Cyclura rileyi

The San Salvador rock iguana or Bahamian rock iguana (Cyclura rileyi ) is a critically endangered species of lizard of 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. Taxonomically the species is composed of three subspecies the Acklin's Ground Iguana (Cyclura rileyi nuchalis), the White Cay Iguana (Cyclura rileyi cristata) and the nominal species the San Salvador Iguana (Cyclura rileyi rileyi).

Taxonomy

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. 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. Its specific name,rileyi, is a Latinized form of the name of American biologist, Joseph Harvey Riley.

As of 1975 two additional subspecific forms have been identified along with the nominal species: the Acklin's Ground Iguana(Cyclura rileyi nuchalis) and the White Cay Iguana (Cyclura rileyi cristata). 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.

Anatomy and morphology

Measuring 300mm to 390mm 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.

Males of this subspecies, like other species within the Genus Cyclura are larger than females and have more prominent dorsal crests in addition to femoral pores on their thighs, which are used to release pheromones; females lack these pores and have shorter crests than the males making the animals sexually dimorphic.

Distribution

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.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. The three island groups, each harboring its own subspecies, are on separate banks and were not connected during the last ice age when water levels were 100m lower than they are at present.

Diet

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 wild thyme and prickly pear cactus(Opuntia stricta). This diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds and fungi.

Mating

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

Causes of decline

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 introduce plantations as well as the introduction of non-native species. 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 West Indies, which are rapidly devastating prickly-pear cacti, an important food source for the iguanas. The Guana Cay population has been reduced to less than 24 individual animals.

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

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

References

External links

• Entry at Cyclura.com
• Iguana Specialist Group: San Salvador Iguana
• International Iguana Foundation - San Salvador Iguana