Cyclura

Cyclura
Cyclura cornuta, rhinoceros iguana
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Iguania
Family: Iguanidae
Genus: Cyclura
Harlan, 1825

Cyclura is a genus of lizards in the family Iguanidae. 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.[1] Rock iguanas have a high degree of endemism, with a single species or subspecies restricted to individual islands.[2][3]

Taxonomy

The generic name (Cyclura) is derived from the Ancient Greek cyclos (κύκλος) meaning "circular" and ourá (οὐρά) meaning "tail", after the thick-ringed tail characteristic of all Cyclura.[4]

Currently, there are nine described species and eight subspecies identified in this genus.[2][5][6][7][8][9]

Habitat

Rock iguanas most often inhabit subtropical areas of West Indian dry forest biomes characterized by eroded limestone and sparse vegetation ranging from only moderately dry acacia forest to much drier mesquite and cactus habitats.[12] These are nonvolcanic islands made up of heavily eroded limestone which form natural caves that the iguanas use as retreats.[12]

Diet and longevity

Acklin's Island iguana basking on a rock

All rock iguanas are herbivorous, consuming leaves, flowers, berries, and fruits from different plant species.[3] A study in 2000 by Allison Alberts of the San Diego Zoo revealed that seeds passing through the digestive tracts of rock iguanas germinate more rapidly than those that do not.[13][14] These seeds in the fruits consumed by cycluras have an adaptive advantage by sprouting before the end of very short rainy seasons.[14] The iguanas are an important means of distributing these seeds to new areas (particularly if females migrate to nesting sites) and, as the largest native herbivores of many island ecosystems, they are essential for maintaining the balance between climate and vegetation.[14] Their diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds, and fungi; individual animals do appear to be opportunistic carnivores.[3]

Like other herbivorous lizards, the rock iguanas are presented with a special problem for osmoregulation: plant matter contains more potassium and has less nutritional content per gram than meat so more must be eaten to meet the lizard's metabolic needs.[15] Unlike mammals, reptile kidneys cannot concentrate urine to save on water intake. Instead reptiles excrete toxic nitrogenous wastes as solid uric acid through their cloaca.[15] In the case of the rock iguana which consumes large amounts of vegetation, these excess salt ions are excreted through their salt gland in the same manner as birds.[15]

The record for the longest lived captive-born rock iguana is held by a Lesser Caymans iguana, which lived for 33 years in captivity.[16]

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.[17] The lizard was named Godzilla by the zoo staff and was kept until his death in 2004.[17] Thompson estimated the iguana to be 15 years of age at the time of its capture.[17] This lizard may have been the word's longest-living recorded lizard at 69 years of age, having spent 54 years in captivity.[17]

Reproduction

All speciesof 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.[18][19]

Although the particulars vary slightly among species and subspecies, the rock iguanas reach sexual maturity at three to seven years of age.[18] 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.[18] Mating takes place at the beginning of or just prior to the first rainy season of the year (May to June) and lasts for two to three weeks.[18] Females lay from 2 to 34 eggs, with an average clutch size of 17 within 40 days.[18] Females of most species guard their nests for several days after laying their eggs, and incubation lasts approximately 85 days.[18] It has been noted that Cyclura eggs are among the largest lizard eggs produced in the world.[18]

Conservation status

Every species and subspecies of rock iguana is endangered.[14][20] Nine of these taxa are Critically Endangered, meaning there are fewer than 250 of each species or subspecies left in wild populations and in danger of Extinction, four taxa are endangered and three species have been identified as Vulnerable, one species is believed to be extinct in the wild.[2] 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 humans and feral mammals such as hogs, cats, rats, dogs, and mongooses.[2]

Recovery programs

In 1990, the American Zoo and Aquarium Association (AZA) designated the genus Cyclura as their highest priority.[20] 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.[20]

The Indianapolis Zoo is involved in research and conservation of all 16 taxa of West Indian iguanas.[20] This includes collaborative work on establishing baseline biological values in captive and wild iguanas, and scientific investigation, conservation efforts, field research and captive breeding programs.[20] The Indianapolis Zoo has been involved in the Dominican Republic for almost ten years and will continue its research and conservation efforts with the Ricord's iguana.[21]

Grand Cayman blue iguana, Cyclura lewisi

The project's goals are:

References

  1. ↑ Dayhuff, Becky (2006-02-01), "Rock Iguanas of the Caribbean", All at Sea Magazine
  2. 1 2 3 4 Malone, Catherine; Davis, Scott (2004), "Genetic Contributions to Caribbean Iguana Conservation", Iguanas: Biology and Conservation, University of California Press, pp. 45–57, ISBN 978-0-520-23854-1
  3. 1 2 3 Blair, David (1991), "WEST INDIAN IGUANAS OF THE GENUS Cyclura Their Current Status in the Wild, Conservation Priorities and Efforts to Breed Them in Captivity" (PDF), Northern California Herpetological Society Special Publication, SE (6), pp. 55–56, archived from the original (PDF) on 2008-04-11
  4. ↑ Sanchez, Alejandro, "Family Iguanidae: Iguanas and Their Kin", Father Sanchez's Web Site of West Indian Natural History Diapsids I: Introduction; Lizards, Kingsnake.com, retrieved November 26, 2007
  5. ↑ "Cyclura: Harlan, 1825", Integrated Taxonomic Information System, 2001, retrieved 2007-10-07
  6. ↑ Schwartz, A.; Carey, M. (1977), "Systematics and evolution in the West Indian iguanid genus Cyclura.", Studies on the Fauna of Curaçao and Other Caribbean Islands, 173, pp. 15–97
  7. ↑ Frost, D.E. and R.E. Etheridge (1989) A Phylogenetic Analysis and Taxonomy of Iguanian Lizards (Reptilia: Squamata). Univ. Kansas Mus. Nat. Hist. Misc. Publ. 81
  8. ↑ Frost, D.R., R. Etheridge, D. Janies and T.A. Titus (2001) Total evidence, sequence alignment, evolution of Polychrotid lizards, and a reclassification of the Iguania (Squamata: Iguania). American Museum Novitates 3343: 38 pp.
  9. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Hollingsworth, Bradford D. (2004), "The Evolution of Iguanas: An Overview of Relationships and a Checklist of Species", Iguanas: Biology and Conservation, University of California Press, pp. 35–39, ISBN 978-0-520-23854-1
  10. ↑ Cyclura cychlura, The Reptile Database
  11. ↑ Burton, Frederic (2004), "Taxonomic Status of the Grand Cayman Blue Iguana" (PDF), Caribbean Journal of Science, Caribbean Journal of Science, 8 (1), pp. 198–203, retrieved 2007-09-16
  12. 1 2 Knapp, Charles R.; Hudson, Richard D. (2004), "Translocation Strategies as a Conservation Tool for West Indian Iguanas", Iguanas: Biology and Conservation, University of California Press, pp. 199–209, ISBN 978-0-520-23854-1
  13. ↑ Derr, Mark (2000-10-10), "In Caribbean, Endangered Iguanas Get Their Day", New York Times Science Section
  14. 1 2 3 4 Alberts, Allison; Lemm, Jeffrey; Grant, Tandora; Jackintell, Lori (2004), "Testing the Utility of Headstarting as a Conservation Strategy for West Indian Iguanas", Iguanas: Biology and Conservation, University of California Press, p. 210, ISBN 978-0-520-23854-1
  15. 1 2 3 Hazard, Lisa C. (2004), "Sodium and Potassium Secretion by Iguana Salt Glands", Iguanas: Biology and Conservation, University of California Press, pp. 84–85, 88, ISBN 978-0-520-23854-1
  16. ↑ Iverson, John; Smith, Geoffrey; Pieper, Lynne (2004), "Factors Affecting Long-Term Growth of the Allen Cays Rock Iguana in the Bahamas", Iguanas: Biology and Conservation, University of California Press, p. 184, ISBN 978-0-520-23854-1
  17. 1 2 3 4 Adams, Colette (May 26, 2004), "Obituary" (PDF), Iguana Specialist Group Newsletter, 7 (1): 2
  18. 1 2 3 4 5 6 7 De Vosjoli, Phillipe; David Blair (1992), The Green Iguana Manual, Escondido, California: Advanced Vivarium Systems, ISBN 1-882770-18-8
  19. ↑ Martins, Emilia P.; Lacy, Kathryn (2004), "Behavior and Ecology of Rock Iguanas,I: Evidence for an Appeasement Display", Iguanas: Biology and Conservation, University of California Press, pp. 98–108, ISBN 978-0-520-23854-1
  20. 1 2 3 4 5 6 7 Hudson, Richard D.; Alberts, Allison C. (2004), "The Role of Zoos in the Conservation of West Indian Iguanas", Iguanas: Biology and Conservation, University of California Press, pp. 274–289, ISBN 978-0-520-23854-1
  21. 1 2 3 Wyatt, III, John E. (2003), "Indianapolis Zoo Conducts Ricord's Iguana Field Research", Project Iguana, Indianapolis Zoo, archived from the original on 2008-02-06, retrieved 2007-10-04
  22. ↑ "Iguanas Hatch In Indianapolis" (PDF), Significant Efforts in Conservation, Association of Zoos and Aquariums, p. 39, 2002, retrieved 2007-10-04

Further reading

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