Reptiles
Anole
Dactyloidae · also called anoles, American chameleon
The anole is the small green or brown lizard on a fence post in the American South, doing push-ups and flashing a pink flag from its throat. That flag, and the sticky toes that let it live in the trees, are the tools behind one of evolution’s most repeated experiments: on island after island in the Caribbean, anoles have diversified into the same set of specialists, over and over.
Overview
Anoles are the family Dactyloidae, more than 400 species, in the Americas and most diverse in the Caribbean. They are small, slender, mostly arboreal lizards with sticky toe pads, a long tail, and — in males especially — a dewlap, a colourful throat fan. All are chiefly insectivores, dashing from a perch to grab flies, crickets, and spiders.
The dewlap
Folded away most of the time, the dewlap swings out on a rod of cartilage into a bright semicircular flag. Combined with push-ups and head bobs in a rhythm unique to each species, it lets an anole advertise its territory, warn rivals, and court females — and lets a watcher tell friend from rival from wrong species.
Not a chameleon
Anoles shift between green and brown with temperature, light, and mood, which earned the green anole the pet name “American chameleon” — but they are not related to true chameleons and the change is slower and narrower. The toe pads grip by the same microscopic mechanism as a gecko’s.
A repeated radiation
From a few founders, Caribbean anoles evolved into twig, trunk, canopy, and grass specialists — and the same set of forms appeared independently on different islands, so a twig anole in Jamaica and one in Puerto Rico look nearly identical without being close relatives. In the US, the native green anole has been pushed higher into the trees by the introduced Cuban brown anole, and has evolved larger toe pads within a few decades in response.
Status
Anoles as a family are Not Evaluated. Common species are abundant, but many Caribbean and Central American anoles are confined to a single island or forest and are threatened by deforestation, hurricanes, and introduced predators, with several Endangered or Critically Endangered.
Anole: common questions
What is a dewlap and what is it for?
The dewlap is the fan of skin under an anole's throat. Normally it lies folded and hidden, but a rod of cartilage in the throat can swing down and forward to spread it into a semicircular flag, often brightly coloured in red, orange, yellow, or blue and sometimes patterned. Anoles use it as a visual signal, combining dewlap extensions with push-ups and head bobs in a display that is distinctive to each species, so that a watching anole can tell whether the displaying animal is a rival male of its own kind, a potential mate, or a different species to be ignored. The dewlap is mainly a male trait used in territorial defence and courtship, though females of some species have a smaller one.
Is an anole a chameleon?
No. The green anole is often sold as an American chameleon or house chameleon because it can turn from bright green to brown, but it is not related to the true chameleons, which are an Old World family. Anoles change colour relatively slowly, over minutes, and mainly between green and brown shades in response to temperature, light, and mood, whereas true chameleons change faster and across a much wider range of colours and patterns for communication and camouflage. Anoles also lack the chameleon's independently swivelling eyes, projectile tongue, grasping feet, and prehensile tail. The two groups have converged only in being arboreal, insect-eating lizards that can change colour to some degree.
How did anoles become so diverse?
Anoles are a textbook case of adaptive radiation, especially on the islands of the Caribbean. A few colonising anoles reached each island and then diversified to fill the available niches, from the ground and grass up through tree trunks to the outermost twigs and the canopy, with each niche favouring a particular set of body proportions — long legs for running on broad trunks, short legs and a slim body for the twig specialists, and so on. Remarkably, the same set of specialist forms, called ecomorphs, evolved separately on different islands, so a twig anole in Jamaica and a twig anole in Puerto Rico are not close relatives but look nearly identical, having each evolved from that island's own ancestor. This repeatability makes anoles a key study system in evolutionary biology.
Are anoles good pets, and what do they need?
Green and brown anoles are inexpensive and often a child's first reptile, but they are small, quick, easily stressed, and not suited to frequent handling, being better as an animal to watch than to hold. They need a tall, planted enclosure with branches, live plants or good fake ones, and space to establish perches, a warm basking spot with UVB lighting, daily misting for humidity and drinking, because they lick water droplets rather than drink from a bowl, and a varied diet of appropriately sized live insects such as crickets, fruit flies, and small roaches, dusted with calcium. Keeping two males together leads to constant fighting.