Overview

Brief Summary

Biology

The mating season of this rock iguana begins in May and continues into June, followed by nest digging from the end of June into July, and hatchlings emerge from nest-burrows in September or October (6). Both males and females have been observed mating with multiple partners, and a polygamous mating system is thought likely, although repeat matings with the same partner are also frequently observed (6). As a result of competition for access to females, some males may utilise forced-copulation and mate-guarding (6). Clutch size correlates to female body size, both of which are relatively small compared to other iguanas, and can vary between anything from two to ten eggs, depending on the subspecies and location (6). Nest defence by females appears to vary with nesting density (6), but males seem to be territorial throughout the year (4). Indeed, male Acklin's iguanas (C. r. nuchalis) have been observed chasing other males out of defended areas, and engaging in 'jousting matches' involving open-mouthed territorial displays, and individuals often bear bite-mark-like scars (4). This iguana primarily feeds on plant material of several species, but birds, conspecific hatchlings, the legs of dead land crab, a grasshopper, a hermit crab and insect material have also been recorded in the diet (6).
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Description

The San Salvador iguana is a strikingly handsome lizard, exhibiting an impressive crest of spiny scales down its back and a variable array of bright and beautiful colours (4). Varying between subspecies and indeed between individuals, the back can range from red, orange or yellow, to green, brown or grey, usually patterned by darker markings and fine vermiculations (4). The very brightest colours (red, orange or yellow) are normally only displayed by males, which are especially conspicuous at warmer body temperatures (4). Juveniles lack these bright colours, being solid brown or grey, usually with a slightly paler band in the middle of the back and faint longitudinal stripes (4). Body sizes of iguanas vary significantly from cay to cay, and seem to be positively correlated with the diversity of plant food available (1).
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Distribution

Continent: Caribbean
Distribution: Central Bahama Islands, including San Salvador, the Exuma Cays,  islands of the Crooked-Acklins group.  Cyclura rileyi rileyi: San Salvador I. and satellites.
Type locality: San Salvador Island, Bahama Islands.  Cyclura rileyi cristata (HOLOTYPE AMNH 7238): southern Exuma Cays.  Cyclura rileyi nuchalis (HOLOTYPE ANSP 11985): cays in Bight of Acklins.
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Range

The nominate subspecies, C. r. rileyi, was once found throughout the main island of San Salvador, but is now largely restricted to two cays (Guana and Pigeon) within the Great Lake, and four tiny offshore cays (Goulding, Green, Low, Manhead) (5) (6). In 2005, 10 individuals were also moved from Green Cay to Cut Cay off San Salvador Island, creating a new population (8). The White Cay iguana (C. r. cristata) is found only on a single island, White (Sandy) Cay, in the southern Exuma Islands of The Bahamas (1). Natural populations of Acklin's iguana (C. r. nuchalis) occur only on Fish Cay and North Cay in the Acklins Bight, Bahamas (1), but an introduced population also exists on a single island in the Exumas Land and Sea Park (6).
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Physical Description

Type Information

Paratype for Cyclura rileyi
Catalog Number: USNM 31971
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Watlings Island (= San Salvador Island), San Salvador Island, Bahamas
  • Paratype: Stejneger, L. 1903. Proc. Biol. Soc. Washington. 16: 130.
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Paratype for Cyclura rileyi
Catalog Number: USNM 31970
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Watlings Island (= San Salvador Island), San Salvador Island, Bahamas
  • Paratype: Stejneger, L. 1903. Proc. Biol. Soc. Washington. 16: 130.
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Paratype for Cyclura rileyi
Catalog Number: USNM 31966
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Watlings Island (= San Salvador Island), San Salvador Island, Bahamas
  • Paratype: Stejneger, L. 1903. Proc. Biol. Soc. Washington. 16: 130.
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Paratype for Cyclura rileyi
Catalog Number: USNM 31965
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Watlings Island (= San Salvador Island), San Salvador Island, Bahamas
  • Paratype: Stejneger, L. 1903. Proc. Biol. Soc. Washington. 16: 130.
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Holotype for Cyclura rileyi
Catalog Number: USNM 31969
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Watlings Island (= San Salvador Island), San Salvador Island, Bahamas
  • Holotype: Stejneger, L. 1903. Proc. Biol. Soc. Washington. 16: 130.
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Ecology

Habitat

Habitat and Ecology

Systems
  • Terrestrial
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A wide range of habitat is used, including coastal rock and limestone rocky outcrops, sand dunes, coastal coppice and blacklands coppice vegetation, and mangrove vegetation communities (1) (5). Like other rock iguanas (Cyclura spp.), San Salvador iguanas are thought to require loose soil or sandy areas for nest construction (1).
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Life History and Behavior

Life Expectancy

Lifespan, longevity, and ageing

Observations: Not much is known about the longevity of these animals, though they have been known to live 9.2 years (http://www.pondturtle.com/). Considering the longevity of similar species, however, maximum longevity could be significantly underestimated.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
C2a

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
Carter, R.L. & Hayes, W.K.

Reviewer/s

Contributor/s

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

Classified as Endangered (EN) on the IUCN Red List 2006 (1) and listed on Appendix I of CITES (3). Subspecies: the San Salvador iguana or San Salvador rock iguana (C. r. rileyi) and the White Cay iguana (C. r. cristata) are classified as Critically Endangered (CR), and Acklin's iguana or San Salvador rock iguana (C. r. nuchalis) is classified as Endangered (EN) on the IUCN Red List 2006 (1).
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Threats

Cyclura rileyi is amongst the most threatened of the West Indian rock iguanas, with two of its three recognised subspecies being listed as critically endangered by the IUCN, and the third as endangered (6). One of the most devastating impacts has been the large-scale habitat destruction by European and American colonialists, who cleared forests for conversion to agriculture, and introduced many non-native plants and animals (6). The San Salvador iguana now has a relatively remote distribution away from most human settlements, but a large and varied range of threats nevertheless continue to make their prospects of long-term survival tenuous (4) (7). The species is vulnerable to introduced predators and feral animals such as cats, dogs and rats, with rats recently discovered on Guana, Low, High, and Pigeon Cays, and juvenile iguanas noticeably scarce on Guana and Low Cays (4) (7). Habitat degradation is also a concern, with vegetation being damaged by catastrophic storms and hurricanes in the areas, as well as by the larvae of an introduced moth (Cactoblastis cactorum), which are devastating the prickly-pear cacti (Opuntia stricta), an important food source for iguanas on several cays (4) (7). Sadly, there are no known means of controlling the moth (4) (7). A mysterious 'die-off' also occurred on Guana Cay in spring 1994, possibly as the result of disease (4). However, it has also been suggested that mosquito control chemicals, which had recently been implemented to aid a growing tourism industry, could have been the culprit (4). Disease could potentially be catastrophic to many of the subpopulations due to their small and isolated nature (7). Small populations are also likely to suffer from the negative effects of inbreeding, diminishing their viability (4). A further threat to most, if not all, populations, is rising sea levels, which threaten to swamp much of the iguana's existing habitat in the future (6). An additional threat to the small population of White Cay iguanas (C. r. cristata) is the invasion of Australian pine trees (Casuarina), which have begun to dominate the vegetation on White Cay, attracting numerous birds of prey (falcons) during winter and migration (6). There is also evidence of illegal smuggling of the White Cay iguana (C. r. cristata), which probably poses the greatest threat to this subspecies, together with the possibility of introduced animals (4). Indeed, a raccoon discovered on White Cay apparently killed a significant proportion of the small iguana population, particularly juveniles and females (4), before it was removed in 1997 (6). Fortunately, the Acklin's iguana (C. r. nuchalis) populations seems to be fairly stable, although introduced hutia (Geocapromys ingrahami) on a neighbouring cay may be affecting the vegetation available to the subspecies, and the potential for illegal poaching remains a threat (4).
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Management

Conservation Actions

Conservation Actions
It is listed on CITES Appendix I.
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Conservation

Since a number of surrounding cays, as well as the mainland of San Salvador, have very similar habitat to that currently used by the species, reintroductions to parts of the iguana's former range are a viable and important focus of conservation efforts (4). An introduced population of Acklin's iguanas (C. r. nuchalis) currently thrives on an island within the Exumas Land and Sea Park (6), and a successful translocation of five adult pairs of C. r. rileyi from Green Cay to Cut Cay took place in February 2005, funded by a 2004 grant from the International Iguana Foundation (8). Candidate cays for further reintroductions (and source of animals) include Barn Cay (from Guana Cay), Cato Cay (from Green Cay), and High Cay (from Low Cay). Corrective actions may first be required to render each cay suitable for reintroduction (e.g., removal of feral rats), and reintroduction of iguanas on the mainland should be undertaken only if large areas are protected, particularly from the feral dogs and cats that are already numerous in local areas (4). There have also been efforts to remove invasive species and restore nesting habitat on a number of cays (6). Black rats were eradicated in 1998 on White Cay, and in 2000 on Low Cay, and virtually all of the extensive Casuarina on White Cay was cut down in 2005 (6). Two cays have also been identified as potential sites for the establishment of a second wild population of the critically endangered White Cay iguana (C. r. cristata) subspecies (4). Ardastra Gardens in Nassau (New Providence Island, Bahamas) currently holds two juveniles in captivity, and it has been argued that the development of a captive-breeding programme here could help benefit reintroduction attempts and the preservation of genetic diversity of small populations (4). It has also been suggested that captive head-starting programmes, which have been highly successful for other West Indian iguanas, could help survival rates of this rare species (6). Additionally, a public relations campaign will be critical to the conservation of this iguana, important both in raising awareness and concern among island residents for their threatened iguana, and in promoting the need for complete protection of the cays on which these beautifully colourful yet dangerously threatened iguanas live (4).
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Wikipedia

Cyclura rileyi

Cyclura rileyi, commonly known as the San Salvador rock iguana or Bahamian rock iguana, is a critically endangered species of lizard in the genus Cyclura native to three island groups in the Bahamas. The species is in decline due to habitat encroachment by human development and predation by feral dogs and cats. There are three subspecies: the Acklins ground iguana (Cyclura rileyi nuchalis), the White Cay iguana (Cyclura rileyi cristata) in addition to the nominal subspecies (Cyclura rileyi rileyi).

Taxonomy[edit]

The San Salvador rock iguana is an endangered species of lizard of the genus Cyclura from the family Iguanidae. First identified by Leonhard Hess Stejneger in 1902, they are known commonly in the Bahamas as iguanas.[2] Its generic name Cyclura, is derived from the Greek words cyclos meaning "circular" and urus meaning "tail", after the thick ringed tail characteristic of all Cyclura iguanas.[3] Its specific name, rileyi, is a Latinized form of the name of American biologist, Joseph Harvey Riley.[4]

As of 1975 two additional subspecific forms have been identified along with the nominal subspecies: the Acklins ground iguana (C. r. nuchalis) and the White Cay iguana (C. r. cristata).[2] Together they are one of the most threatened species of all the West Indian rock iguanas and are described as critically endangered according to the current IUCN Red List.[1]

Anatomy and morphology[edit]

Cyclura rileyi rileyi from Low Cay.

Measuring 300 to 390 mm (12 to 15 in) in length when full grown, the San Salvador rock iguana is a colorful lizard varying between subspecies as well as between individual specimens. The lizard's back color can range from red, orange or yellow, to green, brown or grey, usually patterned by darker markings. The very brightest colors (red, orange, blue, or yellow) are normally only displayed by males and are more pronounced which at warmer body temperatures. Immature iguanas lack these bright colors, being either solid brown or grey with faint slightly darker stripes.[1]

This subspecies, like other species of Cyclura, is 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.[5][6]

Distribution[edit]

Once inhabiting all the large islands of the Bahamas, today they are confined to 6 populations in small remote cays of three island groups: San Salvador Island, Acklins, and Exuma.[7] A study in 1995 estimated there were between 426 and 639 specimens left in the wild, and that this number has likely been reduced since much of their habitat was destroyed in 1999 by Hurricane Floyd.[8] The three island groups, each harboring its own subspecies, are on separate banks and were not connected during the last glacial period when water levels were 100 m (330 ft) lower than they are at present.[7]

Diet[edit]

Like all Cyclura species the San Salvador rock iguana is primarily herbivorous, 95% of which from consuming leaves, flowers and fruits from 7 different plant species such as seaside rock shrub (Rachicallis americana), and erect prickly pear (Opuntia stricta).[7] This diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds and fungi.

Mating[edit]

Female San Salvador rock iguanas attain sexual maturity when they reach 20 cm (7.9 in) in length from snout to vent and weigh 300 g (11 oz). Males appear to mature at a slightly larger size, at approximately seven years of age.[7]

Mating occurs in May and June, with clutches of 3-10 eggs usually laid in June or July, in nests excavated in pockets of earth exposed to the sun. Individuals are aggressively territorial from the age of about 3 months.

Conservation[edit]

While the island's natives often used iguanas as food and funerary offerings in pre-colonial times, man's largest-scale devastation to these animals was as a result of clear-cutting forests to create plantations as well as the introduction of non-native species.[1] Imported black rats, raccoons, feral dogs, mongoose, hogs, and cats have taken their toll on the population by direct predation, as has the larvae of a moth (Cactoblastis cactorum), introduced decades ago to the Caribbean, which are rapidly devastating prickly-pear cacti, an important food source for the iguanas.[1] The Guana Cay population has been reduced to less than 24 individual animals.[8]

Other threats by humans include tourists trampling iguanas' nests, iguanas contracting disease from eating human garbage, and illicit smuggling for the pet trade.[1] As development increases on the islands and further isolates populations, these animals will be threatened by lack of gene flow between the cays.[1]

As of August 2007, no legal captive breeding programs exist outside of the Bahamas.[1] The Bahamian government has refused to issue export permits for any rock iguanas.[1] However, Ardastra Gardens in Nassau (New Providence Island, Bahamas) currently holds two juveniles and plans to implement a captive breeding program.[1] A public relations campaign is planned to heighten awareness and appreciation among island residents for this endemic lizard.[1]

References[edit]

  1. ^ a b c d e f g h i j k Carter, R.L. & Hayes, W.K. (1996). "Cyclura rileyi". IUCN Red List of Threatened Species. Version 2009.1. International Union for Conservation of Nature. Retrieved December 5, 2009. 
  2. ^ a b Hollingsworth, Bradford D. (2004), "The Evolution of Iguanas: An Overview of Relationships and a Checklist od Species", Iguanas: Biology and Conservation (University of California Press): 38–39, ISBN 978-0-520-23854-1 
  3. ^ Sanchez, Alejandro (November 26, 2007), Father Sanchez's Web Site of West Indian Natural History Diapsids I: Introduction; Lizards 
  4. ^ "Riley, Joseph - Biography". Washington Biologists' Field Club; Patuxent Wildlife Research Center. 
  5. ^ De Vosjoli, Phillipe; David Blair (1992), The Green Iguana Manual, Escondido, California: Advanced Vivarium Systems, ISBN 1-882770-18-8 
  6. ^ 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): 98–108, ISBN 978-0-520-23854-1 
  7. ^ a b c d Hayes, William; Carter, Ronald; Cyril, Samuel; Thornton, Benjamin (2004), "Conservation of a Bahamian Rock Iguana, I", Iguanas: Biology and Conservation (University of California Press): 232–243, ISBN 978-0-520-23854-1 
  8. ^ a b Hayes, William K. (2003). Can San Salvador’s Iguanas and Seabirds Be Saved?. Department of Natural Sciences, Loma Linda University. 
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