iguana
What are the primary characteristics of iguanas?
Where are iguanas commonly found?
What is the diet of the common, or green, iguana?
Which iguana species are critically endangered?
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iguana, any of nine genera and more than 40 species of the larger members of the lizard family Iguanidae. The name iguana, when used generally, is usually referring only to the members of the subfamily Iguaninae. Iguanas are recognized by their relatively large size (with adults of many species surpassing 1 meter [3.3 feet] in length), sharp claws, and long tails. They inhabit tropical forests and grasslands, with most species distributed across warmer areas of southern North America south through Central America and northern South America. Some species are found on Caribbean islands and in Fiji. All iguanas are mainly herbivores and are egg layers, and all have a parietal eye on the top of the head that helps them detect movement above them.
Common, or green, iguana
One of the best-known species is the common, or green, iguana (Iguana iguana), which occurs from Mexico southward to Brazil, with invasive populations established in Florida, the Dominican Republic, Puerto Rico, several smaller islands in the Caribbean Sea, and Hawaii (see also Why Are Iguanas Falling from Trees in Florida?). Males of this species reach a maximum length of over 2 meters (6.6 feet) and 8 kg (17.6 pounds). It is often seen basking in the sun on the branches of trees overhanging water, into which it will plunge if disturbed. The green iguana is green with dark bands that form rings on the tail; females are grayish green and about half the weight of males. Iguanas also possess atrophied venom glands that produce a harmless venom.
Food of the green iguana consists largely of leaves, buds, flowers, and fruits, particularly those of fig trees (genus Ficus), although many other trees are also fed upon. Although this lizard has a well-developed digestive system housing bacteria that ferment plant material, it also eats invertebrates when young and has been known to eat small birds, mammals, and carrion.
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During the rainy season, males become territorial, and mating pairs are established. At the end of the rainy season, eggs are fertilized and then laid in clutches of up to 65 in the ground during the early dry season. After an incubation period of roughly 90–120 days, the hatchlings emerge. During this time, eggs and young are vulnerable to predators such as coatis and other omnivores. Adult iguanas have been used as food by humans for thousands of years and are threatened by hunting and habitat loss. In rural areas they are a major source of protein.
Other iguanas
Two genera inhabit the Galapagos Islands: the marine iguana (Amblyrhynchus) and a terrestrial form (Conolophus). Marine iguanas are blunt-snouted, with a crest of spines that extend from the top of the head down the back to the base of the tail. They have flattened tails that aid in swimming and diving in their pursuit of underwater algae, which is their primary food source. They can grow up to 1.3 meters (4.3 feet) long and weigh up to 1.8 kg (4 pounds). Their scales are typically colored black to ashen-gray, but those of males can become various shades of green or red, depending on the subspecies. The latter genus includes the Galapagos pink land iguana (C. marthae), which inhabits the slopes of Wolf Volcano on Isabela (Albemarle) Island, the Barrington, or Santa Fé, land iguana (C. pallidus) on Santa Fé island, and the Galapagos land iguana (C. subcristatus), which is native to the islands of Isabela, Fernandina, Santa Cruz, and Plaza Sur.
The most diverse genus is Ctenosaura, which is made up of about 17 species of spiny-tailed iguanas. Some classifications also include the two species of thorntail iguanas, which are endemic to Mexico’s Yucatán Peninsula, in Ctenosaura, whereas others place these two species in their own genus, Cachryx. Other genera include the rock iguanas (Cyclura) of the West Indies, the desert iguanas (Dipsosaurus) of the southwestern United States and Mexico, Fiji iguanas (Brachylophus), and chuckwallas (Sauromalus).
Conservation status
By the second decade of the 21st century, roughly half of all known iguanas were classified as threatened species according to the International Union for Conservation of Nature and Natural Resources (IUCN). Those most at risk of extinction—that is, listed as critically endangered species by the IUCN—include the Utila spiny-tailed iguana (Ctenosaura bakeri), Oaxaca spiny-tailed iguana (Ctenosaura oaxacana), Mona rhinoceros iguana (Cyclura stejnegeri), Jamaican rock iguana (Cyclura collei), Lesser Antillean iguana (Iguana delicatissima), Galapagos pink land iguana (Conolophus marthae), and the Fiji crested iguana (Brachylophus vitiensis).
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