Cyclura nubila ssp. caymanensis
| Kingdom |
Phylum |
Class |
Order |
Family |
| ANIMALIA |
CHORDATA |
REPTILIA |
SQUAMATA |
IGUANIDAE |
| Scientific Name: |
Cyclura nubila ssp. caymanensis |
| Infra-specific Authority: |
Barbour & Noble, 1916 |
Common Name/s:
| English |
– |
Lesser Caymans Rock Iguana, Cayman Island Ground Iguana, Lesser Caymans Iguana |
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| Taxonomic Notes: |
Synonyms = Cyclura caymanensis Barbour & Noble 1916; Cyclura macleayi caymanensis Grant 1940; Cyclura nubila caymanensis Schwartz & Thomas 1975; Cyclura nubila caymanensis Schwartz & Carey 1977. |
Assessment Information
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| Red List Category & Criteria: |
Critically Endangered
B1+2abcde
ver 2.3
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| Year Assessed: |
1996 |
| Annotations: |
Needs updating
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| Assessor/s: |
Gerber, G. |
| Reviewer/s: |
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Geographic Range
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| Range Description: |
The Lesser Caymans iguana is native to two islands: Cayman Brac (38 km²) and Little Cayman (28.5 km²). The islands are 7.5 km apart and are well isolated from other land masses. Both islands have been continually inhabited since the early 1800s. Current human populations for Cayman Brac and Little Cayman are approximately 1,000 and 200 respectively.
In 1938 iguanas were abundant on Cayman Brac and Little Cayman. Since that time, populations of Lesser Caymans iguanas have declined and are clearly in danger of extinction, particularly on Cayman Brac. In 1965 the iguanas were abundant on Cayman Brac only along a relatively small section of the southwest coastline (Carey 1966). Today, the subspecies is nearly extinct on Cayman Brac. Over the last four years, F. Burton (pers. comm.) has seen only two iguanas on Cayman Brac (both juveniles) and received only two reports of sightings (both adults). Based on these results, the population probably numbers fewer than 50 individuals.
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| Countries: |
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Population
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| Population: |
Presently Little Cayman still supports a widely, although patchily, distributed iguana population (G. Gerber unpubl. data). The population is reproducing and all age classes are represented, although juvenile mortality is very high due to predation by feral cats. During nine months of field work on Little Cayman in 1993 over 200 iguanas were captured and marked. However due to the inaccessibility of much of the interior of the island and the patchy distribution of iguanas, good population estimates are not available; mature iguanas possibly number between 750 and 1,500. he population appears not to have declined significantly since the 1970s (Townson 1980, Stoddart 1980) and 1980s (Blair 1983) and may even be larger today. Nonetheless, dense concentrations of iguanas which occupied the mid-northern (B. Ryan, pers. comm.) and mid-southern (Grant 1940) coasts of Little Cayman 50+ years ago no longer exist, and a growing population of feral cats and increasing human development severely threaten the long-term survival of iguanas on Little Cayman.
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| Population Trend: |
Unknown
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Habitat and Ecology
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| Habitat and Ecology: |
Like other rock iguanas, Lesser Caymans iguanas require suitable forage plants, basking areas, retreats and nesting sites. On Little Cayman these requirements are met in a variety of coastal and interior habitats and iguanas are widely dispersed. Maximum densities occur in dry evergreen bushlands and thickets growing on exposed and highly weathered limestone or dolomite. These habitats provide a diverse assemblage of forage plants, a mosaic of sun and shade for thermoregulation, and an abundance of solution holes in the rock substrate which iguanas of all sizes use as retreats. However, suitable nesting sites in these habitats are restricted to shallow patches of soil that accumulate in small depressions. Consequently many females migrate to coastal areas with relatively deep sandy soils to nest.
The diet of all age classes consists almost entirely of leaves, flowers and fruits; however, iguanas occasionally scavenge on animal carcasses (e.g., land crabs) or prey on slow-moving insects (e.g., Lepidopteran larvae).
Courtship and mating occur in April and early May, coinciding with the end of the dry season when temperatures and photoperiod are increasing. Males compete intensely for territories which are occupied in all seasons. Male territories are large, on the order of 1 ha, and during the breeding season as many as 10 females may temporarily reside within a single territory. The adult sex ratio appears to be skewed toward females.
Females lay a single clutch of 7-25 eggs (mean 15) annually, between late-May and mid-June, coinciding with the beginning of the wet season. Females nest either in small soil patches within the rocky interior or in large sandy tracts along the coast, and may migrate considerable distances to nest sites. Hatchling emergence occurs from early August to early September and incubation averages 72 days (range 63-80).
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| Systems: |
Terrestrial |
| Major Threat(s): |
Threats to Lesser Caymans iguanas include habitat destruction from road construction; commercial and residential real estate development; livestock grazing (on Cayman Brac) and farming practices; predation by feral cats and domestic dogs (and possibly introduced rats); disturbance of sensitive nesting areas; and road kills. Since the construction of a municipal power generating station on Little Cayman in the early 1990s habitat destruction associated with road construction and real estate development have increased dramatically and the human population, although still small, has increased several fold. Under the present socioeconomic conditions this pattern can be expected to accelerate. Plans to replace the existing, grass airstrip on Little Cayman with a new, paved airstrip are underway. Proposed sites for this project overlap areas of prime iguana habitat on the west end of the island. Aside from the loss of habitat, such an airstrip will significantly increase human visitation to the island and promote further development. The continued destruction and disturbance of coastal nesting areas on Little Cayman is of particular concern as nesting opportunities for iguanas in the interior appear to be limiting due to the paucity of suitable soil patches. Also the increasing number of feral cats on Little Cayman pose an immediate threat to population recruitment.
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Conservation Actions
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| Conservation Actions: |
Iguanas are protected within the Cayman Islands by the Animals Law of 1976 (Davies 1994) but protection of native habitats is lacking. The Development and Planning Law of 1971 provides a legal mechanism to prevent the destruction of terrestrial habitats in the Cayman Islands, but this has never been implemented (Davies 1994). Currently, the only protected areas on Cayman Brac and Little Cayman are the Cayman Brac Parrot Preserve (a 65 ha tract of potentially important iguana habitat) and the Little Cayman Ramsar Site (an 82 ha preserve encompassing Booby Pond and surrounding mangroves).
The National Trust for the Cayman Islands has had an active iguana conservation program since 1990. However, due to limited resources, efforts have largely concentrated on the Grand Cayman iguana. An intensive field study of Lesser Caymans iguanas was conducted on Little Cayman in 1993 by Gerber. Plans to continue this research await further funding.
A captive breeding program does not exist for this subspecies but may be warranted for the Cayman Brac population if it is genetically distinct from the Little Cayman population. This possibility needs to be investigated. No pure Lesser Caymans iguanas are presently held in zoological institutions (B. Christie pers. comm.).
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