That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

The Green Iguana (Iguana iguana) is truly a study in contrasts.  Captive-bred by the millions on farms in Latin America, the 7-inch-long hatchlings are widely considered to be suitable for novice reptile keepers.  Indeed, with proper care, they mature into one of the most impressive and responsive of all reptilian pets.  Yet these tropical lizards have very specific needs that must be met if they are to thrive, and their eventual size (4-6 feet) and potentially aggressive behaviors are serious considerations.

Range and Habitat

The Green Iguana’s range extends from southern Mexicothrough Central America to Paraguay. They also inhabit Puerto Rico, St. Lucia and other Caribbean islands, and have been introduced to Florida and Hawaii (please see this article on Iguana-Raccoon Interactions in Florida).

Green Iguanas are always found near water, into which they plunge when frightened. They are often associated with forested areas, so I was surprised to encounter large populations in Venezuela’s treeless llanos region; please see this article.

Behavior

Green Iguanas are ever-alert, and easily startled by noises, dogs and other threats. They vary greatly in personality – some become docile, while others remain wary of people.

Males may become dangerously aggressive with during the breeding season (please see article below), and either sex may bite, lash out with the tail, or scratch.  The wound on my arm, pictured in the attached photo, resulted from a single flick of the tail (and my skin is generally described as “very leathery”!).  Please write in for information on safe handling.

Housing

Setting up the Terrarium

Enclosure size is a major concern.  Hatchlings will exceed 2 feet in length in their first year, and 3 feet by age 2.  Adults reach 4.0 to 5.5 feet in length, with males sometimes exceeding 6 feet.

Hatchlings may be started in a 30 gallon aquarium, but will need a 55 gallon tank within 12 months.  Once your lizard reaches 3 feet in length, a homemade or commercial cage will be necessary.  An enclosure measuring 6 x 3 x 6 feet tall will suffice for an adult; wheels should be added to allow for sun exposure.  Predator-proof outdoor cages such as modified bird aviaries are the ultimate in “luxury accommodations”.

Green Iguanas are highly arboreal and will be stressed if kept in enclosures that do not allow climbing opportunities.  Stout branches and wooden shelves should be provided.

If an “iguana proof” room is available, out-of-cage exercise time can add greatly to your lizard’s quality of life.

Substrate

Cypress mulch has been used with success, but impactions due to substrate ingestion are possible.  Newspapers, washable cage liners or outdoor carpets are preferable.

Females without access to suitable nesting sites may retain their eggs; please see this article for information on captive breeding.

Light

Green Iguanas will not thrive without a source of Ultra-Violet B light.  Natural sunlight is best, but be aware that glass and plastic filter out UVB rays, and fatal overheating can occur very quickly.

If a florescent bulb is used (the Zoo Med 10.0 UVB Bulb is ideal), be sure that your pet can bask within 6-12 inches of it.  Mercury vapor and halogen bulbs broadcast UVB over greater distances, and also provide beneficial UVA.

Heat

The ambient air temperature should range from 82-95 F, with a basking spot of 95-100 F.  Incandescent bulbs should be used to maintain these temperatures.  A ceramic heater or red/black night bulb can be used after dark.

Humidity

Green Iguanas favor humidity levels of 65-75%, but must be able to dry off as well.  The terrarium should be misted as needed.  A reptile humidifier may be used in especially dry environments.

A large water bowl should be provided for drinking and soaking.

Companions

Males will fight savagely, and females may also battle for dominance.  Juveniles usually get along, but must be watched carefully as they mature.

Feeding

Strict attention to diet is essential if you are to succeed with Green Iguanas.  Nutritional deficiencies can develop quickly, and are difficult to treat. Young iguanas should be fed daily; 2 small meals are preferable to 1 large.  Adults can be fed every-other-day, or provided smaller daily meals.

Greens, Vegetables and Fruit

The majority of your iguana’s food – 60% or more – should consist of a variety of fibrous, calcium-rich vegetables such as kale, romaine, dandelion, bok choy, collards, mustard and turnip greens, beet tops and escarole; broccoli, peas, squash, beans, carrots, peppers and mixed frozen vegetables may be added in smaller quantities.  Spinach binds calcium and should be avoided.

Fruit should not comprise more than 10% of your iguana’s diet.  Bananas, pears, apple, figs, melons, berries, kiwi, peaches and others should be offered.

Boiled brown rice or fiber-rich, sugar free cereals (i.e. Fiber One) may be given as a fiber source. This may not be necessary if a variety of fibrous greens are provided, but serves well as “insurance”.

Protein

In their natural environment, young Green Iguanas consume both insects and vegetation before switching to a plant-based diet as they mature.  While success has been had by using insects as a protein source for young iguanas, most keepers are better off relying upon legumes, such as boiled lentils or pinto, navy and kidney beans.  These should make up 5-10% of the diet until age one, after which time they can be used as occasional treats.

A number of commercial iguana diets are available.  While their long-term use as a sole diet has not been studied, adding some to your iguana’s salad should provide additional nutrients.

Supplements

Most meals provided to growing iguanas should be powdered with a Calcium source such as Zoo Med ReptiCalcium.  Reptivite or a similar vitamin/mineral supplements should be used 2-3 times each week.  The supplementation needs of adults vary; please write in for further information.

Health Considerations

Due to their size, Green Iguanas are sometimes allowed to wander at will about the home.  While a room that has been carefully set up for your iguana (please write in for details) can be useful, free-ranging iguanas present serious health and safety risks.  Chief among these are the potential for fires (dislodged lamps, etc.) and an increased risk of Salmonella transmission.  Please write in for further information. Read More »

Please see Part I of this article for notes on constructing a practical outdoor nesting area for Green Iguanas (Iguana iguana).

Nests with Underground Access

Some breeders (and commercial farms) prefer to provide an underground entranceway into the garbage can nest site (Please see Part I), which is more in keeping with the Green Iguana’s habit of constructing a nesting chamber at the end of a long tunnel.  Read More »

Classified within the family Iguanidae we find some of the most the world’s most popularly kept lizards, such as the Green Iguana (Iguana iguana) and the Chuckwalla (Sauromalus obesus).  As we will see, this diverse group is also populated by a number of oddities as well – rare island dwellers and lizards that dive into icy ocean waters to munch on seaweed, for example.

Species Diversity

The family Iguanidae originally contained over 700 species.  Recent work by taxonomists at the American Museum of Natural History has left the family with 36 species.

The 36 family members range from the United States south through Central America to Paraguay, and also inhabit the Galapagos Islands, West Indies and Fiji.

Habitats

Most are terrestrial but a number are habitat specialists – i.e. the rock-dwelling Chuckwallas, the arboreal Green Iguana and the ocean-dwelling Marine Iguana (Amblyrhnchus cristatus).

All are diurnal, oviparous (egg-laying) and largely herbivorous, although some invertebrate prey is taken, especially by young animals.  Iguanids range in size from the 6 inch Desert Iguana to the 6.5 foot Green Iguana.

A Seagoing Iguana

The Marine Iguana must surely be the strangest lizard in the family, if not the world.  Indigenous to Ecuador’s Galapagos Islands, it feeds entirely on submerged marine algae (“seaweed”).

The water surrounding these tropical islands is very cold, arising as it does from the Humboldt Current.  Under normal circumstances, a lizard entering such water would be rendered immobile within minutes. The Marine Iguana, however, slows its heart’s action to ½ of the normal rate when diving for food, thus limiting the amount of blood that circulates to its outer surfaces (where it would cool rapidly).

After feeding, Marine Iguanas increase their heart rate and bask in the sun to warm up.  Other adaptations to a marine existence include nasal glands that expel seawater, partially webbed feet and a laterally compressed tail.

The unique ticks that parasitize these ocean-going iguanas are hunted by brilliantly-colored crabs that clamber over the lizards’ bodies as they bask – one can only imagine what the first people to view such a scene might have thought!

Endangered Island Dwellers

All 8 species of Rhinoceros Iguana (Cyclura spp.) are limited to specific islands in the Caribbean, such as Cuba, Hispaniola, Jamaica, the Caymans and the Bahamas, and all are critically endangered.  Threats include hunting, habitat loss due to development and the grazing of feral goats, and predation by introduced dogs, cats and rats.  A number of zoos and governments are working on breeding, predator removal and reintroduction programs.

Several species of Rhinoceros Iguanas are also being bred in the pet trade, a fortunate circumstance which has helped to remove collecting pressure on wild populations.  Large and highly intelligent, captive Rhinoceros Iguanas require room-sized enclosures or outdoor aviary-type pens.

Feral, Pet and Food Trade Iguanas

The Green Iguana, long a pet trade staple despite its large size, is also an important food animal and is farmed throughout Latin America.  Escaped and released pets have established large breeding populations in southern Florida and on the Florida Keys.

Native to Central and South America, several of the 14 species of Spiny-tailed Iguanas (Ctenosaura spp.)are common in the pet trade.  Escapees have established breeding populations in southern Florida and on several of the Florida Keys.

Further Reading

Information about each member of the family Iguanidae is posted at here.

In the future I’ll write about the captive care of individual Iguanids, including my favorites, the chuckwalla and desert iguana.

Iguana in Mexico image referenced from wikipedia and originally posted by Keith Pomakis
Marine Iguanas image referenced from wikipedia and originally posted by Aquaimages

A Control Program Backfires
Please see Part I of this article for background information. With introduced green iguanas (Iguana iguana) driving endangered burrowing owls from their nests and raccoons (Procyon lotor) devouring sea turtle eggs, the Florida Department of Environmental Protection initiated control measures. At a preserve in Dania Beach, an intensive trapping and collection campaign greatly reduced the numbers of both species, but an unexpected consequence of these efforts soon became apparent.Within a year of the raccoon numbers being brought under control, iguana populations skyrocketed. In one area of the park, researchers counted 626 iguanas per square kilometer (0.4 square miles)…an unprecedented density for any lizard species!

It seemed that raccoon predation had been a very effective control on iguana numbers. Although hawks, gray foxes, night herons, alligators and other animals prey upon iguanas, only raccoons take eggs, hatchlings and sub-adults in significant numbers.

Iguanas…Here to Stay?
Young iguanas are now especially common at the site, pointing towards an even greater population increase in the future. Hand-collection, although possible, is a daunting task, so biologists are looking into alternate control measures. Meanwhile, spurred by ample food and little competition, lizards as young as 2 years of age are laying eggs.

In Belize, black rats effectively control one green iguana population by taking nearly every egg laid. However, Florida’s parks already have enough problems without black rats…in fact, their notorious cousin, the Norway rat, is already a resident of many!

Further Reading
It was my good fortune to work with green iguanas in a natural, if somewhat unusual (i.e. treeless) habitat. Please see my article, The Green Iguana on the Venezuelan Llanos  for the story.

To learn more about the challenges and rewards of keeping these impressive lizards, please check out our care guide, Green Iguanas.

 

Released and escaped green iguanas (Iguana iguana) have now established huge populations in southern Florida. Although I must admit to a certain degree of fascination with introduced species, there can be no doubt that the massive lizards have caused a great many problems in their adopted environment.

An Impressive but Bothersome Invader
Normally arboreal, iguanas adapt to treeless environments by commandeering burrows occupied by the endangered burrowing owl (Athene cunicularia), displacing the birds and destroying eggs and chicks in the process. Ever hungry, the 4-6 foot long behemoths also assist the spread of undesirable invasive plants by eating their fruits and dispersing the seeds in their feces.

Among one of their most troublesome characteristics is a propensity to colonize airway strips and nearby areas. Green iguanas in Puerto Rico have caused runway accidents, and they are considered a collision hazard in Florida airports as well.

Raccoons in Cities and Nature Preserves
Raccoons, although native, have also become problematical in recent years. Now well adjusted to people, they thrive everywhere…during my years as a nuisance wildlife trapper, I caught scores throughout NYC, including in some of Manhattan’s most densely-populated neighborhoods.

Raccoon populations in south Florida parklands reach 250 animals per square kilometer – 200 times the densities of those dwelling in natural habitats! In addition to serving as a reservoir for rabies and distemper, raccoons in Florida pose a serious threat to the nesting success of green, loggerhead and other marine turtles.

Please check in next week to see how a well-planned control program for both iguanas and raccoons went astray…and would up helping the iguana population to grow astronomically!

Further Reading
Iguanas make fascinating pets, but, as males may exceed 6 feet in length, they are not for the unprepared. Please read our cage guide, Green Iguanas, before you take on one of these impressive giants. Green Iguana image referenced from Morguefile.