Iguanas Vs Lizards: Key Differences Explained

Reptiles come in all shapes and sizes, from snakes and turtles to the ever-popular lizards. Lizards are a large and diverse group, with over 6,000 species across the globe. One unique type of lizard is the iguana.

Iguanas may look like your average lizard, but they have several traits that set them apart. If you’ve ever wondered what the main differences are between iguanas and other lizards, you’ve come to the right place.

If you’re short on time, here’s a quick answer: Iguanas are a type of lizard, but they are much larger in size compared to most lizards. Iguanas are also herbivores, while most lizards are carnivores or insectivores.

Iguanas also have dewlaps under their chin and spines down their backs, features many lizards lack.

In this comprehensive guide, we’ll cover all the key differences between iguanas and other lizards in terms of their size, appearance, habitat, diet, behavior, and more. Read on to become a reptile expert!

Taxonomy and Classification of Iguanas vs Other Lizards

Scientific Classification of Iguanas

Iguanas belong to the Iguanidae family, which contains around 40 species of lizard within the Iguania suborder. The two main genera of iguana are Iguana and Ctenosaura. The most common pet species are the green iguana (Iguana iguana) and spiny-tailed iguana (Ctenosaura similis).

Iguanas are therefore classified as:

• Kingdom: Animalia
• Phylum: Chordata
• Class: Reptilia
• Order: Squamata
• Suborder: Iguania
• Family: Iguanidae
• Genera: Iguana, Ctenosaura, etc.

Scientific Classification of Lizards

Unlike iguanas which all belong to the Iguanidae family, lizards constitute a polyphyletic group belonging to many different families. There are around 6,000 lizard species that belong to eight infraorders, including:

• Anguimorpha – monitors, glass lizards, etc.
• Diploglossa – galliwasps
• Iguania – iguanas, agamids, chameleons, etc.
• Gekkota – geckos
• Scincomorpha – skinks
• Lacertoidea – lacertids, amphisbaenids, teiids
• Amphisbaenia – worm lizards
• Xantusiidae – night lizards

Differences in Taxonomy

The key difference in taxonomy between iguanas and other lizards is that iguanas represent a small family of lizard within the Iguania suborder. In contrast, the term “lizard” encompasses many different taxonomic groups across 8 infraorders and numerous families.

While iguanas are quite uniform taxonomically, lizards are extremely diverse. There are at least 80 different lizard families compared to just 1 for iguanas. So while all iguanas are lizards, most lizards are not iguanas.

Size and Appearance

Iguana Size

With an average length of 1.5-1.8 meters (5-6 feet) and weight of 9-10 kg (20 pounds), iguanas are among the largest lizards in the world. The green iguana and Grand Cayman ground iguana reach over 2 meters (6.5 feet) in length as adults.

These sizable reptiles have a tank-like body with a cylinder-shaped torso, long tail, strong legs, and clawed digits adapted for climbing trees.

Lizard Sizes

In contrast to iguanas, most lizards are small, measuring just 5-10 inches long. For example, common house geckos and anoles reach under 8 inches in length. Large lizard species like monitor lizards and Komodo dragons can attain lengths over 3 meters, though they lack the stocky build of iguanas.

Unique Physical Characteristics of Iguanas

Iguanas possess distinctive features including:

Spines running along their back and tail

A loose flap of skin called a dewlap located under the chin, used for temperature regulation and communication

Excellent vision aided by a third eye on top of their head

Flattened tail capable of powerful whiplash to defend against predators

These attributes separate them from other lizards in terms of size, defenses, physiology, and more.

Other Differences in Appearance

As shown in the table, lizards tend to be smaller predators compared to mostly vegetarian iguanas. From chewing teeth to camouflage scales, they also diverge in physical adaptation to their habitats and diets.

Habitats and Geographic Range

Where Iguanas Live

Iguanas are naturally found in tropical and subtropical environments in Central and South America, parts of the Caribbean, and the Galápagos Islands. Common habitats for iguanas include rainforests, woodlands, deserts, coastal beaches, and mangrove swamps.

The different species have adapted to thrive in diverse ecological niches.

For example, the green iguana and spiny-tailed iguana prefer humid rainforests and riparian areas, while the desert iguana and chuckwalla inhabit arid deserts and dry scrublands. Marine iguanas make their home along rocky sea coasts and swim among coral reefs in the ocean.

Overall, iguanas occupy both wet and dry habitats ranging from sea level up to 4,000 meters in elevation.

Lizard Habitats

In contrast to iguanas, lizards occupy an extremely diverse array of habitats around the world. There are over 6,000 lizard species found on every continent except Antarctica. Lizards have adapted to live in rainforests, savannas, deserts, mountains, underground burrows, trees, grasslands, swamps, and intertidal zones.

Some examples of lizard habitats include:

• Tropical rainforests – Chameleons, geckos, skinks
• Deserts – Collared lizards, fringe-toed lizards, zebra-tailed lizards
• Grasslands – Fence lizards, racerunners, whiptails
• Rocky areas – Rock lizards, side-blotched lizards, swifts
• Semi-aquatic areas – Water dragons, basilisks
• Underground burrows – Legless lizards, worm lizards, blind snakes

Lizards have successfully adapted to live in diverse habitats across many latitudes by evolving specializations in body form, temperature regulation, camouflage, and behavior.

Overlap in Geographic Locations

Despite iguanas being restricted to the Americas and parts of the South Pacific, there is some overlap in habitat types occupied by both iguanas and other lizard species. For example, iguanas and lizards both inhabit tropical rainforests in Central and South America.

The green iguana shares the rainforests of Costa Rica with geckos, anoles, and skinks.

Desert habitats are also occupied by both groups, such as in the Southwestern United States and Northern Mexico where desert iguanas overlap with collared lizards and side-blotched lizards. Coastal marine environments with rocky shores and tidepools are home to marine iguanas and other lizards like night lizards in the Galápagos.

Dietary Preferences and Feeding

Iguana Diets

Iguanas are herbivorous, meaning they eat only plant-based foods. Green iguanas enjoy leafy greens like turnip greens, mustard greens, dandelion greens, collard greens, and kale. They also relish veggies such as shredded carrots, bell peppers, squash, peas, and sweet potatoes.

Fruit should make up only 10% of an iguana’s diet. Good fruits options are berries, mango, papaya, and melon.

For optimal health, iguanas need a varied diet rich in calcium. According to the Center for Avian and Exotic Medicine (avianandexoticvets.com), baby iguanas should get a calcium supplement 5 times a week. Juveniles need calcium 3 times a week.

Adult iguanas benefit from calcium dusted on their salad 2 times a week.

What Lizards Eat

Unlike iguanas, most lizards are omnivorous meaning they eat both plant and animal matter. Smaller lizards favor insects like crickets, mealworms, waxworms and occasional treats like pinky mice. Larger species eat rodents, eggs, smaller lizards, frogs, fish and invertebrates.

Some lizards forage for berries, flowers and vegetation.

For pet lizards, providing a balanced, nutrient-rich diet is crucial for good health and proper growth. The Association of Reptilian and Amphibian Veterinarians (arav.org) provides detailed care sheets on the ideal diets for popular lizard species like bearded dragons, blue tongue skinks and leopard geckos.

Differences in Feeding Habits

There are some key differences between iguana and lizard feeding habits and nutritional needs:

• Iguanas only eat plant matter while most lizards are omnivores
• Iguanas need lots of leafy greens and vegetables. Lizards eat more insects, rodents and eggs
• Iguanas require frequent calcium supplements to stay healthy. Lizards need gut loaded insects and a calcium powder a few times a week
• Overfeeding protein can cause health issues in iguanas. Lizards need high protein diets
• Iguanas tend to be grazers, eating small amounts throughout the day. Many lizards prefer one or two larger feedings

In the wild, iguanas forage vegetation while lizards hunt for small prey. As pets, providing species-appropriate diets is essential for keeping these reptiles healthy and happy!

Reproduction and Life Cycles

Iguana Reproduction

Iguanas reach sexual maturity at around 2-4 years old, depending on their species. The breeding season usually coincides with the rainy season of their natural habitats. Dominant alpha males will mate with several females, who lay clutches of 20-70 eggs in burrows dug in sandy banks or soil.

The eggs incubate for 10-12 weeks before hatching.

Baby iguanas are called hatchlings. They receive no parental care and must fend for themselves right away. Hatchling mortality rates are high due to predation and lack of resources. Those that survive will continue growing rapidly for their first few years.

Many species double in size after just one year. Their rapid growth helps them avoid predators.

Lizard Reproduction

There is huge diversity in lizard reproductive strategies. Small lizards may reach maturity in 4-6 months, while the larger monitor species take 4-5 years. Gestation periods range from just 4-6 weeks for geckos to over one year for monitors.

Unlike mammals, female lizards do not feed their young with milk. So once the eggs are laid, the offspring must hunt and forage on their own as soon as they hatch.

Desert species like the Gila monster have adapted to breeding only once every two years since resources are scarce. Tropical species can produce multiple clutches per year. Clutch sizes range from just 2 eggs for monitor lizards to over 20 for smaller species like swifts and spiny-tailed lizards.

Parental care is very rare in lizards.

Comparing Life Stages and Lifespans

Both iguanas and lizards take 2-5 years to reach sexual maturity depending on species size. Small species may only live 5-7 years total, while large iguanas and monitors can live over 15 years. In captivity with ideal conditions, ages of 25+ years have been recorded for iguanas and monitors.

For more details on iguana breeding cycles, see this reference: San Diego Zoo – Iguana Reproduction. And for more on monitor lizard reproduction, check out Encyclopedia Britannica – Monitor Lizards.

Behaviors

Iguana Behavioral Traits

Iguanas are relatively solitary reptiles that prefer to be alone most of the time. They are primarily herbivorous and spend much of their day basking in the sun, foraging for leafy greens, flowers, and fruits. Here are some key behavioral traits of iguanas:

• Territorial – Male iguanas often behave aggressively to defend their territory from other males during breeding season.
• Sun-loving – Iguanas need exposure to UVA and UVB rays to synthesize vitamin D. They frequently bask in the sun.
• Cold-blooded – Like all reptiles, iguanas rely on external heat sources like the sun to regulate their body temperature.
• Good climbers – Their claws, tail, and strong legs enable them to be excellent climbers of trees and rocks.
• Good swimmers – Iguanas are also agile swimmers that can stay submerged for up to 4 hours.
• Communicate through body language – Iguanas use head-bobs, dewlaps, tail whips, and changes in color to signal aggression, courtship, territoriality etc.

In captivity, iguanas may behave aggressively during handling, especially males in breeding season. Taming them from a young age is important. With proper care, iguanas can make for fascinating pet reptiles.

Lizard Behavioral Traits

Unlike the solitary iguana, most lizards are fairly social reptiles that interact with other members of their species. However, behaviors vary greatly among the over 6,000 lizard species. Here are some common behavioral characteristics:

• Communicate through visual signals – Most lizards use body language like head-bobs, push-ups, tail wags, and throat puffing to signal territory, courtship, aggression etc.
• Cold-blooded – Lizard behavior revolves heavily around basking in the sun to absorb heat and regulate body temperature.
• Warmblooded – But some lizards like leatherback sea turtles have adapted to maintain warmer body temperatures.
• Diurnal – Most lizard species are active during the day and sleep at night.
• Insectivorous – Most lizards are carnivorous and eat insects, spiders, worms, snails, small vertebrates etc.
• Oviparous – Most lizard species are oviparous or egg-laying. But some species like skinks are viviparous and give birth to live young.

Pet lizards like leopard geckos, blue-tongued skinks, and bearded dragons exhibit fascinating behaviors like glass-surfing, arm-waving, head-tilting, and circling. Their behaviors need to be carefully interpreted to ensure proper husbandry.

Key Behavioral Differences

While iguanas and lizards share many common reptilian traits, their behaviors differ in aspects like social interactions, diet, habitat preference, aggression, and locomotion. Understanding these dissimilarities is key to meeting their respective care needs in captivity and appreciating their adaptations in the wild.

Conclusion

As we’ve learned, iguanas have several distinct features that set them apart from other lizard species. While they fall under the broad category of “lizard,” iguanas have a unique taxonomy, much larger size, herbivorous diets, dewlaps, spines down their backs, and more.

However, iguanas do overlap with other lizards in terms of their geographic range, sharing habitats in the Americas and Caribbean islands. They also have similarities in their reproductive systems and behaviors like basking in the sun.