Cyclura

Diversity

The Genus Cyclura contains 11 recognized species. Since a taxonomic review of Cyclura in 1977, five of the described subspecies were promoted to species (Schwartz and Carey, 1977). There are 8 recognized subspecies in the species Cyclura cychlura , Cyclura nubila , and Cyclura rileyi . All Cyclura species are on the IUCN Red List of Threatened Species. Four species are critically endangered, three are endangered, three are vulnerable and one is extinct. Cyclura species are located on islands in the West Indies, where they are the largest surviving native land vertebrate. Cyclura species are primarily herbivorous, though they will eat animal matter that is easy to obtain such as such as insects, land crabs, and rotting flesh. As iguanas are good climbers, it is not uncommon to find them in trees. Rock iguanas have no known natural predators, although feral domestic animals are now one of the largest threats to these iguanas. This is due to predation by feral animals or competition for resources with them. (Blair, 2000)

Geographic Range

All populations of rock iguanas are endemic to the islands of the West Indies. They are spread widely throughout the islands, with no specific island as a hotspot (Blair, 2000).

• Biogeographic Regions
• neotropical neotropical
  • introduced introduced
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Rock iguanas are found in xerophytic scrub forests, sandy areas, and mangrove forests on islands in the West Indies (Beovides-Casas and Mancina, 2006). They use caves and crevices that had been formed in heavily eroded limestone as retreats and will sometimes dig burrows in sandy areas. Adults are mostly terrestrial while young can often be found in trees (Blair, 2000).

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• forest forest
• scrub forest scrub forest

Systematic and Taxonomic History

Cyclura is in the family Iguanidae. Harlan first described the genus Cyclura in 1824 (Buckley et al., 2016). Since then, other have used Metapoceros and Aloponotus to describe C. cornuta , and C. ricordii respectively. These names are now synonyms because we recognize all of the species as Cyclura species (Schwartz and Carey, 1977). Currently there are 11 recognized species, several of which have been elevated from subspecies level to species level. One of the first reviews was in 1916, and described 11 species and no subspecies. Most of the names used in the review are now synonyms due to name changes and taxonomic level changes (Barbour and Noble, 1916). Later in 1977, another review was published in which 8 species were recognized. Some of the species included subspecies (Schwartz and Carey, 1977). In the most recent review, 11 species are recognized and 16 “forms,” including species and subspecies (Buckley et. al., 2016).

Physical Description

The genus Cyclura is a group of large, island endemic iguanas that have thick, ringed tails. Males are larger than females with larger dorsal crest scales, femoral pores, and bodies. In general, males are 263 to 745 mm snout-vent length (SVL) and females are 240 to 623 mm snout-vent length. Body size is the most sexually dimorphic trait in Cyclura species (Blair, 2000). The most reliable method of differentiating different species is by using scale counts and patterns because most of the species have base pigmentations of blacks, greys, or browns (Schwartz and Carey, 1977). Each species often has different coloration of dorsal scales, head, and legs. Juveniles are often grey with a number of dark crossbars or chevrons that span the length of the back. These patterns fade or disappear with age and maturity (Alberts and Lemm, 2012).

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Since Cyclura is such an endangered genus, most research has been on these iguanas in captivity. In the wild, rock iguanas are mostly polygamous, but there are instances that have been recorded where they are promiscuous or monogamous (Blair, 2000). Rock iguanas are territorially aggressive and solitary until mating season. During mating season, males expand their territories to overlap with as many females as possible and will attack other males that enter their territory to monopolize females. Smaller males normally flee while chased by larger individuals. Physical fights are uncommon and generally only occur between similar sized individuals. Fights that do occur are vicious. Wounds that can result from fights include internal hemorrhaging, flesh wounds, tearing of the skin, in some cases death (Hunsaker II and Burrage, 1969). Females are also aggressive toward each other and will determine a hierarchy.

Copulation begins with a series of head bobs from the male toward the female, after which the male will position himself behind the female. He then will grasp the female on the nape of the neck attempting to restrain her to position himself for intromission. This process takes about 30 to 90 seconds but rarely any longer (Blair, 2000).

• Mating System
• monogamous monogamous
• polygynous polygynous
• polygynandrous (promiscuous) polygynandrous (promiscuous)

The breeding season of Cyclura species is generally from April to June. Oviposition occurs approximately 40 days later, from June to July. Clutch size varies with size and age of the female. Smaller females can lay 2 to 6 eggs while larger females can lay up to 23 eggs. Eggs are laid in a dug-out nesting burrow. Incubation lasts for 65 to 90 days, after which hatchlings can take up to two weeks to dig out of a nest chamber and emerge. Sexual maturity is sometimes reached at younger ages in captivity than in the wild, but will generally occur between 2 to 9 years of age (Blair, 2000). Cyclura species normally only mate once a year, though one case has been reported to have mated and nested twice, suggesting that biannual reproduction may be possible, but is a rare occurrence (Burton, 2004).

• Key Reproductive Features
• seasonal breeding seasonal breeding
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Before fertilization, females increase food intake and body temperature to reach optimal metabolic rates to make eggs. During copulation, the female will often end up with injuries to the nuchal crest or other parts of her body if the male is overly aggressive. After copulation, the male is no longer involved in the parenting process. Several days before oviposition, females will go outside their normal ranges to find a suitable place to dig a nesting burrow. These burrows are deep, spacious (ranging from 0.4 meters to 1.5 meters long), and warm (29.4 to 30.6 °C) (Blair, 2000). In captivity, nesting is the biggest hurdle in successful breeding. If the nest is not dug properly or the female holds onto the eggs for too long because the nest is not to the female’s liking, the eggs will not hatch. If the female is satisfied she will then cover the nest and often protect it from predators for up to several weeks. Once the eggs hatch, the hatchlings are independent and go on to live solitary lives. Sadly, in the wild juvenile Cyclura species experience high mortality rates that can reach nearly 100% in some populations due to natural predators as well as introduced predators (Alberts and Lemm, 2012; Blair, 2000).

• Parental Investment
• no parental involvement
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Cyclura contains some of the longest living lizard species. It is estimated that these lizards can live 25 to 40 years in the wild (Blair, 2000). Captive members have been known to exceed that range because of the high level of maintenance provided in captivity. The longest living member of Cyclura on record is a male member of the species Cyclura lewisi named Godzilla, having lived to 69 years of age in the Gladys Porter Zoo in Texas. Survival rates are lowest for juveniles due to predation by natural predators such as snakes and birds, as well as introduced predators such as feral cats and dogs. These rates can range from 22 to 97% depending on both the population and its location. Generally, chances of survival increase with increase in size and maturity (Alberts and Lemm, 2012).

Behavior

Rock Iguanas are diurnal, sedentary, and solitary lizards that generally only interact during mating. Many intraspecific behaviors are demonstrated during mating. Outside of mating season, both males and females establish dominance hierarchies. In males, dominance is associated with size of the head and body, display behaviors, testosterone levels, territory size, and proximity to females. In females, dominance is mostly associated with size (Alberts et al., 2002). Dominant individuals may attack any intruders in their territory after warning them with a series of head bobs. Cyclura species are independent and solitary as soon as they hatch. Hatchlings will often spend the first few months of their lives living in the trees to avoid ground predators but will still sometimes fall prey to birds and snakes. When rock iguanas are active, their time is primarily spent foraging, traveling as far as 300 to 500 meters to reach certain forests to feed in (Alberts and Lemm, 2012).

• Key Behaviors
• arboreal arboreal
• terricolous
• diurnal diurnal
• sedentary sedentary
• solitary solitary
• territorial territorial
• dominance hierarchies dominance hierarchies

Communication and Perception

Rock iguanas use both chemical and visual communication when interacting with other rock iguanas and more specifically each species. These iguanas excrete a protein/lipid mixture from their femoral pores that is used for attracting mates as well as marking territory. They use both their tongue and their Jacobson’s organ for chemoreception of different scent markers from pheromones, or even from scat of conspecifics. The most important visual signal used in rock iguanas is the head bob, which is a when the head is raised then lowered in a species-specific pattern. The head bob is used in territorial maintenance and in mating. It is often the first warning intruders or predators will get before any kind of aggression occurs. Another form of visual signaling is body posturing. Body posturing is used in both aggressive encounters and submissive displays. In aggressive encounters, large males will turn their bodies sideways, stand high on their feet and inflate their bodies with air to appear as large as possible. In submissive displays, females or small males will drop their bodies as close to the ground as possible with the base of the tail raised. These visual signals are a good indication of the dominance hierarchy (Alberts and Lemm, 2012).

• Communication Channels
• visual visual
• chemical chemical

• Other Communication Modes
• pheromones pheromones
• scent marks scent marks

• Perception Channels
• visual visual
• chemical chemical

Food Habits

Rock iguanas are primarily herbivorous. Their diet includes flowers, fruit, stems and leaves of plants from around 105 endemic plant species of the West Indies. They also opportunistically consume animal matter. This includes carrion, insects, land crabs, and skin flakes and feces of conspecifics (Alberts and Lemm, 2012; Pasachnik and Martin-Velez, 2017).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • scavenger scavenger
• herbivore herbivore
  • folivore folivore
  • frugivore frugivore
• omnivore omnivore

Predation

Since adult rock iguanas are the largest land vertebrates on their islands, they have few natural predators. However, hatchling and juvenile iguanas have quite a few predators. Natural predators for young rock iguanas include birds, snakes, and in one recorded instance, barracuda. Introduced species are the biggest threat to Cyclura species. Dogs, cats, and mongooses prey heavily on rock iguanas and have caused extinctions of some populations. Other introduced species, such as pigs, raccoons, rats, and mice also eat eggs, kill hatchlings and adults, and destroy habitat. When confronted by predators, rock iguanas exhibit a fight or flight response. They use aggression signals like head bobs or body inflation to scare away predators and will charge if cornered. Humans also historically hunted rock iguanas as a food source (Alberts and Lemm, 2012; Blair, 2000).

Ecosystem Roles

Rock iguanas are seed dispersers for native plants (Alberts and Lemm, 2012).

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Cyclura species were once an important food source for natives of the West Indies and are illegally hunted in some places to this day. They also are flagship species of the West Indies that promote ecotourism (Blair, 2000; Alberts and Lemm, 2012).

• Positive Impacts
• food food
• ecotourism ecotourism

Economic Importance for Humans: Negative

Rock iguanas have been known to raid gardens or farms to eat vegetation, but is so rare that economic impact of this is negligible. Cyclura species pose no physical threat to humans unless provoked (Alberts and Lemm, 2012).

• Negative Impacts
• crop pest

Conservation Status

Species in the genus Cyclura are some of the most endangered lizard species in the world. Of the 16 currently recognized species and subspecies, 5 are endangered and 8 are critically endangered, according to the IUCN Red List of Threatened Species. The decline in Cyclura species is directly related to European settlement of the West Indies. As human populations increased, habitat loss and degradation increased dramatically. This is due to human expansion and the introduction of feral livestock on the islands. Increases in the industries of limestone mining, agriculture, timber extraction and land clearing for tourist resorts and housing developments have reduced natural habitats to mere fractions of pre-settlement sizes (Alberts and Lemm, 2012).

Domestic and commensal animals that settlers brought with them have also had devastating impacts on rock iguana populations. Feral and domestic livestock, including goats, burros, donkeys, sheep, and cattle, compete with rock iguanas for food, alter local vegetation composition, prevent regeneration of plants and even trample on nests and burrows causing collapse of nests or compaction of soils to the point at which they are no longer suitable for nesting (Alberts and Lemm, 2012).

Predation on rock iguanas by introduced domestic and commensal animals is also a significant threat. Having evolved with no natural predators, the introduction of feral cats, dogs, pigs, mongooses, and rats has devastated rock iguana populations. Dogs are capable of killing and consuming adults of even the largest species. Although cats are more likely to prey on hatchlings and juveniles, cats can kill all age classes of some of the smaller species. Pigs and rats have less destructive effects on adult iguanas, they have devastating effects on nests by feeding on eggs (Alberts and Lemm, 2012).

Direct human interaction with rock iguanas has had negative effects on iguana populations. Illegal hunting and poaching is less severe than habitat loss and predation by introduced animals, but still has drastic results. Interaction with tourists is even less severe, but still a problem. Tourists walking through nesting areas can collapse nesting chambers. An emerging threat is tourists feeding iguanas inappropriate food items. This not only leads to increased intraspecific aggression and disruption of natural social systems, but can lead to dietary shifts that can result in medical consequences. Human presence with the iguanas is also making the iguanas less wary of humans. This loss of wariness makes hunting and poaching easier. With increased tourism and human population growth, more iguanas are killed due to vehicular traffic on roads (Alberts and Lemm 2012; Hines, 2011).

Numerous conservation programs are in place to protect these endangered lizards. Habitat protection through the establishment of both protected areas and parks is a means to prevent further habitat loss. This includes restricting access to beaches and forests where rock iguanas live. Another action that is being taken is to control populations of invasive mammals. Efforts are being made to trap and eradicate feral pigs, cats, dog, rats, and mongooses. Some of the conservation actions are specifically focused in increasing population sizes. One action is called headstarting. This is when eggs laid in the wild are collected and brought to safe facilities. There, the hatchlings are raised until they are large enough to fend for themselves, and released back to where they were collected, giving them a “head start” in the race against predators. Another action is the introduction of translocation programs. These programs move groups of iguanas to unoccupied habitats. This is especially effective for populations that are restricted to small areas and in turn vulnerable to extinction events (Alberts and Lemm, 2012).

Other Comments

The name Cyclura is derived from Greek and literally means “circular tail” (“cyclos” + “urus”), after the thick-ringed tail characteristics that all members of Cyclura have (Alberts and Lemm, 2012). The bones of Cyclura have been found in caves and Indian kitchen middens on numerous islands that they can no longer be found on including Saint Thomas, New Providence, Great Exuma and Puerto Rico (Blair, 2000).

Additional Links

Encyclopedia of Life

Contributors

Riley Magidow (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Alberts, A., J. Lemm, A. Perry, L. Morici, J. Phillips. 2002. Temporary alteration of local social structure in a threatened population of Cuban iguanas (Cyclura nubila). Behavioral Ecology and Sociobiology , Vol. 55 Iss. 4: 324-335. Accessed February 05, 2018 at http://apps.webofknowledge.com.ezproxy2.library.colostate.edu/full_record.do?product=WOS&search_mode=GeneralSearch&qid=4&SID=6BDnSOhW8fd1ndWOOqj&page=1&doc=7 .

Alberts, A., J. Lemm. 2012. Cyclura : Natural History, Husbandry, and Conservation of West Indian Rock Iguanas . SAN DIEGO, CA: ELSEVIER ACADEMIC PRESS INC. Accessed February 27, 2018 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/B9781437735161100019 .

Barbour, T., G. Noble. 1916. A revision of the lizards of the genus Cyclura. Bulletin of the Museum of Comparative Zoology at Harvard College , 60: 139-302s. Accessed March 15, 2018 at https://biodiversitylibrary.org/page/30207456 .

Beovides-Casas, K., C. Mancina. 2006. Natural history and morphometry of the Cuban iguana (Cyclura nubila Gray, 1831) in Cayo Siju, Cuba. Animal Biodiversity and Conservation , Vol. 29 Iss. 1: 1-8. Accessed February 05, 2018 at https://search-proquest-com.ezproxy2.library.colostate.edu/docview/13231022?accountid=10223 .

Blair, D. 2000. "West Indian iguanas of the genus Cyclura: their current status in the wild, conservation priorities, and efforts to breed them in captivity" (On-line pdf). Accessed February 14, 2018 at http://www.vipersgarden.at/PDF/DB_Cyclura.pdf .

Buckley, L., K. Queiroz, T. Grant, B. Hollingsworth, J. Iverson, S. Pasachnik, C. Stephen. 2016. A checklist of the iguanas of the world (Iguanidae; Iguaninae). Herpetological Conservation and Biology , Vol. 11 Iss. 6: 4-46. Accessed March 09, 2018 at http://www.herpconbio.org/Volume_11/Monograph_6/2-Iguana_Taxonomy_Working_Group_2016.pdf .

Burton, F. 2004. Cyclura nubila lewisi (Grand Cayman blue rock iguana). Reproduction. Herpetological Review , Vol. 35 Iss. 4: 388-389.

Hines, K. 2011. Effects of ecotourism on endangered northern Bahamian rock iguanas ( Cyclura cychlura ). Herpetological Conservation and Biology , Vol. 6 Iss. 2: 250–259. Accessed February 28, 2018 at http://www.kirstennaturetravel.com/wp-content/uploads/2013/03/Hines_2011_herpconbio.pdf .

Hunsaker II, D., B. Burrage. 1969. The Significance of Interspecific Social Dominance in Iguanid Lizards. The American Midland Naturalist , Vol. 81 Iss. 2: 500-511. Accessed March 02, 2018 at https://www.jstor.org/stable/2423985?seq=2#page_scan_tab_contents .

Pasachnik, S., V. Martin-Velez. 2017. An evaluation of the diet of Cyclura iguanas in the Dominican Republic. Herpetological Bulletin , Vol. 140: 6-12. Accessed March 17, 2018 at https://search-proquest-com.ezproxy2.library.colostate.edu/zoologicalrecord/docview/1932787561/9D65A9EDCBFA4777PQ/3?accountid=10223 .

Schwarts, A., M. Carey. 1977. Systematics and evolution in the West Indian iguanid genus Cyclura. Studies on the Fauna of Curacao and Other Caribbean Islands , Vol. 53 Iss. 1: 15-97. Accessed February 24, 2018 at http://www.repository.naturalis.nl/document/549904 .