons,” although the green anole’s color-changing ability is modest compared to the true chameleons (Chamaeleonidae) of Africa and Madagascar. 

Ecology and Habitat: The green anole’s body shape is that of a trunk-crown ecomorph. But with no other native anoles sharing its range in the southeastern U.S., it historically ranged from the ground to the treetops, making it more of a habitat generalist than Greater Antillean trunk-crown anoles. Today, it shares much of its range with the brown or festive anole (A. sagrei), a Cuban species introduced to Florida around the turn of the 20th century. Many observers believe that the brown anole is driving a decline in green anole populations. This may be true in some places, but another possibility is that green anoles spend more time in the trees where they coexist with brown anoles. In fact, in areas where these two species coexist, the green anole is usually seen on higher perches than the brown anole (which, as a trunk-ground ecomorph, is typically found within a couple of meters of the ground).

Green anoles are active foragers, moving around trees and shrubs in search of prey. They primarily eat insects and spiders, but will also prey on small vertebrates, consume fruit, and even drink nectar from flowers.

Geographic Range and Biogeography: Anolis carolinensis lives throughout the southeastern U.S., from Florida to North Carolina on the Atlantic coast, and west along the Gulf coast through Texas, all the way to the Rio Grande.

Its closest relative is the Cuban trunk-crown species, A. porcatus. Genetic analyses show that the green anole is probably descended from A. porcatus populations from western Cuba, which probably dispersed over water to Florida. The extent of genetic differences between A. porcatus and A. carolinensis suggest that these two species have evolved independently for at least 6 million years, which means that humans played no role in the original colonization of North America by the ancestors of today’s A. carolinensis.

Finally, the green anole itself has become established in many places outside its native range, probably because of its popularity in the pet trade. Today, you can find A. carolinensis in the Pacific (Hawaii, Guam, Palau, and other islands), the Caribbean (Grand Bahama, Anguilla, Grand Cayman), and in southern Japan.

Research Highlights

Anolis carolinensis is a very well-studied species. In a charming 1876 paper titled “The Florida Chameleon,” the Rev. S. Lockwood recounts detailed observations of his pet green anole, a lizard he called “Nolie,” and concludes that the green anole “…is everything that is commendable; clean, inoffensive, pretty, and wonderfully entertaining; provoking harmless mirth, and stirring up in the thinker the profoundest depths of his philosophy.”

Since the late 19th century, biologists have learned a great deal about the green anole, and it has become a model organism for studying many aspects of reptile biology, including the regulation of behavior and reproduction by hormones, social behavior and communication, and the biology of regeneration (because, like most anoles, the green anole can lose and re-grow its tail). In 2011, because of its key role in many subdisciplines of biology, the green anole became the first reptile species to have its entire genome sequenced.

A few recent studies are particularly fascinating. Recall that green anoles coexist with invasive brown anoles (A. sagrei) in parts of their range (see Ecology and Habitat above). In a 2014 study, Yoel Stuart, Todd Campbell, and colleagues studied these two species in Florida by introducing brown anoles to a subset of small, manmade islands that were already inhabited by green anoles. They found that not only did green anoles move to higher perches on the islands they shared with brown anoles, but that over a period of 15 years, the green anoles evolved larger toe pads and more toe pad lamellae (both traits associated with better climbing ability). This may be the best evidence yet that competition between anole species can drive their evolutionary diversification.

Green anoles were in the news again after a 2017 study by Shane Campbell-Staton and colleagues. Studying green anoles in Texas, they measured the lizards’ cold tolerance before and after the winter of 2013-2014, when Texas experienced an abnormally cold “polar vortex” event. Their results show that the extreme cold caused natural selection on the anoles, with southerly populations exhibiting greater cold tolerance after the 2014 polar vortex, on average, than before. Campbell-Staton also used cutting-edge genetic techniques to identify some of the genes that may be involved in cold tolerance.

Species account author: Neil Losin

For more information:
Anolis carolinensis at Animal Diversity Web
Anolis carolinensis at Encyclopedia of Life