Green Iguana
Species Description

The Green Iguana (Iguana iguana) is one of the most iconic and widely recognized reptiles in the world, both in their natural habitats and in the exotic pet trade. The common name "Green Iguana" derives from the species' typical bright green coloration displayed by juveniles and many adults, though this can vary significantly with age, locality, and individual variation. In some regions, they are simply referred to as "iguanas" or "common iguanas," though these terms are less specific given the existence of other iguana species.

Scientifically, the Green Iguana belongs to the family Iguanidae, which includes numerous species of New World lizards. The genus Iguana contains only two recognized species: Iguana iguana (the Green Iguana) and Iguana delicatissima (the Lesser Antillean Iguana). Within Iguana iguana, there are two recognized subspecies: I. i. iguana found throughout most of the range, and I. i. rhinolopha, which occurs in parts of Central America and is distinguished by subtle morphological differences including horn-like scales on the snout.

In the pet trade and among herpetoculture enthusiasts, Green Iguanas may be referred to by several informal names including "green iggies," "IGs," or simply "greens" to distinguish them from other iguana species. Color morphs and selective breeding have produced variations sometimes called "red iguanas," "blue iguanas," or "albino iguanas," though these are all variants of Iguana iguana rather than separate species. The species' scientific name dates back to Linnaeus's original description in 1758, making it one of the earliest reptiles to receive formal taxonomic classification.

Green Iguanas are large, impressive lizards that undergo dramatic changes in size and appearance throughout their lives. Hatchlings emerge at approximately 7-9 inches in total length and vibrant green in coloration, while adults can reach 5-7 feet in length, with males typically larger and more robust than females. Adult males commonly reach 6-7 feet and can weigh 15-20 pounds or more, while females generally reach 5-6 feet and weigh 8-15 pounds. The tail comprises approximately two-thirds of the total body length and serves multiple functions including balance, defense, and swimming.

The species' most distinctive feature is the prominent row of spines running along the back from the head to the tail tip, which are most pronounced in adult males. These spines are actually modified scales that can reach 2-3 inches in height on dominant males and play a role in visual displays and thermoregulation. Adult males also develop large dewlaps (throat fans) used in territorial displays and communication, along with pronounced jowls that give the head a bulky appearance. These secondary sexual characteristics become more prominent during breeding season and with age.

Coloration in Green Iguanas is highly variable and changes throughout their lives. Juveniles display brilliant green coloration with faint banding on the body and tail, providing excellent camouflage in tropical vegetation. As iguanas mature, their coloration often shifts toward olive, brown, or even orange hues, particularly in males during breeding season. Some populations and individuals retain bright green coloration throughout life, while others become quite dark or develop striking rust-orange coloration. Color intensity can also vary with temperature, stress level, and health status.

Other notable physical features include large, round eyes with excellent vision, powerful limbs equipped with long toes and sharp claws for climbing, and a third eye (parietal eye) on top of the head that detects light and helps regulate circadian rhythms and thermoregulation. The scales are small and granular on most of the body, with larger, more prominent scales forming distinctive patterns on the head and sides. Males develop large femoral pores on the underside of the thighs that secrete waxy substances used in marking territory and attracting mates. The skin appears leathery and somewhat rough to the touch, requiring appropriate humidity for healthy shedding throughout the animal's life.

Green Iguanas display complex behavioral patterns and temperaments that change significantly throughout their lives and vary greatly between individuals. Juvenile iguanas are typically calm and tolerant of handling, which unfortunately leads many people to acquire them without understanding that adult temperament often becomes more aggressive and defensive. As Green Iguanas mature, particularly males, they frequently develop territorial behaviors, aggression during breeding season, and reduced tolerance for handling. This behavioral shift is driven by hormones and natural instincts rather than improper care, though socialization and handling frequency during juvenile stages can influence adult temperament.

Adult male Green Iguanas become particularly challenging during breeding season, typically occurring in late fall through winter in captivity, coinciding with shorter photoperiods. During this time, males display intense territorial aggression, head-bobbing, dewlap extensions, color intensification, and may attack anything perceived as a threat, including their keepers. Bites from adult iguanas can cause serious injury, requiring stitches, and tail whips can leave painful welts or lacerations. Even outside breeding season, adult iguanas may display dominance behaviors and require experienced handling techniques and appropriate respect for their size and power.

Green Iguanas are primarily diurnal and arboreal, becoming active soon after dawn when they emerge from nighttime retreats to bask in sunlight. In the wild, they spend hours basking in prominent treetop positions where they can monitor their territory and watch for predators. After reaching optimal body temperature, they forage for food throughout the canopy, using their excellent color vision to select tender leaves, flowers, and fruits. In captivity, this natural behavior pattern manifests as morning basking sessions followed by periods of exploration, feeding, and intermittent basking throughout the day.

Social structure in Green Iguanas is hierarchical, with dominant males controlling prime basking and feeding territories. In the wild, multiple individuals may inhabit the same general area, but maintain spatial separation and communicate through visual displays including head-bobs, dewlap extensions, and body posturing. Submissive individuals display slow head-bobs or retreat from dominant animals. This territorial nature means multiple iguanas, particularly males, should never be housed together as serious fighting will occur. Even females may display aggression toward each other in confined spaces.

Defense mechanisms in Green Iguanas are varied and effective. Their primary escape strategy is dropping from trees into water and swimming away with surprising speed and agility, aided by their powerful tail. When cornered or unable to escape, they employ tail-whipping, scratching with sharp claws, and powerful bites. The tail can regenerate if lost, though the new growth never matches the original in length or appearance. Iguanas also use visual displays including lateral body compression to appear larger, darkening of coloration, and mouth-gaping to deter threats. Understanding these defensive behaviors is crucial for safe handling and husbandry, as misreading an iguana's stress signals can result in injury to both keeper and animal.

Housing Green Iguanas represents one of the most significant challenges of keeping this species, as their massive size and arboreal nature demand extremely large, custom-built enclosures that many keepers underestimate when acquiring juveniles. Adult Green Iguanas require minimum enclosure dimensions of 12 feet long x 6 feet wide x 6 feet tall, though larger is always better for animal welfare and behavioral expression. Many dedicated keepers convert entire spare rooms, build custom outdoor enclosures in appropriate climates, or construct large cage systems that can cost thousands of dollars in materials and equipment. The commitment to providing adequate space must be considered before acquiring even a small juvenile, as they reach adult size within 3-4 years.

Vertical space is crucial for Green Iguanas due to their arboreal nature and instinctive behavior of climbing to elevated positions for basking and security. The enclosure should feature multiple horizontal branches, platforms, and climbing structures at various heights, constructed from sturdy materials capable of supporting the full weight of an adult iguana (15-20 pounds or more). Natural hardwood branches like oak or manzanita work well, though they must be thick enough to prevent sagging or breaking. Artificial vines and platforms can supplement natural branches, but ensure all structures are securely mounted as falling injuries can occur. The highest basking area should allow the iguana to reach within 12-18 inches of the primary heat and UVB sources.

Substrate selection for Green Iguana enclosures must prioritize safety, as these large lizards can accidentally ingest particulate substrates during feeding. Recommended options include reptile carpet, tile, sealed wood flooring, or newspaper for ease of cleaning and elimination of impaction risk. Avoid loose substrates such as sand, mulch, or wood chips, particularly for juveniles, as ingestion can cause serious or fatal intestinal blockages. Some keepers use bioactive substrates in extremely large enclosures where the substrate-to-iguana ratio makes accidental ingestion less likely, but this requires expertise in maintaining the bioactive ecosystem. Whatever substrate is chosen, it must facilitate easy cleaning as adult iguanas produce substantial waste.

Temperature regulation is critical for Green Iguana health and requires multiple heat sources to create proper thermal gradients. The basking area should reach 95-100°F, measured with a digital thermometer or temperature gun at the basking surface, while ambient temperatures should range from 75-85°F with a cooler end around 75°F to allow thermoregulation. Nighttime temperatures can safely drop to 70-75°F. Achieving these temperatures in large enclosures typically requires multiple heat sources such as high-wattage basking bulbs, ceramic heat emitters, and radiant heat panels. All heat sources must be protected by guards or placed out of reach to prevent thermal burns. Thermostats are essential for maintaining consistent temperatures and preventing equipment failures from causing dangerous temperature swings.

UVB lighting is absolutely essential for Green Iguana health, as without adequate UVB exposure they cannot synthesize vitamin D3 and will develop metabolic bone disease regardless of calcium supplementation. High-output UVB bulbs specifically designed for large, sun-loving reptiles should be used, such as T5 HO 10.0 or 12.0 bulbs, mounted 12-18 inches from the highest basking area. The entire length of the iguana's body should receive UVB exposure while basking. UVB bulbs must be replaced every 6-12 months as UV output degrades before visible light diminishes. Natural unfiltered sunlight is the ideal UVB source, and outdoor exposure during warm weather provides excellent supplementation, though overheating must be prevented.

Humidity maintenance at 65-75% is necessary for healthy skin, respiratory function, and shedding. In large enclosures, this can be challenging and may require multiple approaches including daily misting with a spray bottle or automated misting system, large water features or soaking tubs, live plants, and monitoring with digital hygrometers placed at different heights. Proper ventilation must be balanced with humidity maintenance to prevent stagnant, excessively humid conditions that can promote respiratory infections or skin issues. Many keepers use programmable humidifiers or misting systems to maintain consistent humidity levels, particularly in dry climates or during winter when indoor heating reduces ambient humidity.

Green Iguanas are strict herbivores throughout their lives, and maintaining proper nutrition is crucial for preventing the numerous health problems associated with improper diet, which is unfortunately common among captive iguanas. In the wild, Green Iguanas consume a varied diet of leaves, tender shoots, flowers, and fruits from dozens of plant species, with seasonal availability dictating specific food sources. They show preference for young, tender vegetation and are particularly attracted to flowers and fruits when available. The natural diet is high in fiber, moderate in protein, and carefully balanced in calcium-to-phosphorus ratios.

In captivity, replicating the nutritional diversity and balance of the wild diet requires daily preparation of fresh salads composed primarily of dark leafy greens with high calcium-to-phosphorus ratios. Staple greens should include collard greens, mustard greens, turnip greens, dandelion greens, endive, escarole, and arugula, which provide excellent calcium and nutrition. These should comprise 80-90% of the diet, with the remaining 10-20% consisting of other vegetables such as squash, bell peppers, green beans, and occasional fruits. Fruits should be offered sparingly due to high sugar content, limited to perhaps 5% of the diet, with options like figs, papaya, mango, and berries being preferable to high-sugar options like bananas or grapes.

Foods to strictly avoid include iceberg lettuce (nutritionally deficient), spinach and chard (contain oxalates that bind calcium), cabbage and broccoli (goitrogens that interfere with thyroid function when fed in excess), and all animal protein. Despite persistent myths, Green Iguanas should never be fed animal-based proteins including insects, eggs, meat, or commercial diets containing animal products, as this can cause serious kidney damage, gout, and other health problems. Their digestive systems are specifically adapted for processing plant material and cannot properly handle animal proteins.

Calcium supplementation is essential for growing iguanas and breeding females, though requirements decrease somewhat for adult males. Dust salads with calcium powder (without added vitamin D3 if proper UVB is provided, or with D3 if UVB is questionable) approximately 3-5 times per week for juveniles and 2-3 times per week for adults. Multivitamin supplementation should be offered once or twice weekly. Over-supplementation can be as harmful as under-supplementation, so moderation is important. The goal is supporting natural vitamin D3 synthesis through UVB exposure rather than relying on dietary D3.

Feeding frequency varies with age and size. Juvenile iguanas should receive fresh food daily, and they typically eat enthusiastically during their rapid growth phase. Adults can be fed every other day, though many keepers continue daily feeding with appropriate portions. Food should be offered in the morning after the iguana has had time to bask and raise body temperature, as proper temperature is necessary for digestion. Remove uneaten food after several hours to prevent spoilage. Fresh water must be available at all times in a heavy bowl large enough for the iguana to soak in, as they often defecate in their water and it requires daily cleaning and refilling.

Green Iguanas face numerous health challenges in captivity, with the vast majority of health problems stemming from improper husbandry, particularly inadequate UVB exposure, improper diet, insufficient space, and inappropriate temperature or humidity. Metabolic bone disease is tragically common in captive iguanas, especially those acquired as juveniles and kept by inexperienced keepers without proper UVB lighting and calcium supplementation. Respiratory infections, parasites, injuries from inadequate enclosures, kidney disease from improper diet, and stress-related conditions are also prevalent. Many health issues develop slowly over months or years before becoming apparent, making preventive care and proper husbandry from day one absolutely critical. A qualified reptile veterinarian should be established before acquiring an iguana, and regular wellness exams can catch problems early when treatment is most effective.

Green Iguanas are extremely demanding animals that frequently develop preventable health problems when kept by inexperienced keepers or in inadequate conditions. The initial appeal of a small, bright green juvenile often leads to poor outcomes when owners realize the extensive care requirements and substantial costs of proper husbandry for these giants. Prospective keepers must commit to providing appropriate housing, equipment, veterinary care, and daily maintenance for 15-20 years before acquiring one of these challenging but impressive lizards. Many rescued iguanas suffer from years of neglect and improper care, making adoption of these animals a serious undertaking requiring extensive resources and experience.

Handling Green Iguanas safely and effectively requires understanding their behavior, respecting their size and defensive capabilities, and adjusting techniques as they mature from calm juveniles to potentially aggressive adults. Juvenile iguanas typically tolerate handling well and benefit from frequent, gentle interaction that helps socialize them to human contact. Daily handling sessions of 10-15 minutes, gradually increasing as the iguana becomes comfortable, help establish trust and allow monitoring of the animal's health. However, keepers must understand that this juvenile docility often changes dramatically as the iguana matures, and handling frequency may need to decrease significantly.

Proper handling technique for Green Iguanas involves supporting the entire body, particularly the chest and hindquarters, never grabbing by the tail which can cause tail autotomy (dropping). Approach the iguana calmly, allowing it to see you and giving it time to recognize you rather than startling it. For adults, wear long sleeves and gloves if needed, as their claws can cause serious scratches even without aggressive intent. Never restrain or pin an iguana as this causes extreme stress and increases likelihood of defensive biting or tail-whipping. If an iguana displays defensive posturing including lateral body compression, mouth gaping, darkened coloration, or tail twitching, respect these warnings and leave it alone. Forced interaction with a stressed or aggressive iguana damages trust and increases danger for both parties.

Shedding is a regular occurrence throughout a Green Iguana's life, with juveniles shedding every few weeks during rapid growth and adults shedding several times annually. Unlike snakes, iguanas shed in pieces rather than whole skin, and the process typically completes within a week or two with proper humidity. During shedding, iguanas may become irritable and have reduced appetite. Resist the temptation to peel shedding skin as this can damage new scales underneath. Instead, increase humidity, provide rough surfaces for rubbing, and offer more frequent soaking opportunities. If shed remains stuck, particularly around toes or tail tip, gentle soaking and careful removal with tweezers may be necessary to prevent constriction.

Routine care tasks beyond handling include daily enclosure spot-cleaning of feces and uneaten food, weekly complete substrate replacement or thorough cleaning, daily water bowl cleaning and refilling, monitoring and recording temperatures and humidity levels, and regular inspection of the iguana for any signs of health problems including abnormal behavior, discharge from eyes or nose, skin lesions, or changes in appetite. Keep detailed records of feeding, shedding, and any health concerns to track patterns and provide information to veterinarians if needed. Regular weighing, perhaps monthly for juveniles and quarterly for adults, helps monitor growth and detect concerning weight loss or gain. These routine care tasks require significant time commitment, particularly as enclosure size increases with the growing iguana.

Green Iguanas are definitively expert-level reptiles that are unsuitable for beginners, children, or anyone unable to commit to extensive space requirements, substantial financial investment, and 15-20 years of demanding daily care. The harsh reality is that thousands of Green Iguanas are abandoned, surrendered to rescues, or euthanized each year when owners realize the enormous commitment required once their cute 10-inch baby becomes a 6-foot dinosaur with attitude. Prospective keepers must be fully prepared for adult size and temperament before acquiring even a hatchling, as the vast majority of people who purchase juvenile iguanas on impulse become unable or unwilling to meet their needs within a few years.

The financial costs of properly keeping a Green Iguana are substantial and ongoing. Initial setup costs easily reach $2,000-5,000 or more for appropriate custom enclosure construction, high-quality heating and lighting equipment, furnishings, and supplies. Monthly costs include electricity for heating and lighting (which can be significant for large enclosures), fresh produce, supplements, substrate replacement, and general maintenance supplies. Annual veterinary wellness exams run $100-300, with emergency veterinary care for sick iguanas potentially costing thousands of dollars. UVB bulb replacement every 6-12 months costs $40-80 per bulb, and multiple bulbs may be needed for large enclosures. These costs continue for the iguana's entire 15-20 year lifespan.

Space requirements make Green Iguanas impossible for most people to properly house. A 12x6x6 foot enclosure is the absolute minimum for an adult, and larger is better. This requires dedicating an entire room or building a substantial custom enclosure, neither of which is feasible for renters, apartment dwellers, or anyone with limited space. The enclosure must be in a temperature-controlled indoor environment in most climates, further limiting placement options. Outdoor enclosures are only viable in tropical or subtropical climates year-round, and even then require protection from temperature extremes and potential predators.

Legal considerations vary significantly by location, with some cities, counties, and states prohibiting ownership of Green Iguanas or requiring permits. Florida, Hawaii, and some other locations classify them as invasive species with strict regulations or outright bans. Before acquiring an iguana, research all applicable laws at city, county, state, and federal levels. Rental agreements often prohibit exotic pets, and even homeowners may face issues with homeowner association rules. Future housing situations must also be considered, as relocating with a large exotic reptile eliminates many housing options. Some jurisdictions restrict outdoor enclosure construction or require permits, adding additional complexity and cost. Given the species' 15-20 year lifespan, keepers must consider how life changes including moves, career changes, or family situations will affect their ability to maintain appropriate care throughout the animal's life.