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Brief Summary

    Green iguana: Brief Summary
    provided by wikipedia

    The green iguana (Iguana iguana), also known as the American iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus Iguana. It is native to Central, South America, and the Caribbean. Usually, this animal is simply called the iguana. The green iguana ranges over a large geographic area, from southern Brazil and Paraguay as far north as Mexico and the Caribbean islands. They have been introduced from South America to Puerto Rico and are very common throughout the island, where they are colloquially known as gallina de palo and considered an invasive species; in the United States feral populations also exist in South Florida (including the Florida Keys), Hawaii, the U.S. Virgin Islands and the Rio Grande Valley of Texas.

    A herbivore, it has adapted significantly with regard to locomotion and osmoregulation as a result of its diet. It grows to 1.5 meters (4.9 ft) in length from head to tail, although a few specimens have grown more than 2 metres (6.6 ft) with bodyweights upward of 20 pounds (9.1 kg).

    Commonly found in captivity as a pet due to its calm disposition and bright colors, it can be very demanding to care for properly. Space requirements and the need for special lighting and heat can prove challenging to an amateur hobbyist.

Comprehensive Description

    Green iguana
    provided by wikipedia

    The green iguana (Iguana iguana), also known as the American iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus Iguana. It is native to Central, South America, and the Caribbean. Usually, this animal is simply called the iguana. The green iguana ranges over a large geographic area, from southern Brazil and Paraguay as far north as Mexico and the Caribbean islands. They have been introduced from South America to Puerto Rico and are very common throughout the island, where they are colloquially known as gallina de palo and considered an invasive species; in the United States feral populations also exist in South Florida (including the Florida Keys), Hawaii, the U.S. Virgin Islands and the Rio Grande Valley of Texas.[2][3]

    A herbivore, it has adapted significantly with regard to locomotion and osmoregulation as a result of its diet. It grows to 1.5 meters (4.9 ft) in length from head to tail, although a few specimens have grown more than 2 metres (6.6 ft) with bodyweights upward of 20 pounds (9.1 kg).

    Commonly found in captivity as a pet due to its calm disposition and bright colors, it can be very demanding to care for properly. Space requirements and the need for special lighting and heat can prove challenging to an amateur hobbyist.

    Taxonomy and etymology

    The species was first officially described by Swedish botanist Carl Linnaeus in 1758.[4] In the two centuries since then, numerous subspecies have been identified, but later classified as merely regional variants of the same species.[4]

    Using nuclear and mitochondrial DNA-sequence data to explore the phylogenic history of the green iguana, scientists from Utah Valley State College studied animals collected from 17 different countries.[5] The topology of phylogeny indicated that the species originated in South America and eventually radiated through Central America and the Caribbean.[5] The study revealed no unique mitochondrial DNA haplotypes for subspecific status but did indicate the deep lineage divergence between Central and South American populations.[5]

    The word iguana is derived from a Spanish form of the Taíno name for the species: iwana.[6][7] In some Spanish speaking countries, males of the species are referred to as gorrobo or ministro and juveniles are called iguanita or gorrobito.[8]

    Distribution and habitat

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    Green iguana in Maracaibo

    The native range of the green iguana extends from southern Mexico to central Brazil, Dominican Republic, Paraguay, and Bolivia and the Caribbean; specifically Grenada, Aruba, Curaçao, Trinidad and Tobago, St. Lucia, St. Vincent, and Útila.[9][10] They have been introduced to Grand Cayman, Puerto Rico, Texas, Florida, Hawaii, and the United States Virgin Islands;[10][11][12] and colonised the island of Anguilla in 1995 after being washed ashore following a hurricane. Though the species is not native to Martinique, a small wild colony of released or escaped green iguanas endures at historic Fort Saint Louis.[13]

    Green iguanas are diurnal, arboreal, and are often found near water.[14][15] Agile climbers, Iguana iguana can fall up to 50 feet (15 m) and land unhurt (iguanas use their hind leg claws to clasp leaves and branches to break a fall).[15][16][17] During cold, wet weather, green iguanas prefer to stay on the ground for greater warmth.[8] When swimming, an iguana remains submerged, letting its four legs hang limply against its side. They propel through the water with powerful tail strokes.[8]

    In South and Central America, where the green iguana is native, it is an endangered species in some countries because people have been hunting and eating this “chicken of the trees” for a long time.[18]

    Anatomy and morphologies

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    Skeleton

    Despite their name, green iguanas can come in different colors. In southern countries of their range, such as Peru, green iguanas appear bluish in color with bold blue markings.[15] On islands such as Bonaire, Curaçao, Aruba, and Grenada, a green iguana's color may range from green to lavender, black, and even pink.[7][15] Green iguanas from the western region of Costa Rica are red, and animals of the northern ranges, such as Mexico, appear orange.[7][15] Juvenile green iguanas from El Salvador are often bright blue as babies, but they lose this color as they get older.[7]

    Adult iguanas found on most of St. Lucia, mainly on the northeast coast, Louvette and Grand Anse, have many differences from other green iguana populations. They are light green with predominant black stripes. Instead of the typical orange dewlap, the iguanas of St. Lucia have a black dewlap. When compared to the common green iguana, females lay about half the amount of eggs, 25 instead of 50. Scales to the back of their head, near the jawbone, are smaller. Their iris is white or cream. Other green iguanas have yellow eyes.[19][20]

    Green iguanas possess a row of spines along their backs and along their tails, which helps to protect them from predators.[15] Their whip-like tails can be used to deliver painful strikes and like many other lizards, when grabbed by the tail, the iguana can allow it to break, so it can escape and eventually regenerate a new one.[21] In addition, iguanas have a well-developed dewlap, which helps regulate their body temperature.[16] This dewlap is used in courtships and territorial displays.[7][15][22]

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    Male with spines and dewlap

    Green iguanas have excellent vision, enabling them to detect shapes and motions at long distances.[23] As green iguanas have only a few rod cells, they have poor vision in low-light conditions. At the same time, they have cells called “double cone cells” that give them sharp color vision and enable them to see ultraviolet wavelengths.[23] This ability is highly useful when basking so the animal can ensure that it absorbs enough sunlight in the forms of UVA and UVB to produce vitamin D.[7][17]

    Green iguanas have a white photosensory organ on the top of their heads called the parietal eye (also called third eye, pineal eye or pineal gland), in contrast to most other lizards that have lost this primitive feature.[23] This "eye" has only a rudimentary retina and lens and cannot form images,[23] but is sensitive to changes in light and dark and can detect movement.[23] This helps the iguana detect predators stalking it from above.[23]

    Green iguanas have very sharp teeth that are capable of shredding leaves and even human skin.[7] These teeth are shaped like a leaf, broad and flat, with serrations on the edge. The similarity of these teeth to those of one of the first dinosaurs discovered led to the dinosaur being named Iguanodon, meaning "iguana-tooth", and the incorrect assumption that it had resembled a gigantic iguana.[24] The teeth are situated on the inner sides of the jawbones, which is why they are hard to see in smaller specimens.[22]

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    In Palo Verde National Park, Costa Rica

    Primarily herbivorous, green iguanas are presented with a special problem for osmoregulation; plant matter contains more potassium and as it has less nutritional content per gram, more must be eaten to meet metabolic needs.[25] As green iguanas are not capable of creating liquid urine more concentrated than their bodily fluids, like birds they excrete nitrogenous wastes as urate salts through a salt gland.[25] As a result, green iguanas have developed a lateral nasal gland to supplement renal salt secretion by expelling excess potassium and sodium chloride.[25]

    Green iguanas from Guatemala and southern Mexico predominantly have small horns on their snouts between their eyes and their nostrils, whereas others do not.[15] Naturalists once classified these iguanas as a separate subspecies (Iguana iguana rhinolopha); however, this classification has been found to be invalid based on mitochondrial DNA and iguanas with similar nose projections appear randomly in other populations and interbreed freely with those that do not share this trait.[7][15]

    The green iguana is a large lizard and is probably the largest species in the iguana family, though a few in the genus Cyclura may match or exceed it in weight.[26] Adults typically grow to 1.2 to 1.7 m (3.9 to 5.6 ft) in length from head to tail.[7] As in all iguanas, the tail comprises much of this length, and the snout-to-vent length of most green iguanas is 30 to 42 cm (12 to 17 in). An average adult male will weigh around 4 kg (8.8 lb) while the smaller adult female will typically weigh 1.2 to 3 kg (2.6 to 6.6 lb).[27] A few large males can reach or exceed 6 to 8 kg (13 to 18 lb) in weight and 2 m (6.6 ft) long.[28] Some specimens have even reportedly been measured at a body weight of greater than 20 lb (9.1 kg).[7]

    Reproductive biology

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    Juvenile green iguana
    Grand Cayman

    Male green iguanas have highly developed femoral pores on the underside of their thighs which secrete a scent (females have femoral pores, but they are smaller in comparison to those of the males).[7] In addition, the dorsal spines that run along a green iguana's back are noticeably longer and thicker in males than they are in females, making the animals somewhat sexually dimorphic.[7]

    Male green iguanas tend to display more dominant behaviors, such as head bobbing and tail whipping. They also tend to develop a taller dorsal crest than females, as well as taller dorsal spines (or spikes). Large, round, very pronounced jowls are generally a male characteristic. Jowls are located under the jaw and are protected by the subtympanic plate, which is a large, green, circular-shaped scale.

    Green iguanas are oviparous with females laying clutches of 20 to 71 eggs once per year during a synchronized nesting period.[21][29] The female green iguana gives no parental protection after egg laying, apart from defending the nesting burrow during excavation.[29] In Panama, the green iguana has been observed sharing nest sites with American crocodiles and in Honduras with spectacled caimans.[10]

    The hatchlings emerge from the nest after 10–15 weeks of incubation.[21][29] Once hatched, the young iguanas look similar to the adults in color and shape, resembling adult females more so than males and lacking dorsal spines.[29]

    Juveniles stay in familial groups for the first year of their lives.[29] Male green iguanas in these groups often use their own bodies to shield and protect females from predators and it appears to be the only species of reptile which does this.[30]

    Behavior

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    Reddish colored green iguana

    When frightened by a predator, green iguanas will attempt to flee, and if near a body of water, they dive into it and swim away.[8] If cornered by a threat, the green iguana will extend and display the dewlap under its neck, stiffen and puff up its body, hiss, and bob its head at the aggressor.[15] If threat persists the iguana can lash with its tail, bite and use its claws in defense.[8] The wounded are more inclined to fight than uninjured prey.[8]

    Green iguanas use "head bobs" and dewlaps in a variety of ways in social interactions, such as greeting another iguana or to court a possible mate.[7] The frequency and number of head bobs have particular meanings to other iguanas.[15]

    Green iguanas are hunted by predatory birds and their fear of these is exploited as a ploy to catch them in the wild.[8] The sound of a hawk's whistle or scream makes the iguana freeze and it becomes easier to capture.[8]

    Diet

    Iguana eating Bougainvillea leaves

    Green Iguanas are primarily herbivores, with captives feeding on leaves such as turnip greens, mustard greens, dandelion greens, flowers, fruit, and growing shoots of upwards of 100 different species of plant.[7][29] In Panama one of the green iguana's favorite foods is wild plum, Spondias mombin.[8]

    Although they will consume a wide variety of foods if offered, green iguanas are naturally herbivorous and require a precise ratio of minerals (2 to 1 calcium to phosphorus) in their diet.[17][31] It is important for captive iguanas to have a variety of leafy greens along with fruits and vegetables such as turnip greens, collards, butternut squash, acorn squash, mango, and parsnip.[32][33] Juvenile iguanas often eat feces from adults in order to acquire the essential microflora to digest their low-quality and hard-to-process vegetarian-only diet.[8][29]

    There is some debate as to whether captive green iguanas should be fed animal protein.[7] There is evidence of wild iguanas eating grasshoppers and tree snails, usually as a byproduct of eating plant material.[34][35] Wild adult green iguanas have been observed eating birds' eggs.[9] Zoologists, such as Adam Britton, believe that such a diet containing protein is unhealthy for the animal's digestive system resulting in severe long-term health damage including kidney failure and leading to premature death.[36] On the other side of the argument is that green iguanas at the Miami Seaquarium in Key Biscayne, Florida, have been observed eating dead fish and individuals kept in captivity have been known to eat mice without any ill effects.[7] De Vosjoli writes that captive animals have been known to survive and thrive on eating nothing but whole rodent block, or monkey chow, and one instance of romaine lettuce with vitamin and calcium supplements.[7] However, it is only recommended that captive iguanas not be fed lettuce or meat, and instead receive the vitamins and minerals they need via a purely herbivore diet.

    Captivity

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    A green iguana in a terrarium

    The American pet trade has put a great demand on the green iguana; 800,000 iguanas were imported into the U.S. in 1995 alone, primarily originating from captive farming operations based in their native countries (Honduras, El Salvador, Colombia, and Panama).[37] However, these animals are demanding to care for properly over their lifetime, and many die within a few years of acquisition.[7][38]

    Although green iguanas in captivity will eat meat if presented with it, excessive consumption of animal protein results in severe kidney problems and possible premature death.[7][36] Misinformed pet owners tend to feed iguanas iceberg lettuce, which provides iguanas with water but has no other nutritional value.[17] A captive green iguana's diet should consist of fresh leafy vegetables such as mustard greens, collard greens, dandelion, arugula, or kale and access to fresh water.[7]

    Green iguanas will thrive only in temperatures of 79 °F (26 °C) to 95 °F (35 °C) and must have appropriate sources of UVB and UVA lighting, or else their bodies cannot produce vitamin D that promotes calcium absorption, which can result in a metabolic bone disease that can be fatal.[7][17] In some locales (New York City and Hawaii), iguanas are considered exotic pets, and are prohibited from ownership.[39][40] Due to the potential impact of an introduced species on Hawaii's ecosystem, the state has strict regulations regarding the import and possession of green iguanas; violators can spend three years in jail and be fined up to $200,000.[41]

    As an invasive species

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    Young juvenile iguana, found indoors in Curaçao
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    At the Botanical Garden at Portoviejo, Ecuador

    Caribbean

    In the aftermath of Hurricane Luis and Hurricane Marilyn in 1995, a raft of uprooted trees carrying fifteen or more green iguanas landed on the east side of Anguilla – an island where green iguanas had never been recorded before.[42] These iguanas were apparently accidentally caught on the trees and rafted two hundred miles across the ocean from Guadeloupe, where green iguanas are indigenous.[43][44] Examination of the weather patterns and ocean currents indicated that the iguanas had probably spent three weeks at sea before arriving on Anguilla.[44] This colony began breeding on the new island within two years of its arrival.[44]

    In February 2012, the government of Puerto Rico proposed that the islands' iguanas, which were said to have a population of four million and considered to be a non-native nuisance, be eradicated and sold for meat.[45][46]

    Fiji

    The green iguana is present as an invasive species on some of the islands of Fiji, where it is known as the American iguana. They pose a threat to the native iguanas through the potential spread of disease and to humans by spreading salmonella. They were initially brought to Qamea in 2000 by an American who wanted them to eat the numerous insects on the island, although they are primarily vegetarian. They are now on the islands of Laucala, Matagi and Taveuni.[47][48]

    United States

    The green iguana is established on Oahu and Maui, Hawaii, as a feral species (despite strict legislation banning the importation of any reptiles)[49][50] and the Rio Grande Valley of Texas.[15] As most reptiles carry salmonella, this is a concern and a reason legislation has been sought to regulate the trade in green iguanas.[10]

    Due to a combination of events, the green iguana is considered an invasive species in South Florida and is found along the east coast as well as the Gulf Coast of Florida from Key West to Pinellas County.[10][22][51] The original small populations in the Florida Keys were stowaways on ships carrying fruit from South America.[52] Over the years, other iguanas were introduced into the wild, mostly originating through the pet trade. Some escaped and some were intentionally released by their owners; these iguanas survived and then thrived in their new habitat.[51] They commonly hide in the attics of houses and on beaches. They often destroy gardens and landscaping.[51] They seem to be fond of eating a native endangered plant, Cordia globosa and feeding on nickernut (Caesalpinia) a primary food plant of the endangered Miami blue butterfly (Cyclargus thomasi bethunebakeri); additionally on Marco Island, green iguanas have been observed using the burrows of the Florida burrowing owl, a species of special concern, all of which can make them more of a serious threat to Florida's ecosystem than originally believed.[10][52]

    In January 2008, large numbers of iguanas established in Florida dropped from the trees in which they lived, due to uncommonly cold nights that put them in a state of torpor and caused them to lose their grip on the tree branches.[53] Though no specific numbers were provided by local wildlife officials, local media described the phenomenon as a "frozen iguana shower" in which dozens "littered" local bike paths. Upon the return of daytime warmth many (but not all) of the iguanas "woke up" and resumed their normal activities.[54] This occurred again in January 2010 and January 2018 after a prolonged cold front once again hit southern Florida.[55][56]

    Cultural references

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    Although eating iguanas is forbidden in Nicaragua they are available in markets

    The Moche people of ancient Peru worshipped animals and often depicted green iguanas in their art.[57] The green iguana and its relative the black iguana (Ctenosaura similis) have been used as a food source in Central and South America for the past 7,000 years.[6] It is possible that some of the populations in the Caribbean were translocated there from the mainland by various tribes as a food source.[6] In Central and South America, green iguanas are still used as a source of meat and are often referred to as gallina de palo, "bamboo chicken" or "chicken of the trees,"[8] because they are said to taste like chicken.[58]

    References

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    49. ^ Perry, Brian (2006-04-12), "Leaping lizards! Girl sights iguana in Kahului", The Maui News
    50. ^ Hawaii Dept. of Agriculture News Release – NR09-03, 2009-02-05
    51. ^ a b c Lush, Tamara (2005-07-26), "Florida's Iguana Infestation", St. Petersburg Times
    52. ^ a b Youth, Howard (2005), "Florida's Creeping Crawlers", Zoogoer, 20 (3), archived from the original on 2008-01-01
    53. ^ Cold Snap Causes Frozen Iguana Shower, WESH, 2008
    54. ^ "Alien Iguanas Fall From Florida Trees During Cold Snap", Associated Press, National Geographic Society, 2008
    55. ^ "Cold tightens grip, all the way to Florida iguanas". Associated Press. cleveland.com. January 6, 2010.
    56. ^ "Iguanas are falling out of trees in Florida because it's so cold. Please don't pick them up". Associated Press. washingtonpost.com. January 4, 2018.
    57. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames & Hudson, 1997.
    58. ^ Gruson, Lindsey (22 August 1989). "A Plan to Save Iguanas, and Rain Forests in the Bargain". The New York Times. Retrieved 17 July 2008.

Distribution

    Distribution
    provided by Animal Diversity Web

    Green iguanas, Iguana iguana, occur throughout Central and South America, from Sinaloa and Veracruz, Mexico, south to the Tropic of Capricorn in Paraguay and southeast Brazil. This large lizard also inhabits many islands throughout the Caribbean region and the coastal eastern Pacific, and has been introduced into southern Florida and in Hawaii. This is the largest known lizard to occur within the borders of the United States (Conant and Collins, 1998; Campbell, 1998).

    Biogeographic Regions: nearctic (Introduced , Native ); neotropical (Introduced , Native )

Morphology

    Morphology
    provided by Animal Diversity Web

    Within three years, a young, 12 gram hatchling iguana can become a 1 kg adult (de Vosjoli, 1992). Upon hatching, the length of green iguanas ranges from 17 to 25 cm. Most mature iguanas weigh between 4 and 6 kg, but some in South America, with proper diet can reach up to 8 kg. These large lizards can reach head to tail lengths of around 2 m.

    Although called green iguanas, these animals are actually variable in color. The adults become more uniform in color with age, whereas the young may appear more blotchy or banded between green and brown. Color of an individual may also vary based upon its mood, temperature, health, or social status. Such color alteration may aide these animals in thermoregulation. In the morning, while body temperature is low, skin color will be darker, helping the lizard to absorb heat from sunlight. However, as the hot mid-day sun radiates upon them, these animals become lighter or paler, helping to reflect the sun rays and minimizing the heat absorbed. Active dominant iguanas usually have a darker color than lower-ranked iguanas living the same environment (Frye, 1995). Most color variation seen in this species is exhibited by males, and may be attributed in part to sex steroids. Six to eight weeks prior to and during courtship, males may acquire a bright orange or gold hue, although coloration is still related to dominance status (Frye, 1995). Mature females, for the most part, retain their green coloring.

    Other distinguishing features of this species include a pendulous dewlap under the throat, a dorsal crest made up of dermal spines that run from the mid neck to the tail base, and a long tapering tail. The dewlap is more developed in adult males than females. Extensions of the hyoid bones stiffen and support the leading edge of this structure, which is used in territorial defense or when the animal is frightened. This fleshy structure also serves in heat absorption and dissipation when it is extended.

    The laterally situated eyes are protected mainly by a immovable eyelid and freely mobile lower eyelid (Oldham and Smith, 1975). On the dorsal midline of the skull behind the eyes is a parietal eye. This sense organ, although not a true "eye," serves as a meter for solar energy, and aids in the maturation of sex organs, thyroid gland, and endocrine glands (Frye, 1995). The visual effect of this "eye" is mostly limited to the detection of predatory shadows from above.

    The scales or plates on the head are larger and more irregular than the scales on the rest of the body. Below the tympanum there is a large rounded scale called the subtympanic plate.

    Range mass: 4 to 8 kg.

    Average mass: 7 kg.

    Range length: 2 (high) m.

    Average length: 1.75 m.

    Other Physical Features: heterothermic

    Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful; ornamentation

Habitat

    Habitat
    provided by Animal Diversity Web

    Green Iguanas are arboreal lizards that live high in the tree canopy. Juveniles establish areas lower in the canopies while older mature iguanas reside higher up. This tree dwelling habit allows them to bask in the sun, rarely coming down except when females dig burrows to lay eggs. Although preferring an arboreal (forested) environment, they can adjust well to a more open area. No matter where they inhabit, they prefer to have water around as they are excellent swimmers and will dive beneath the water to avoid predators (Conant and Collins 1998).

    Habitat Regions: tropical ; terrestrial

    Terrestrial Biomes: forest ; rainforest

    Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools; coastal ; brackish water

    Wetlands: swamp

    Other Habitat Features: suburban ; agricultural

Trophic Strategy

    Trophic Strategy
    provided by Animal Diversity Web

    Green iguanas are primarily herbivorous. They occasionally eat a small amount of carrion or invertebrates. Green leafy plants or ripe fruits are their preferred foods.

    Green iguanas use their tongues to help manipulate the food and bite small enough pieces to swallow, with little or no chewing. The food mixes with enzymes in the stomach before moving to the small intestine where pancreatic enzymes and bile are mixed with it. Most digestion occurs in the sacculated colon, where microflora break down the cellulose (Frye, 1995). Microflora are essential for hind-gut digestion of the hard to digest diet of this species. Hatchling iguanas are inclined to eat feces from adults, which may be an adaptation for acquiring this much need microflora (Alberts et.al., 2004). This microflora breaks the food down and makes it available for absorption.

    Iguanas require a high amount of dietary protein in their first two to three years for adequately fast growth. During this time period, young iguanas may consume insects and spiders. Older iguanas that have reached close to maximum growth consume a low phosphorous, high calcium, leafy diet for their maintenance requirements.

    Iguanas are ectothermic. Their body temperature is mainly dependent upon the environmental temperature. Low environmental temperatures inhibit an iguana's appetite and digestive enzymes. Active eating usually occurs when the environmental temperatures are between 77 and 95 degrees Fahrenheit (Frye, 1995). Basking is an important aid to digestion. Iguanas may cease eating prior to or during skin shedding. Females may refuse to eat during later stages of egg development. Individuals who are overly stressed or in a new environment may also refuse to eat.

    Animal Foods: eggs; insects; terrestrial worms

    Plant Foods: leaves; fruit; flowers

    Primary Diet: herbivore (Folivore , Frugivore ); omnivore

Associations

    Associations
    provided by Animal Diversity Web

    In addition to helping disperse seeds, iguanas provide a source of food for larger predatory animals, including humans. Like other amphibians and reptiles, iguanas can be indicators of environmental changes (Kaplan, 2002). Reptiles are more sensitive to environmental changes than are humans, and by watching their responses, we can be alerted to possible problems before they are large enough for us to detect with our own senses.

    Ecosystem Impact: disperses seeds

    Associations
    provided by Animal Diversity Web

    One of the best methods for iguanas to avoid predation is their cryptic coloration. Because they look like so much of their green environment, they can remain immobile when a predator has been spotted, and go unnoticed themselves. Young iguanas may be found in small groups, and use the "selfish-herd" or "more eyes are better" strategy to avoid predators. Iguanas prefer to bask in tree limbs that over-hang water so when threatened by a predator they can dive into the water and swim swiftly away. In addition to these strategies for avoiding predation, green iguanas are able to shed a large portion of their tail, thus distracting predators and allowing the "rest" of the animal to escape.

    Hawks and other large birds are potential predators of juvenile iguanas. Humans are another one of major predators of green iguanas. Humans eat both iguanas and their eggs. Humans also use these reptiles for crocodile bait, and poach them for the pet trade.

    Like many other animals, green iguanas also suffer from habitat destruction.

    Known Predators:

    • Homo sapiens
    • hawks
    • large birds

    Anti-predator Adaptations: cryptic

Behavior

    Behavior
    provided by Animal Diversity Web

    These animals are known to use visual signals, such as head bobbing and dewlap extension, as means of communicating with rivals. In extreme cases, physical contact is involved in altercations. In addition, males scent mark females as well as branches. Hissing, which is a form of auditory communication, sometimes occurs.

    Communication Channels: visual ; tactile ; acoustic ; chemical

    Other Communication Modes: mimicry ; pheromones ; scent marks

    Perception Channels: visual ; tactile ; acoustic ; chemical

Life Cycle

    Life Cycle
    provided by Animal Diversity Web

    Approximately 65 days after mating, a female is ready to lay her eggs. The size and number of eggs produced varies depending upon her size, her nutritional status, and her maturity. Eggs measure around 15.4 mm in diameter, and 35 to 40 mm in length (Frye, 1995). Over a three day period, an average of 10 to 30 leathery white or pale-cream colored eggs are deposited into a nest. Nests are located 45 cm to more than a meter deep, and may be shared with other females if nesting areas are limited. After laying the eggs, females may return to the nest several times but do not stay to guard it.

    Incubation lasts from 90 to 120 days. Temperature should range from 85 to 91 degrees Fahrenheit. The hatchlings pip the egg open using a special egg tooth, called the caruncle, that falls off shortly after hatching. Absorbed yolk provides most of the nourishment for the first week or two of an iguana's life.

    There are no major morphological changes in these animals as they age, except that they grow. However, diet is related to age. The young, with higher need for protein, are more likely to consume insects and eggs than are mature individuals.

Life Expectancy

    Lifespan, longevity, and ageing
    provided by AnAge articles
    Maximum longevity: 19.8 years (captivity)
    Life Expectancy
    provided by Animal Diversity Web

    Iguanas can live for more than 20 years in captivity, although wild iguanas are thought to live only about 8 years. Proper nutrition for growth is a concern for captive management of these animals. Improper housing and nutrition can shorten a captive iguana's lifespan.

    Range lifespan
    Status: captivity:
    20 (high) years.

    Average lifespan
    Status: wild:
    8 years.

    Average lifespan
    Status: captivity:
    10 years.

    Average lifespan
    Sex: female
    Status: captivity:
    12.4 years.

Reproduction

    Reproduction
    provided by Animal Diversity Web

    Most green iguanas reach sexual maturity between three and four years of age, although maturity can be reached earlier. Iguanas tend to breed in the dry season, ensuring that young hatch in the wet season when food is more readily available (de Vosjoli, 1992).

    Mating appears to be polygynandrous. Courtship occurs within a defined territory where more than one female may be present. Conflicts between males are not uncommon. Courtship behavior of males includes head bobbing, extending and retraction of the dewlap, and nuzzling or biting a female’s neck (Frye, 1995). Dominant males may also mark rocks, branches, and females with a waxy pheromone-containing substance secreted from their femoral pores.

    During mating, the male approachs the female and climbs on her back, straddling her. To restrain his mate, he grips the her shoulder skin with his teeth, sometimes causing wounds. The male then pairs his cloacal vent up with the female's and inserts one of his hemipenes into her cloaca. Copulation can last for several minutes. Female iguanas can can save sperm for several years (Frye, 1995), allowing them to fertilize eggs at a much later date.

    Mating System: polygynandrous (promiscuous)

    Females lay their eggs about 65 days after mating (eggs take 59 to 84 days to develop before they are laid). Over the course of three days, females may up to 65 eggs, each measuring around 15.4 mm in diameter, and 35 to 40 mm in length (Frye, 1995). Eggs are deposited into nests which are located 45 cm to more than a meter deep, and may be shared with other females if nesting areas are limited.

    Incubation lasts from 90 to 120 days. Temperature should range from 85 to 91 degrees Fahrenheit. The hatchlings pip the egg open using a special egg tooth, called the caruncle, that falls off shortly after hatching. Absorbed yolk provides most of the nourishment for the first week or two of an iguana's life. Young are independent from birth.

    Timing of sexual maturity varies. Animals may be able to breed as early as their second year, but may not breed until as late as their fifth year.

    Breeding interval: These animals breed annually.

    Breeding season: Green iguanas breed in the dry season.

    Range number of offspring: 65 (high) .

    Average number of offspring: 10-30.

    Range gestation period: 59 to 84 days.

    Average gestation period: 65 days.

    Range age at sexual or reproductive maturity (female): 2.5 to 5 years.

    Average age at sexual or reproductive maturity (female): 3-4 years.

    Range age at sexual or reproductive maturity (male): 3 to 5 years.

    Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; oviparous ; sperm-storing

    Parental investment includes the risk of mating and laying eggs. Eggs are provisioned with nutrients by the mother. Females choose nesting sites, presumably as a means of caring for their offspring. However, after eggs are laid, there is no direct investment in the young.

    Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female)

Conservation Status

    Conservation Status
    provided by Animal Diversity Web

    Although some populations have suffered from poaching and collection for the pet trade, green iguanas are not considered a conservation risk at this time. All Iguana species are listed under CITES Appendix II.

    US Federal List: no special status

    CITES: appendix ii

Benefits

    Benefits
    provided by Animal Diversity Web

    The most adverse effect green iguanas have on humans would be eating exotic tropical foliage in gardens. They do not pose any major problems for humans.

    Benefits
    provided by Animal Diversity Web

    Iguanas are farmed in some countries as a source of food and leather, as well as for the pet trade. Due to their large size, iguana hides provide a source of luxury leather that can be made into boots, belts or purses. The pet industry also prizes iguanas; most are sold in the United States, Europe, and Japan. Iguanas also make an interesting tourist attraction in resort areas.

    Exploitation of iguanas has resulted in marked declines in their numbers in some parts of their range. (Campbell, 1998).

    Positive Impacts: pet trade ; food ; body parts are source of valuable material; ecotourism ; research and education