9 Illuminating Facts About Iguanas

Iguanas are among the largest lizards in the Americas. These highly adaptive animals are found in a variety of environments, including tropical forests, arid deserts, and even in the water. While most iguanas eat a variety of plants, some also add insects and small invertebrates to their diet. After eating, iguanas bask in the sun, not just for warmth, but for the digestive aid basking offers. There are 45 recognized species of these cold-blooded creatures, including several that are endangered.

From changing colors when the need arises to the ability to autotomize the base of their tail to make a quick getaway, here are a few fascinating facts about iguanas.

1. There Are 45 Different Iguana Species

Iguanas are a group of large lizards found in the temperate southern region of North, Central, and South America, the Antilies, Galápagos, and Fiji. They come in a variety of shapes and colors, and can range in size from 5 inches to 6 and a half feet. Iguanas live on land, in rocks, and in trees. Many iguanas are not native to where they currently inhabit.

One of the most recognized species is the green iguana (Iguana iguana), which is by far the most common and widespread iguana species in the Americas. One of the most visually striking members of the Iguanidae family is the Grand Cayman iguana. Also known as the blue iguana, this exquisite blue-hued creature is the heaviest of all iguanas. An especially unusual species is the Galápagos marine iguana (pictured), which can swim underwater.

2. They Love Sunbathing

Whenever the temperature drops below 40 degrees Fahrenheit, the lizards' muscles essentially become paralyzed and they fall into a state of hibernation. This doesn't happen often in the hot tropics of Central America, but in places like southern Florida, where they've been introduced by humans, an unseasonable winter cold snap can cause scores of these scaled critters to lose their grip on tree limbs and fall to the ground.

While it's quite an alarming sight to witness, the tumble doesn't necessarily mean certain death. Most iguanas warm up with the temperature and don’t suffer any ill effects from the fall.

Researchers studying global warming are interested in the cold tolerance exhibited by iguanas and other lizards, particularly those that are not native species. While scientists anticipate that temperatures will trend warmer with climate change, there is also the expectation that temperatures will be more variable; so determining whether the survival of these species in colder temperatures is due to acclimation or natural selection is important.

3. They Hold Their Own in a Fight

Iguanas use their tail for balance while climbing and maneuvering, but these long appendages serve yet another purpose — self-defense. When encountering a predator or other threat, iguanas will distract and bewilder attackers by thrashing their tails. They are also able to automotize, or break off part of their tail, to make a quick getaway. Their tails can grow back in about a year. Many iguana species have few natural predators, but in the event that an animal tries to eat an iguana, its spiky spinal combs make it a difficult meal to swallow.

Male iguanas display aggression against other males to attract females and over basking sites. Physical fights are rare and are usually between equally sized opponents. When fights do occur, they can result in significant damage to both parties.

4. Fiji Banded Iguanas Can Turn Black

This colorful iguana is found only in Fiji. Arboreal creatures, they come in various shades of blue, green, and yellow to blend in with their treetop environment. But if threatened, they can turn black as a warning to predators.

Despite their beauty, Fiji banded iguanas are exceedingly rare. Because of habitat loss and predation by introduced species like mongooses and domestic cats, their numbers have been in steady decline for the past century. This national treasure of Fiji is found on only a few small islands in central Fiji and is listed as endangered.

5. Some Are Excellent Swimmers

While many iguanas are content to lounge on dry land or cling to shady tree limbs, the marine iguana of the Galápagos Islands spends a great deal of time underwater — and adult males can dive up to 100 feet below the surface. The marine iguana thrives on algae that it scrapes from rocks underwater.

Because it’s cold-blooded, the marine iguana has to warm up in the sun’s rays after going for a dip. They are also adapted for rewarming — their dark coloration improves their ability to reabsorb heat. They typically limit their underwater adventures to just a few minutes, but are able to stay underwater for as long as 30 minutes.

6. They Have a Third Eye

Also known as a parietal eye, iguanas have this “eye,” which resembles a scale on top of their heads. Unlike the iguana’s other two eyes, the parietal eye is quite simple in its physiology and can only detect changes in lightness and darkness and sense movement. But it’s more than enough to help iguanas evade predators, as it alerts the reptiles of any impending threats.

The iguanas' two primary eyes are also quite effective, as they provide color as well as distance vision.

7. They Are Herbivores

While some have been known to occasionally feast on insects, most iguanas consume a plant-based diet. Depending on habitat, iguanas eat everything from fruits and green leafy plants to flowers and marine larvae. In addition to plants, rock iguanas eat insects, slugs, land crabs, and carrion. Desert iguanas are folivores, favoring a diet of leaves; but they also eat flowers, buds, and the occasional insect.

In order to expedite their growth, young green iguanas consume spiders and insects during their early years. Basking in the sun is important to iguanas’ digestion, and when temperatures decline, they reduce their food intake.

8. They Can Live for a Long Time

Depending on the species, iguanas can live anywhere from six to over 60 years. The Grand Cayman rock iguana has the longest lifespan — 25 to 40 years in the wild and over 60 years in captivity. In the wild, green iguanas have an estimated lifespan of eight years, though they can survive for 20 years or more in captivity. By comparison, the marine iguana has a short lifespan of just over six years.

9. Some Are Endangered

While some species like the green iguana are widespread in their native and introduced habitats, several other iguana species are vulnerable, endangered, or critically endangered. The Galápagos pink land iguana, with an estimated population of 192 individuals and a range of just over nine square miles, is critically endangered. Much of its population loss is due to rats and feral cats on the island. The Exuma rock iguana, which exists in a popular tourist area of the Bahamas, is critically endangered due to the negative impact of additional visitors to the island as well as changes in the flora and fauna of its native habitat.

Depending on the region, there are different measures that can be taken to improve iguanas’ chances for survival. Galápagos National Park, which the pink land iguana inhabits, has protection in place for the animals. Tourism is not permitted on Volcán Wolf, the Galápagos pink island iguanas’ habitat, and there are active measures in place to eradicate and control invasive animal species on the island. In the Bahamas, the government is discouraging locals from relocating iguanas from their home cays for tourist attractions and informs visitors about the protected Exuma rock iguana by posting signs about the species on the island.