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Overview

Brief Summary

Biology

Galapagos land iguanas are active during the day. They maintain their body temperature by basking in the sun to warm up and seeking shade when they become too hot. In the morning they can be found basking, but during the heat of midday they tend to retreat into shade. At night they sleep in burrows which they dig themselves (5). This species is omnivorous but tends to mainly eat plants and the fruits and pads of cactus trees. They may remove the spines with their claws, and these cacti provide them with plenty of moisture during dry spells (2) (5). This species has an interesting relationship with Galapagos finches; the iguanas often raise themselves from the ground and allow the finches to remove ticks from their bodies (2). Males defend territories, with displays involving head bobbing, biting and tail thrashing (5). During courtship, males aggressively court the females (4). After mating, the females set off on a migration to suitable egg-laying habitat. On Ferdinanda Island, females are known to travel up to 15 km to reach a suitable nesting site (4). They then lay two to 20 eggs in a 50 cm deep burrow. The nest site is guarded for a number of days after laying, in order to prevent other females from laying in the same place and damaging the eggs (5). The young hatch after 85 to 110 days; it then takes them up to a week to dig their way out of the burrow (5). Maturity is reached between eight and 15 years. If they survive the first years of life, when they are most vulnerable to predation and food scarcity, land iguanas can live for up to 50 years (2).
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Description

There are two species of land iguana found in the Galapagos; this species Conolophus subcristatus, is found on six islands and Conolophus pallidus is found only on Santa Fe (2). This species is very large, growing to lengths of over a meter (2). The short head is blunt and the back legs are thick and powerful, with long sharp claws on the toes (4). It is yellowish in colour with blotches of white, black, rust and brown (5) and a row of spines passes along the centre of the neck and back (4).
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Distribution

The Galapagos Land Iguana is native to the Galapagos Islands, off the coast of Ecuador. It is formerly widely distributed on these islands, though its numbers are now greatly reduced (Mattison 1989, Cogger and Zweifel, 1998).

Biogeographic Regions: oceanic islands (Native ); pacific ocean (Native )

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Continent: South-America
Distribution: Galapagos (James = Santiago, Indefatigable = Santa Cruz, Albermarle = Isabella, Narborough = Fernandina, South Seymour) (belongs politically to Ecuador)  
Type locality: Galápagos?
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Range

Land iguanas are endemic to the Galapagos Islands off the coast of Ecuador (4). Conolophus subcristatus is native to six islands (2). In 1835 when Charles Darwin first went to the Galapagos, land iguanas were extremely numerous; he wrote: “I cannot give a more forcible proof of their number, then by stating that when we were left at Santiago Island, we could not for some time find a spot free from their burrows on which to pitch our single tent”. Sadly, this once thriving Santiago Island population has become completely extinct (6).
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Physical Description

Morphology

The Galapagos Land Iguana is yellow or brown in color with spots throughout its ventrum and dorsum. A spikey dorsal crest runs along the neck and back. This is a large (>48 in), heavy bodied lizard, with thick back legs and smaller front legs. There are long, sharp claws on its toes. It has a short blunt head and pleurodont teeth. Its tail is quite a bit longer than its trunk. (Mattison 1989).

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Ecology

Habitat

The lizards live in land burrows, which offer protection from the hot sun. Many islands on which the iguanas live are quite arid.

Terrestrial Biomes: scrub forest

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Habitat and Ecology

Systems
  • Terrestrial
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This iguana lives in the drier areas of the islands on which they occur, in scrubby habitats (5) (4). Females require access to areas of sandy or loose soil in which to lay their eggs; some females even use the ash around dormant volcanic craters (4).
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Trophic Strategy

The Land Iguana is largely a vegetarian. The prickly pear cactus (Opuntia) is a major food source; the lizard eats the cactus fruit and leaves by moving the cactus around in its mouth until all the spines are worked off (Mattison 1989).

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Life History and Behavior

Life Expectancy

Average lifespan

Status: captivity:
15.0 years.

Average lifespan

Sex: male

Status: captivity:
7.3 years.

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Lifespan, longevity, and ageing

Maximum longevity: 15 years (wild)
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Reproduction

These lizards have a mating ritual where the male agressively courts the female. Males defend territories around their burrows that both they and females use as shelter, and most courtship occurs around these burrows. Females are attracted to male's territories with burrows, but these burrows are not used for nesting. (Werner 1982).

Female Land Iguanas lay soft-shelled eggs with permeable shells. About 25 eggs are laid in burrows in moist sand or under leaf litter. On the arid, rocky island of Fernandina, females may travel more than 15 km to find good nest sites, sometimes within the crater of a dormant volcano. When places to lay eggs become scarce, competition between females occurs and some eggs already laid may be disturbed by another iguana (Werner 1983, Mattison 1989). Hatchlings appear in about three to four months, and may take about a week to dig out of the nest cavity (Terraquest 1996).

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Conservation

Conservation Status

The Galapagos Land Iguana is listed as a threatened species by the World Conservation Union (Baillie and Groombridge 1996). Threats include destruction of eggs and young lizards by introduced rats and cats, and destruction of food plants by introduced goats.

IUCN Red List of Threatened Species: vulnerable

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IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
D2

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
World Conservation Monitoring Centre

Reviewer/s

Contributor/s

History
  • 1994
    Vulnerable
    (Groombridge 1994)
  • 1990
    Vulnerable
    (IUCN 1990)
  • 1988
    Vulnerable
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Vulnerable
    (IUCN Conservation Monitoring Centre 1986)
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Status

Classified as Vulnerable (VU D2) by the IUCN Red List (1) and listed on Appendix II of CITES (3).
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Threats

In the early 1800s, whalers and settlers came to the Galapagos Islands. It is likely that they ate land iguanas, but the most serious problem they caused resulted from the introduction, both accidental and deliberate, of predators such as cats and dogs and domestic animals such as goats and pigs (6). Introduced animals are still the main threat facing this species today (2). Cats and rats hunt eggs and young iguanas and introduced goats destroy food plants (4). The natural predators of land iguanas include hawks, herons, and snakes, all of which cannot prey on young after they reach around one year of age, as they become too large. However, cats can continue to kill young iguanas until they reach three or four years of age; cat predation is a huge problem preventing the natural success of the species (5).
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Management

Conservation Actions

Conservation Actions
It is listed on CITES Appendix II.
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Conservation

In 1976, wild dogs wiped out the last colonies of land iguanas around Conway Bay on Santa Cruz Island. This prompted the Charles Darwin Research Station (CDRS) and the Galapagos National Park Service (GNPS) to initiate an emergency rescue scheme for the 60 remaining survivors. They then discovered that a similar level of destruction was occurring on Isabella Island. The GNPS and CDRS established a recovery programme, including a captive breeding scheme based on Santa Cruz. The captive breeding programme continues today, and land iguanas are returned to the wild when they reach a size beyond which they are safe from cat predation (2) (6). This breeding programme is accompanied by a campaign to work towards the eradication and tighter control of introduced animals. Other important measures include the maintenance of suitable habitat for the species, and continued monitoring of the populations (2).
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Relevance to Humans and Ecosystems

Benefits

No adverse effects.

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This species was observed by Darwin early in the 19th Century; Darwin noted its similarity to iguanas on the South American mainland, as well as its obvious adaptations to local conditions. These and other observations of Galapagos wildlife contributed in part to Darwin's theory of evolution.

Today the Land Iguanas are an important part of the unique Galapagos fauna, and studies of their biology, as well as conservation programs, are continuing.

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Wikipedia

Galapagos land iguana

C. pallidus endemic to Santa Fe Island

The Galapagos land iguana (Conolophus subcristatus) is a species of lizard in the family Iguanidae. It is one of three species of the genus Conolophus. It is endemic to the Galápagos Islands, primarily the islands of Fernandina, Isabela, Santa Cruz, North Seymour, Baltra, and South Plaza.[1][2]

Taxonomy[edit]

The Galapagos land iguana varies in morphology and coloration among different island populations.[3] There are two taxonomically distinct forms of Conolophus inhabiting the western part of the islands (C. rosada and C. pallidus) and one in the central part (C. subcristatus).[3] Its generic name, Conolophus, is derived from two Greek words: conos (κώνος) meaning "spiny" and lophos (λοφος) meaning "crest" or "plume", denoting the spiny crests along their backs. Its specific name subcristatus is derived from the Latin words sub meaning "lesser" and cristatus meaning "crested," and refers to the low crest of spines along the animal's back which is not as tall as in most iguanids.

Anatomy and morphology[edit]

Charles Darwin described the Galapagos land iguana as "ugly animals, of a yellowish orange beneath, and of a brownish-red colour above: from their low facial angle they have a singularly stupid appearance."[4] The Galapagos land iguana grows to a length of three to five feet with a body weight of up to twenty-five pounds, depending upon which island they are from.[5][6] Being cold-blooded, they absorb heat from the sun by basking on volcanic rock, and at night sleep in burrows to conserve their body heat.[5] These iguanas also enjoy a symbiotic relationship with birds; the birds remove parasites and ticks, providing relief to the iguanas and food for the birds.[2][7]

Diet and longevity[edit]

Feeding
Feeding on fallen cacti leaves

Land iguanas are primarily herbivorous; however, some individuals have shown that they are opportunistic carnivores supplementing their diet with insects, centipedes and carrion.[2] Because fresh water is scarce on the islands it inhabits, the Galapagos land iguana obtains the majority of its moisture from the prickly-pear cactus that makes up 80% of its diet: fruit, flowers, pads, and even spines.[2][5] During the rainy season it will drink from available standing pools of water and feast on yellow flowers of the genus Portulaca.[5][7]

It is estimated that the Galapagos land iguana has a 50 to 60-year lifespan.[2][6]

Reproduction[edit]

Basking

Galapagos land iguanas become sexually mature anywhere between eight and fifteen years of age, depending on which island they are from.[2] Mating season also varies between islands, but soon after mating, the females migrate to sandy areas to nest, laying 2–25 eggs in a burrow 18 inches deep.[2] The eggs hatch anywhere from 90 to 125 days later.[2][6]

On South Plaza Island, where the territories of marine iguanas and land iguanas overlap, the two sometimes interbreed, resulting in a mixture of features from each species; resulting in what is known as a hybrid iguana.[2] The most likely unions tend to be between male marine iguanas and female land iguanas. Despite their long separation time and their being two distinct species from different genera, the offspring are viable, although likely sterile.[2][3]

Population[edit]

It is estimated that between 5,000 and 10,000 land iguanas are found in the Galapagos.[2] These iguanas were so abundant on Santiago Island at one time that naturalist Charles Darwin remarked when it was called King James Island that "...when we were left at James, we could not for some time find a spot free from their burrows on which to pitch our single tent".[5][8] In the years since then, entire populations (including all the animals on Santiago Island) have been wiped out by introduced feral animals such as pigs, rats, cats, and dogs.[2][5]

It has been suggested that a pink morph of the Galapagos population is actually a genetically distinct subpopulation. This would warrant a separate species designation for the pink subpopulation. Subsequent genetic analysis of the pink morphs have suggested that the subpopulation split off from the main C. subcristatus one at least five million years ago.[9][10]

Recovery efforts[edit]

Male
Yellow land iguana at the Charles Darwin Research Station
Galapagos land iguana on North Seymour Island.

Beginning in the early 1990s the Galapagos land iguana has been the subject of an active reintroduction campaign on Baltra Island. These animals became extinct on Baltra by 1954, allegedly wiped out by soldiers stationed there who shot the iguanas for amusement.[2][7] However, in the early 1930s, William Randolph Hearst had translocated a population of land iguanas from Baltra to North Seymour Island, a smaller island just a few hundred metres north of Baltra because he could not understand why no iguanas were present there. Hearst's translocated iguanas survived, and became the breeding stock for the Charles Darwin Research Station captive breeding program which has successfully reintroduced the species to Baltra and a number of other areas.[2] Visitors today frequently see iguanas on both the runway of the Baltra airport or while they cross the road.

References[edit]

  1. ^ World Conservation Monitoring Centre (1996). Conolophus subcristatus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 8 September 2007.
  2. ^ a b c d e f g h i j k l m n Freda (2006). "Land iguanas". Charles Darwin Research Station Fact Sheet. Charles Darwin Foundation for the Galapagos Islands. Archived from the original on 2007-06-06. Retrieved 2007-10-14. 
  3. ^ a b c Rassmann, Kornelia; Markmann, Melanie; Trillmich, Fritz; Tautz, Diethard (2004), "Tracing the Evolution of the Galapagos Iguanas", Iguanas: Biology and Conservation (California: University of California Press): 71–83, ISBN 978-0-520-23854-1 
  4. ^ Darwin, Charles (1989), The Voyage of the Beagle: Charles Darwin's Journal of Researches, New York: Penguin Classics, p. 401, ISBN 978-0-14-043268-8 
  5. ^ a b c d e f Rogers, Barbara (1990), Galapagos, New York: Mallard Press, p. 51, ISBN 978-0-7924-5192-1 
  6. ^ a b c Rosenthal, Ellen (1997), "Days and nights of the iguana: in the Galapagos, a devoted pair work to save land iguanas", Animals, retrieved 2007-10-16. 
  7. ^ a b c Kricher, John (2006), Galapagos: A Natural History, New Jersey: Princeton University Press, pp. 9,51,91,200, ISBN 978-0-691-12633-3 
  8. ^ Darwin (1839), Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. Journal and remarks., London: Henry Colburn, p. 488 
  9. ^ Madrigal, Alexis (2009-01-05). "Pink Iguana That Darwin Missed Holds Evolutionary Surprise". Wired Science. Wired. Retrieved 2009-01-06. 
  10. ^ Gentile, Gabriele; Anna Fabiani, Cruz Marquez, Howard L. Snell, Heidi M. Snell, Washington Tapia, and Valerio Sbordonia (2009), "An overlooked pink species of land iguana in the Galapagos", Proceedings of the National Academy of Sciences (National Academy of Sciences) 106 (2): 507, doi:10.1073/pnas.0806339106, PMC 2626733, PMID 19124773. 
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