All About the Iguanas: The Spiky Lizards

Leave a comment / / Updated on: 11th November 2023

Scientific nameIguanidaeWeight6 kilograms (13.2 pounds)
Pronunciationi-gwaa-nuhsLength2 meters (6.6 feet)
ClassificationReptilia, Squamata, & Iguania LocationNorth America, Central America, South America and Australia

The Iguana

Green Iguana sitting in a tree | crisserbug via Getty Images

Iguanas are sluggish, cold-blooded lizards native to the Americas. 

The name applies specifically to the two species within the Iguana genus, but it is also used as the common name for larger members of the family Iguanidae, which includes several genera and species. 

Iguanas are among the largest lizards in the Americas, known for their spiky head and backs. 

They also have long whiplike tails that comprise about half their body length.

Iguanas are widespread and found in various habitats. 

Gage Beasley's In-Demand Plush Toys
Gage Beasley’s In-Demand Plush Toys

The name “iguana” is from “iwana,” the original native name given to this species by the Taino tribe of the Caribbean. 

The different iguana species look and act quite differently,

Iguanas are abundant in the wild, but they’re also commonly kept as exotic pets, which has allowed their introduction into many regions beyond their original range. 

This article explores all the fascinating facts about the iguanas. 

Taxonomy and Classification

Gage Beasley's Green Iguana Lizard Soft Stuffed Plush Toy
Gage Beasley’s Green Iguana Lizard Soft Stuffed Plush Toy

Iguana is the genus name for two iguana species native to the tropical areas of North, Central, and South America. 

The two species within this genus are the common Iguana (Iguana iguana), which is also known as the green iguana, and the Lesser Antillean iguana (Iguana delicatissima). 

But in the broader sense, the name is used as the common name for several other species of large lizards within the Iguanidae family. 

This includes at least eight genera and 30 species. 

Some of the most popular members of this group include: 

  • Desert iguana (Dipsosaurus dorsalis)
  • Marine iguana (Amblyrhynchus cristatus)
  • Galápagos land iguanas (Conolophus)
  • Spiny-tailed iguanas (Ctenosaura)

It is worth noting that not all members of the Iguanidae family are referred to by the common name iguana. 

Smaller species in the family, such as the chuckwallas, are not called iguanas.

The larger members that go by the name iguana are grouped into the subfamily Iguaninae. 

Iguana on a tree branch | Ljupco via Getty Images

Iguanidae is a family within the order Squamata, the largest order of reptiles, which includes several other groups of lizards and snakes. 

The collared lizards (family Crotaphytidae) are the closest living relatives of the Iguanidae group. 

Both groups evolved from the same common ancestors during the Late Cretaceous. 

The two oldest fossil genera in the family are Pristiguana and Pariguana, two iguanid lizards that evolved during the Cretaceous Period. 

The subfamily Iguaninae, which includes all modern iguanas, evolved about 62 million years ago, during the Paleocene Epoch. 

The oldest living genus is the Dipsosaurus, or desert iguanas. 

They evolved during the Eocene Epoch, about 38 million years ago, and are still alive today. 

The Brachylophus genus is also ancient, evolving about 35 million years ago. 

All other modern species of iguana evolved much later in the Neogene Period, about 20 million years ago.

Physical Characteristics

A closeup portrait of a pink shade Iguana | Wirestock via Getty Images

Iguana species have different physical characteristics and adaptations, so much so that you might not recognize them as members of the same family. 

While some have bright, vivid colors, others have a rather dull appearance. 

The differences in their physical characteristics are mainly because they live in various habitats, which has led to each one developing unique adaptations. 

Generally, all iguanas are large lizards with a long whip-like tail and a stocky build. 

Their bodies are somewhat flattened from side to side, which aids in their movement through trees and other arboreal environments.

They tend to have prominent spines along the backs and heads. 

Iguanas have a sprawling posture, with four limbs that end in long, sharp claws. 

They also have a prominent dewlap on their necks. 

The overall size and weight of iguanas vary by species. 

Smaller iguanas can weigh as little as a few ounces, while larger species may weigh several pounds.

The longest iguana is the green iguana (Iguana iguana), with an average length of about five to seven feet (1.5 to 2 meters). 

The longest iguana, the Green Iguana | hsvrs via Getty Images

The smallest is the spiny-tailed iguana (Ctenosaura sp.), which measures about 4.9 to 39 inches (12.5 to 100 centimeters) in length. 

The green iguana weighs anywhere from four to eight kilograms (9 to 18 pounds).

But the heaviest iguana is the blue iguana (Cyclura lewisi), which can weigh up to 30 pounds (14 kilograms). 

In addition to the scaly spine that runs through the midline of their body, iguanas also have different types of scales covering various parts of their body. 

Iguanas are generally difficult to spot because they blend well with their surroundings. 

Most species have greenish or brownish scales that help them blend into their natural environments, whether it’s the forest canopy or rocky terrain. 

Many species can also change their color to blend in better or based on the conditions around them. 

For instance, the banded iguana can change the color of its band from green to blue, gray, or even black. 

Some species also become darker when stressed or during the breeding season. 

Generally, younger iguanas have more vibrant colors, providing better camouflage.

Habitat and Distribution

The iguana family is a large one with several species that live in a wide range of environments. 

Iguanas are primarily found in the Americas, but one genus (Brachylophus) lives in the Fiji Islands of Australia. 

The American iguana species range from the Southwestern United States all the way down to Mexico, Central America, and the Caribbean. 

They’re also found in South America, with a range that goes all the way to the northernmost edge of Argentina. 

Some native American species of iguanas are now found in the Pacific Islands and several countries in Asia due to the exotic pet trade.

The illegal release of these species into the ecosystem makes them invasive species in these places. 

While iguanas tend to have a widespread distribution, a few species are endemic to specific regions. 

Land iguana munching on a cactus flower in Galapagos Island | tirc83 via Getty Images

For instance, the Galapagos pink land iguana (Conolophus marthae) is only found on the Galapagos Islands. 

Similarly, the Grand Cayman blue iguana is endemic to the Grand Cayman Island. 

Iguanas can survive in a range of ecosystems, but they are most commonly associated with tropical and subtropical environments.  

Many species live in the canopies of tropical rainforests and are well-adapted to an arboreal lifestyle.

Some iguanas are also found in savannas, while some species, like the members of the Dipsosaurus genus, are adapted to arid desert environments.

The marine iguana native to the Galápagos Islands is a skillful swimmer.

It lives in coastal regions, including islands and mangrove swamps.

Behavior and Social Structure

A resting iguana, or does it only look like it? | chang via Getty Images

Iguanas are not very active animals. 

Most of them (especially the arboreal species) don’t move around a lot. 

They blend into the forest canopy, where they are less likely to be noticed by predators. 

When they move, their movement is typically sluggish, but they can pick up pace when pursued. 

For instance, the black spiny-tailed iguana can reach speeds of up to 21 miles per hour, which makes it the fastest lizard species. 

Iguanas demonstrate a wide range of adaptations depending on their environments. 

Some species also forage on the ground and have limbs adapted to climbing rocks. 

All Iguana species are ectothermic.

This means their body temperature depends on their environment.  

Consequently, they’re more active during the warmer parts of the day. 

The iguana basking in sunlight | pilesasmiles via Getty Images

In the morning and late afternoon, they bask in the sun to raise their body temperature, which enables them to be more active. 

However, they may seek shade or cooler spots during the hottest parts of the day to avoid overheating. 

Iguanas can be territorial, especially during the breeding season. 

Males often establish territories that they actively defend from other males. 

Territorial behaviors may include head bobbing, push-ups, and the display of the dorsal crest.

In some species, especially during the breeding season, males and females may form temporary pair bonds. 

This pairing often lasts only for the duration of reproduction.

While some species of iguanas are sedentary, others may exhibit seasonal movements in search of food, breeding grounds, or more suitable climatic conditions. 

Marine iguanas, for instance, have been observed migrating between feeding and nesting areas on the Galápagos Islands.

Diet and Feeding

What you got there, iguana? | Christina Williger via Getty Images

Iguanas are herbivorous lizards. 

Their diets vary based on the plant life available within their ecosystem. 

Leaves, flowers, and fruits form the bulk of their diet, but may also feed on plant stems and soft plant bark.

Marine iguanas have a unique diet of marine algae. 

They are among the very few reptile species capable of foraging underwater.

Although they mainly feed on plant materials, some iguanas may occasionally prey on insects or small invertebrates. 

This is particularly true for juvenile iguanas that require more protein during growth.

Lunch time for this iguana! | Gerald Corsi via Getty Images

They start out life as omnivores but soon adapt to an entirely herbivorous diet as they mature. 

Most iguana species forage in trees. 

They use their long, agile limbs and claws to climb trees or navigate through vegetation to access fresh leaves, flowers, and fruits.

Iguanas have serrated teeth and a toothless beak, which aids in cutting and tearing leaves. 

The scaly skin of Iguanas, especially those in arid or semi-arid environments, helps them conserve water efficiently. 

They can extract moisture from the plants they consume and have highly concentrated urine to minimize water loss.

Reproduction and Life Cycle

A couple of Green Iguanas during mating | thejack via Getty Images

Like other lizard species, iguanas engage in elaborate courtship displays to attract females. 

These displays may include head bobbing, push-ups, and visual cues like inflating throat pouches. 

Some species also change color to attract females. 

The intensity and specifics of these rituals can vary between species.

During the breeding season, males establish territories to secure access to mates. 

Females typically control large territories where they nest. 

Males compete against other males for their own territories within these areas and mark the places they have won with pheromones. 

Female iguanas are polyandrous. 

They may choose mates within their territories based on the dominance or attractiveness of these males.

Mating typically occurs during the dry season.

Shimmering vibrant colours and diversity of species such as this Green Iguana juvenile | pilesasmiles via Getty Images

This ensures that the offspring hatch during the wet season when food will be in plentiful supply. 

During copulation, the male inserts his hemipenis into the female’s cloacal vent.

Female iguanas can store sperm in their body for several years. 

This allows her to continue producing fertilized eggs even without males within her territory. 

Copulation typically takes place on the ground or in branches. 

It is worth noting that the specifics of mating tend to differ for the different species of iguanas. 

Iguanas are oviparous, which means they lay eggs. 

Females dig a nest hole up to three feet deep into the ground, deposit their eggs, and cover them with soil. 

Even tree-dwelling iguana species return to the ground to lay their eggs. 

Iguana in front of its nest in Isla Isabela | piccaya via Getty Images

Females can band together to share a nest in locations with limited suitable nesting grounds.

The number of eggs per clutch can vary but usually ranges from a few to around a dozen, depending on the species.

The incubation period for iguanas is typically between 70 and 105 days. 

After this, the 7.6 centimeters (3 inches) long hatchlings emerge from the nest. 

Parental care is non-existent in most iguana species. 

This means the hatchlings are left to develop on their own.

Iguanas grow rapidly, but their growth patterns can vary by species. 

As they grow, iguanas shed their skin repeatedly to accommodate their increasing size. 

Their diet also shifts from a more protein-rich diet in early life to an herbivorous diet as they mature. 

Ecological Role and Interactions

Green Iguana eating some leaves | piccaya via Getty Images

Iguanas are herbivorous. 

They feed primarily on plant materials such as leaves, flowers, and fruits.

Their feeding habits and activities have several ecological implications.

As they feed, iguanas prune vegetation, shaping the structure and growth pattern of plant communities within their ecosystem. 

This can also influence the distribution of plant species and the availability of resources to other animals. 

Like many other herbivores, iguanas can also act as seed dispersers. 

Spiny tail iguana eating an apple in the pacific | Charles Wollertz via Getty Images

They consume fruits and excrete the seeds at different locations, contributing to the spread of these plant species. 

This is beneficial to the diversity and distribution of plants within their ecosystems.

Smaller iguana species, particularly hatchlings, are prey for various predators, contributing to the food web within their ecosystem.

Typical predators include birds, mammals, and other reptiles. 

Some iguanas (especially ground-dwelling species) dig burrows or nest holes in the ground. 

These holes can serve as a refuge for other small animals, including other reptiles, amphibians, or terrestrial invertebrates.

Conservation Status and Threats

Spiny Tailed Iguana on a tree in Guanacaste | SondraP via Getty Images

The conservation status of iguanas varies, depending on the species in question. 

For instance, the common iguana and spiny-tailed iguana are currently listed as species of least concern on the IUCN Red List of endangered animals. 

However, other species, like the Galapagos pink land iguana, are critically endangered. 

The Fiji banded iguana and Grand Cayman blue iguana are also listed as endangered on the IUCN red list. 

Habitat loss due to human activities such as deforestation, agriculture, and urban development are among the biggest threats to iguanas. 

These activities have led to the loss of various critical habitats and fragmented iguana populations in the places where they’re typically found. 

The introduction of invasive species, such as feral cats, rats, and snakes, also poses a threat to iguanas, as these invasive predators can impact their population and distribution. 

This is particularly true for iguanas that live on previously unoccupied islands. 

Iguanas are sometimes illegally captured and traded as exotic pets. 

In some regions, they’re hunted for their meat, skin, and other body parts. 

A fierce looking golden colored Galapagos Land Iguana | Joesboy via Getty Images

This exploitation can have detrimental effects on the wild populations of these reptiles. 

Some iguana species are currently protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). 

This law regulates the international trade of these reptiles as pets and prevents exploitation.

Efforts are also being made to protect and conserve the habitats of iguana species. 

This includes establishing protected areas, reserves, and sanctuaries where iguanas are known to inhabit.

Some of the conservation and breeding programs for various endangered iguana species have been successful. 

For instance, the San Diego Zoo Wildlife Alliance started a recovery program for the Grand Cayman blue iguana (Cyclura lewisi) in 2002. 

Through this program, the organization has boosted the population of this iguana species from just 25 to over 500. 

This is just one of several organizations working to protect the population and diversity of Iguanas in the Americas. 

Unique Adaptations and Survival Strategies

Going up, says the iguana | pilesasmiles via Getty Images

Iguanas have well-developed limbs that are adapted for climbing and grasping branches. 

This is particularly true for species that live an arboreal lifestyle. 

Ground-dwelling species also use their limbs to climb rocks and are adept at burrowing. 

Like other reptiles, iguanas have excellent vision. 

They have well-developed eyes that allow them to detect motion and see colors. 

In addition to their two regular eyes, iguanas have a third eye at the back of their head. 

This is known as a parietal eye. 

Although this eye cannot discern shapes and colors, it can sense changes in light and detect movement. 

Close-up of the iguana and its eyes | Fery Fernady via Getty Images

This makes it easier for iguanas to anticipate predators that may want to attack from behind or above. 

When threatened, iguanas can take a defensive stance to intimidate an attacker. 

They can also whip their long muscular tails to deliver a painful strike. 

Some species can bite if cornered. 

Additionally, iguanas can detach their tails if caught by a predator.

This allows them to escape while the predator is left with just the tail.

Iguanas have venom glands, but this has become atrophied in modern species. 

The venom they produce is practically harmless. 

Cultural Significance and Human Interactions

Iguana at the Wakodahatchee Wetlands in Delray Beach, Florida. | Joel Auerbach via Getty Images

Iguanas are popular reptiles in Central and South America, where they interact with various native tribes. 

Consequently, this lizard is frequently mentioned in myths, folklore, and religions associated with these indigenous cultures. 

Iguanas are considered symbolic animals, and some cultures attribute some spiritual power to them. 

In some Caribbean cultures, their presence is believed to be a positive omen and a symbol of good luck and protection. 

In places where they’re not considered scared, iguanas are often hunted for their meat, skin, and other body parts. 

Iguana meat is a famous delicacy in parts of Mexico, the USA, and Central America. 

The eggs of this lizard are also frequently consumed in some parts of Latin America, such as Colombia and Nicaragua. 

Some iguana species, especially the green iguana, are kept as exotic pets. 

However, they have specific care requirements and can be challenging to keep in captivity.

Future Prospects and Research

Marine iguana with the local birds | reisegraf via Getty Images

Scientists have always been interested in studying the evolutionary history and unraveling the relationship between iguanas and other reptilian species. 

These studies are important because reptiles are among the oldest living animals on Earth, and ancient animals like the iguanas can shed some light on the life of many extinct species. 

Studies in recent years have also focused on understanding the diversity and population structure of iguanas. 

Conservationists need this information to make better decisions about breeding and reintroduction programs to protect endangered species and help their populations rebound.


Iguanas are large lizards within the family Iguanidae. 

They are the largest lizards in the Americas and are found across various habitats in North, Central, and South America. 

Iguanas vary considerably in size, physical characteristics, and behavior. 

They’re relatively sedentary ectothermic lizards, and their level of activity depends on conditions within their environment. 

Iguanas are herbivores with a diet that includes flowers, leaves, fruits, seeds, and other plant materials. 

Most species currently have a stable population; some are even kept as exotic pets in some places.

However, a few species are currently at risk of extinction, and they require urgent intervention to protect the population and ensure their long-term survival.


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