Galapagos Land Iguana
The Galapagos Land Iguana (Conolophus subcristatus) is a species of lizard in the Iguanidae family. 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, Hood and South Plaza.
The Galapagos Land Iguana varies in morphology and coloration among different island populations. 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). 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
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." 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. 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. 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.
Diet and longevity
Land iguanas are primarily herbivorous; however, some individuals have shown that they are opportunistic carnivores supplementing their diet with insects, centipedes and carrion. 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. During the rainy season it will drink from available standing pools of water and feast on yellow flowers of the genus Portulaca.
Galapagos Land Iguanas become sexually mature anywhere between eight and fifteen years of age, depending on which island they are from. 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. The eggs hatch anywhere from 90 to 125 days later.
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. 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.
It is estimated that between 5,000 and 10,000 land iguanas are found in the Galapagos. 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". 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.
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.
Reasons for decline
The biggest threat to Galapagos Land Iguanas is from feral animals introduced by humans to the islands. Feral dogs and cats attack the iguanas and destroy their nests; the iguanas, having lived in isolation for millions of years, never developed any instincts to flee from predators. Feral pigs destroy the nests of iguanas while searching for food and even eat the eggs of the lizards. This is common in Cerro Azul volcano and Isabela, and in Santiago pigs may be the cause of the disappearance of the land iguanas that were so abundant when Darwin visited. Introduced goats are a major competitor for food and water; and overbrowsing by goats also leads to loss of protective cover from birds of prey such as the Galapagos Hawk.
Beginning in the early 1990s the Galapagos Land Iguana is the subject of an active re-introduction 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. 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. Visitors today frequently see iguanas on both the runway of the Baltra airport or while they cross the road.
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