Cyclura is a genus of lizards in the familyIguanidae. Member species of this genus are commonly known as "cycluras" or more commonly as rock iguanas and only occur on islands in the West Indies. Rock iguanas have a high degree of endemism, with in most cases a single species or subspecies restricted to an individual island.
Taxonomy
The genus Cyclura was first circumscribed by Richard Harlan in 1825 to include two new species of lizard: C. carinata and C. teres. C. teres eventually turned out to be a junior synonym of Ctenosaura acanthura. Currently, there are nine described species and eight subspecies identified in this genus.
One author considers the Mona ground iguana to be an independent species, although this has not been accepted by other workers.
Habitat
Rock iguanas most often inhabit subtropical areas of West Indiandry forestbiomes characterized by eroded limestone and sparse vegetation ranging from only moderately dry acacia forest to much drier mesquite and cactus habitats. These are islands made up of heavily eroded limestone which form natural caves.
Diet and longevity
All rock iguanas are herbivorous, consuming leaves, flowers, berries, and fruits from different plant species. Their diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds, and fungi; individual animals do appear to be opportunistic carnivores. A study in 2000 by Allison Alberts revealed that seeds passing through the digestive tracts of C. nubila nubila rock iguanas germinate more rapidly than those that do not. These seeds in the fruits consumed by this species have an adaptive advantage by sprouting before the end of very short rainy seasons. She theorised these iguanas may be an important means of distributing such seeds to new areas. The record for the longest lived captive-born rock iguana is held by a Lesser Caymans iguana, which lived for 33 years in captivity. A blue iguana captured on Grand Cayman in 1950 by naturalist Ira Thompson was imported to the United States in 1985 by Ramon Noegel and sold to reptile importer and breeder, Tom Crutchfield. Crutchfield loaned this iguana to the Gladys Porter Zoo in Brownsville, Texas in 1997. The lizard was named Godzilla by the zoo staff and was kept until his death in 2004. Thompson estimated the iguana to be 15 years of age at the time of its capture. This lizard may have been the word's longest-living recorded lizard at 69 years of age, having spent 54 years in captivity.
Reproduction
All species of Cyclura are sexually dimorphic; males are larger than females, and have more prominent dorsal crests as well as larger femoral pores on their thighs, which are used to release pheromones. The particulars vary slightly among species and subspecies, the rock iguanas reach sexual maturity at three to seven years of age. Females become sexually mature at two to five years of age. Males can be highly territorial with the notable exception of the Exuma Island iguana. Mating takes place at the beginning of or just prior to the first rainy season of the year and lasts for two to three weeks. Females lay from 2 to 34 eggs, with an average clutch size of 17 within 40 days. Females of most species guard their nests for several days after laying their eggs, and incubation lasts approximately 85 days. It has been noted that Cyclura eggs are among the largest lizard eggs produced in the world.
Conservation
In 1996 nine of these taxa were assessed as critically endangered, four taxa are endangered and three species have been identified as vulnerable; one species is believed to be extinct. In addition to small numbers typical of endemic island-dwelling animals, wild populations of these lizards are directly and indirectly impacted by land development, overgrazing by domestic and feral livestock and predation by introduced mammals such as hogs, cats, rats, dogs, and mongooses. In 1990, the American Zoo and Aquarium Association designated the genus Cyclura as their highest priority. Their first project was a captive breeding program for the Grand Cayman iguana, which at the time was the most critically endangered of all the species of Cyclura. The Indianapolis Zoo was involved in research and conservation of all sixteen taxa of West Indian iguanas. This includes collaborative work on establishing baseline biological information in captive and wild iguanas, scientific investigation, conservation efforts, field research and captive breeding programs.
