Green iguana (Iguana iguana)

Also known as: Common iguana
KingdomAnimalia
PhylumChordata
ClassReptilia
OrderSquamata
FamilyIguanidae
GenusIguana (1)
SizeAverage total length: 1.2 – 1.7 m (2)
Maximum total length: 2 m (3)
Male average snout-vent length: 35 – 42 cm (2)
Female average snout-vent length: 30 – 38 cm (2)
Male weight: 4 kg (4)
Female weight: 1.2 – 3.0 kg (2)

Listed on Appendix II of CITES (1).

The green iguana is one of the best-known reptiles due to its popularity in zoos and with private reptile keepers (3). It has a very distinctive appearance, with a large head, a pronounced dewlap, and an impressive crest of comb-like spines that runs down the centre of the back and tail (3) (5), measuring around three centimetres high (2). While, like its name suggests, this iguana is usually a shade of green, (from dull, grassy green to vivid turquoise), bright orange individuals may occur in the northern parts of its range (3), and the colour may also vary with temperature, particularly when young, being bright green when hot and dull and dark when cold (2). The green iguana’s scaly skin is either uniformly coloured, or bears blackish stripes or a contrasting brownish pattern (3). Prominent large, circular scales are present on the lower jaw below the clearly visible tympanum. Male green iguanas can be distinguished from females by the more pronounced spiny crest and larger head (5), the more noticeable femoral pores (2), and the broader cloaca opening (6).

The green iguana has a wide distribution ranging from the Mexican states of Sinaloa and Veracruz, through Central America and into South America as far south as Peru, Paraguay and northern Argentina, including many neotropical islands (4).

Green iguanas most commonly inhabit tropical forest close to water (3), from sea level up to an altitude of 1,000 metres (4), although they avoid areas of deep forest where the sun cannot reach the ground to incubate the nest (2).

Primarily a tree-dwelling reptile (3), the green iguana is a specialised leaf-eater, consuming the tender green leaves and flowers of a selection of trees, shrubs and herb vegetation (4). For over 90 percent of the time, green iguanas are inactive and often when they do move, they travel slowly. However, if required, green iguanas are capable of running fast and will dive into water to escape predators (4), revealing their excellent swimming abilities. This explains the iguana’s preference for habitat close to watercourses (3).

Green iguanas are territorial during the breeding season (4), and will defend their home range against intruders (3). If a green iguana ventures into the territory of another it will be met firstly with pronounced head-nodding behaviour, believed to be an intimidating action. This may be followed by an extensive threat ritual, when the iguanas vertically flatten their bodies and erect their dorsal crests to create the appearance of being much larger. If the altercation does not end there, serious fights with injuries can follow. The dewlap, which can be lowered by a bone in the neck, is also used in threat displays, as well as for communicating with other green iguanas (3).

Green iguanas breed during the dry season, during which time a territorial male occupies his territory with several females (4). A month or two after mating, the females move to communal nesting sites where they lay a clutch of 17 to 76 eggs in burrows dug into the ground. Iguana hatchlings emerge from the nest after three months of incubation, coinciding with the onset of the rainy season, a strategy to ensure plentiful, lush, green vegetation for the growing iguanas to feed on (4). Green iguana hatchlings are incredibly vulnerable to predators, including other reptiles, birds and mammals (7), and only about 2.6 percent live to the age of one year. Sexual maturity is reached after two to three years (4).

Throughout Latin America, the green iguana is hunted for its beautiful, commercially-valuable skin, prized flesh, and eggs (4) (8). It is one of the neotropical reptiles most frequently hunted for food, to feed the family or for sale, and is killed by rifles or captured by dogs. They are also captured live; newly-hatched iguanas may be exported for the pet trade, while captured females may be cut open to extract the eggs and then released (4); these females subsequently die (2). This level of exploitation, in combination with deforestation, has decimated populations in some parts of its range (4).

There are a number of projects currently underway in Latin America which captive breed green iguanas and release them back to the wild, to supplement the reduced wild populations; for example, the Kekoldi Indigenous Reserve in Costa Rica and Monkey Bay Wildlife Sanctuary in Belize (9) (10). The green iguana is also listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that any international trade should be carefully monitored to ensure it is compatible with the species’ survival (1).

For further information on the green iguana see:

Authenticated (04/06/08) by Jesús A. Rivas, Assistant Professor, Department of Math and Natural Sciences, Somerset Community College, Somerset, Kentucky.
http://anacondas.org

  1. CITES (June, 2007)
    http://www.cites.org
  2. Rivas, J.A. (2008) Pers. comm.
  3. Bosch, H. and Werring, H. (1991) Green Iguanas and other Iguanids. T.F.H. Publications, Neptune, New Jersey.
  4. Ojasti, J. (1996) Wildlife Utilization in Latin America: Current Situation and Prospects for Sustainable Management. Food and Agriculture Organization of the United Nations, Rome.
  5. Capula, M. (1990) The Macdonald Encyclopedia of Amphibians and Reptiles. Macdonald and Co Ltd, London and Sydney.
  6. Rivas, J.A. and Ávila, T.M. (1996) Sex identification in juvenile green iguanas (Iguana iguana) by cloacal analysis. Copeia, 1996: 219 - 221.
  7. Rivas, J.A., Molina, C.R. and Avila, T.M. (1998) Iguana iguana (Green iguana) juvenile predation. Herpetological Review, 29(4): 238 - 239.
  8. Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
  9. Kekoldi Indigenous Reserve (March, 2008)
    http://www.kekoldi.org
  10. Monkey Bay Wildlife Sanctuary (March, 2008)
    http://www.monkeybaybelize.org