Scientific Name Iguana iguana
Conservation Status Not listed
While known as the green iguana this species can also be a bright orange though they are more often a shade of green. Females and young are more brightly coloured than adults. Their colour can change throughout the day so they can heat up easier the morning by being darker. This ability is not as effective as in other lizard varieties such as chameleons. Around their tail are black bands.
In addition to the two eyes on the front of their head iguanas have a parietal eye which is a sense organ behind the head. It aids their sex organs, thyroid gland and endocrine gland in maturing. It is only able to see shadows which are above them.
Hanging from under the throat is a dewlap. This is more present in males than females and when stiffened can be used for territorial defense and to help them absorb and release heat.
Running down the back and along the tail is a spiny crest. This serves as a defense against predators.
The tail can measure up to 1.3m (4.2ft). If a predator grips onto this they can break it off and it will eventually regenerate. It takes about a year to grow back but is not normally the same length as the orginal.
Females are slightly smaller than males. Males measure 35-42cm (14-16.5in) long from head to the start of the tail while females measure 30-38cm (12-15in). In total they measure 1.2-1.7m (4-5.6ft) long. An average male weighs 4kg (8.8lb) while the females weigh between 1.2 and 3kg (2.6 and 6.6lb).
In captivity green iguanas will regularly live for up to 20 years. In the wild they generally don’t make it past 8 years old.
Green iguanas are omnivores. The majority of their diet is composed of green leafy plants, flowers and ripe fruit. In their first three years of life the green iguana needs much more protein in their diet which they get by eating insects and spiders. These are only eaten periodically by adults who may also scavenge for the odd bit of carrion. Some adults will also cannibalize juveniles.
Water is gained from two sources, firstly from the food which they eat and secondly from licking condensation off of leaves.
South and Central America are the native homes of the green iguana. Here they can be found from Mexico down to Paraguay and Brazil. They can also be found on the islands of Grenada, Curaçao, Trinidad and Tobago, St Lucia, St Vincent and Útila.
Introduced populations of this species can now also be found on Grand Cayman, Puerto Rico Martinique and the United States Virgin Islands. They can also be found in the United States, states of Florida, Hawaii and Texas.
While not originally found on the island of Anguilla a hurricane uprooted trees in 1995 which then drifted to the shore. On these came a colony of green iguanas who still exist on the island today.
Iguanas spend most of their time in the canopy of tropical forests and mangrove swamps. Most of their habitat is close to water. They will not enter deep forest as the sun there cannot incubate their eggs effectively.
Breeding takes place during the spring at the start of the dry season. A male will defend a territory in which several females will reside. He will display to the females by extending his dewlap, bobbing his head and doing “push-ups.” A waxy pheromone produced by the femoral pore is also used to mark their territory and their females. During a breeding season he can mate with several females.
Mating is quite brutal with the male biting the back of the female’s neck to hold her in place.
Around 65 days after mating females find a nesting site where they can dig a nest 0.5-1m (1.6-3.2ft) deep. Into this she will deposit between 20 and 71 eggs. Following laying she leaves and has no further association with the hatchlings.
It takes three months of incubation before the young iguanas will emerge from their eggs. At birth they are about 30cm (1ft) long and are a brighter green than they will be as adults. To get out of their egg they use a caruncle, which is special egg tooth. Within a few days of hatching this drops off.
Survival rates are incredibly low. Only about 35% of eggs laid hatch due to predation and incubation difficulties. Of these only about 2.5% of hatchlings will live past their first year.
For the first two weeks of their life the young iguana can live off of absorbed yolk.
Sexual maturity can vary greatly from two years old to five years old.
Adult green iguanas are only preyed upon by humans. Juveniles may be eaten by large birds or adult iguanas. To defend against predators green iguanas have a range of mechanisms. One is that they will sit above the water and when a predator comes drop from their tree. As adept swimmers they can then get away quickly. They are able to spend 30 minutes underwater. Their tail also serves as a whip and can be dropped if grabbed by a predator.
Their main vocalization is a hiss made during confrontations.
Most of their day is spent basking in the trees to achieve a good temperature for digestion. They generally live in the trees only descending to lay eggs and switch trees.
Green iguanas use their two nostrils to expel the excess salt which accumulates in their body.
Green iguanas are one of the United States most popular pets. In their native range this species has been farmed to satisfy the demand for them and reduce the pressure on wild populations.
Where the green iguana is eaten they are often referred to as the “chicken of the tree.”
By Cayambe (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
By Cary Bass (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons