This species will bite or scratch and strike with its tail if provoked or attacked, but is otherwise harmless and in no way detrimental to humans.
The skin color of C. cornuta allows it to blend in with its environment. This species also exhibits behaviors which are thought to deter predators as well as competitors. As discussed above, these include elaborate head and neck movements intended to make the lizard look larger and more fierce. These defenses don't work very well against introduced predators.
Known Predators:
The skin of C. cornuta has rough epidermal scales and is grayish brown or olive in color. The species is definitively identied by the large size of certain scales on the head, but few other iguana species are as large or have the "horns" (actually enlarged scales) on their heads. These horns are the source for the name for of the species. Males are larger than females and have relatively larger horns as well (Hamlett 2002, Cyclura.com 2002).
Range mass: 28.6 to 48.4 kg.
Range length: 60.96 to 121.92 cm.
Average length: 91.30 cm.
Other Physical Features: bilateral symmetry
Very little has been published regarding the longevity of this species because it is difficult to monitor in the wild. A life of 20 years in captivity is reported (Hamlett 2002), and some researchers predict that these animals may live decades long than that in the wild (Kaplan 2002, citing Blair).
Range lifespan
Status: captivity: 20 (high) years.
Average lifespan
Sex: male
Status: captivity: 16.7 years.
The natural habitat of C. cornuta is typically described as dry forest, scrub, or desert. This biome receives very little rain annually and the plants and animals which occupy it reflect the sun-drenched, arid environment. Mostly small trees and shrubs, cacti, and mesquite may surround the burrows that C. cornuta inhabits. Iguanas exhibit a considerable amount of plasticity in their habitat selection and C. cornuta is no exception. This species is primarily found near coastlines, however, human expansion has forced many populations to retreat further inland. This species requires warm temperatures and lots of solar radiation. Cyclura cornuta is typically found in regions where the annual mean temperature is at least 27 degrees Celsius. It has been displaced from much of its original range on Hispaniola by habitat destruction and introduced predators (Hamlett 2002, Cyclura.com 2002)
Range elevation: l (low) m.
Habitat Regions: tropical
Terrestrial Biomes: desert or dune ; forest ; scrub forest
Cyclura cornuta is found only on the island of Hispaniola in the Caribbean Sea (Hamlett 2002). A closely related species or subspecies (scientific opinions vary) was found on Navassa Island, but is now believed extinct. There is a living subspecies on Mona Island, near Puerto Rico.
Biogeographic Regions: neotropical (Native )
Other Geographic Terms: island endemic
Members of C. cornuta have a variable diet both seasonally and ontogenetically. Rhinoceros iguanas are mainly herbivores, eating a wide variety of leaves, fruits, flowers, and seeds. They occasionally eat animal food, mainly insects, land crabs, or carrion (especially dead birds and fish). Young iguanas in particular may take insects and other small animals. Iguanas that locate a food source (e.g. a fruiting bush) will actively defend it from conspecifics (Animal Network).
Animal Foods: carrion ; insects; terrestrial non-insect arthropods
Plant Foods: leaves; seeds, grains, and nuts; fruit; flowers
Primary Diet: herbivore (Folivore , Frugivore , Granivore )
Cyclura cornuta has been documented to feed on fruits. Because most seeds are difficult to digest without special bacteria, they often remain intact and end up in the animal's feces. This helps to both spread the seed and to fertilize it. C. cornuta therefore is crucial in communities in which it is the dominant frugivore.
Ecosystem Impact: disperses seeds
Rhinoceros iguanas are sometimes kept as pets, and in the past have been used as food. Currently they are not of great economic importance.
Positive Impacts: pet trade ; food
These iguanas hatch from eggs and are independent after hatching. They mature at 5 to 9 years of age (Cyclura.com 2002).
C. cornuta is threatened by human encroachment on and destruction of its natural habitat. The demand for old growth trees by the logging industry, limestone mining, pollution, predation, and wild fires have depleted the habitat and often forced this and many other species to migrate and/or go extinct. Haiti, a country mired in poverty, in particular has experienced a dramatic reduction in population due to poachers killing for food (Hamlett 2002). This species is listed as Vulnerable by the International Union for the Conservation of Nature, and is listed in Appendix I of CITES. This means that international trade in this species is generally forbidden with out strict permits from both exporting and importing countries. The closely related species/subspecies, C. cornuta stegneri, the Mona Island Ground Lizard, is considered Threatened by the U.S. Fish and Wildlife Department and protected under the Endangered Species Act.
US Federal List: threatened
CITES: appendix i
IUCN Red List of Threatened Species: vulnerable
There is legal trade in captive-bred rhinoceros iguanas. Potential purchasers should always insist on full documentation to ensure that they are not getting illegally collected wild animals. Illegal collection endangers the species, and is bad for the pet trade, as wild animals often carry parasites and diseases that have been eliminated from captive-bred populations.
Evidence for a polygynous mating system with social rank determining matings has been published. This corresponds to the fact that C. cornuta appears to be extremely territorial and males especially will attempt to dominate and intimidate conspecifics with head movements and body gyrations. They use similar motions to attract females, and may also use these head bobs and nods to scare away predators (Hunsaker II, et al. 1969).
Mating System: polygynous
The beginning of the mating season is late May, and C. cornuta is oviparous, so eggs are laid about 40 days after mating, usually in early August. Females dig burrows up to a meter and a half long in which to incubate the eggs and must keep them at a minimum of 30 degrees Celsius. Clutch size is extremely variable and may range from 5 to 20 eggs. Resource competition and/ or abundance of predators is thought to account for variations in egg-laying behavior(Hunsaker II, et al. 1969).
Breeding season: late May to early June
Range number of offspring: 5 to 20.
Average number of offspring: 10.
Range gestation period: 4 to 5 months.
Range age at sexual or reproductive maturity (female): 5 to 9 years.
Range age at sexual or reproductive maturity (male): 5 to 9 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; fertilization (Internal ); oviparous
There is no male parental care this species. Once females have laid their eggs, they sometimes guard the nest for a few weeks to prevent egg predation (D. Blair at Cyclura Research Information Collection).
Parental Investment: no parental involvement; female parental care
The rhinoceros iguana (Cyclura cornuta) is an endangered species of iguana that is endemic to the Caribbean island of Hispaniola (shared by Haiti and the Dominican Republic) and its surrounding islands. A large lizard, they vary in length from 60 to 136 centimetres (24 to 54 in), and skin colours range from a steely grey to a dark green and even brown. Their name derives from the bony-plated pseudo-horn or outgrowth which resembles the horn of a rhinoceros on the iguana's snout. It is known to coexist with the Ricord's iguana (C. ricordii); the two species are the only taxa of rock iguana to do so.
The rhinoceros iguana is a species of lizard belonging to the genus Cyclura. The rhinoceros iguana's specific name, cornuta, is the feminine form of the Latin adjective cornutus, meaning "horned" and refers to the horned projections on the snouts of males of the species. The species was first identified by Pierre Joseph Bonnaterre in 1789.[1][3]
In addition to the nominate race (C. c. cornuta) found on Hispaniola, the other subspecies is the extinct Navassa Island iguana (C. c. onchiopsis).[3][4] The Mona ground iguana (Cyclura stejnegeri) from Puerto Rico was originally thought to be a subspecies (and still is by some taxonomists), as Cyclura cornuta stejnegeri.
The rhinoceros iguana, like other members of the genus Cyclura, is a large-bodied, heavy-headed lizard with strong legs and a vertically flattened tail.[5] A crest of pointed horned scales extends from the nape of their neck to the tip of their tail.[5] Their color is a uniform gray to brown drab.[5] Most adults weigh 4.56 to 9 kilograms (10.1 to 19.8 lb).[6] Like all reptiles, rhinoceros iguanas are cold-blooded, meaning they need external sources to heat themselves; they move as the sun shifts in order to get an optimal internal temperature.[7]
These iguanas are characterized by the growth of bony prominent tubercles on their snouts which resemble horns.[8] Males possess an adipose pad in the form of a helmet on the occipital region of the head, and a large dewlap. This species, like other species of Cyclura, is sexually dimorphic; males are larger than females, and have more prominent dorsal crests and "horns" in addition to large femoral pores on their thighs, which are used to release pheromones.[9][10]
Ranging in scattered locations throughout Hispaniola (in both Haiti and the Dominican Republic), populations are stable only on Isla Beata and the extreme of the Barahona Peninsula, inside Jaragua National Park.[1][5] There are moderately dense populations in the southeastern region of Haiti and its offshore islands, including the brackish lake of Étang Saumâtre, as well as the Dominican hypersaline Lake Enriquillo and its lake island, Isla Cabritos. Populations in Haiti are even more endangered due to deforestation, poaching for bushmeat, and human clearing practices.
Though not restricted to one single habitat, the iguanas are found most abundantly in scrub woodlands of the Hispaniolan dry forests (characterized by xeric, rocky terrain of eroded limestone with minimal flora), coastal terraces, lowlands of the mainland, plus several offshore islands and small cays, all with slightly different habitat types.[1][5] The favored biome of the rhinoceros iguana to live within is one that receives very little rain and has few trees or shrubs. True to the name “rock” iguana, they favor rather barren landscapes with smooth, large boulder formations and rocky outcrops for basking on, with adequate crevices and sheltered areas for retreating into. They will immediately flee into the rocks and crevasses to hide from predators such as humans, birds of prey, feral dogs and cats.
This species has been known to exhibit phenotypic plasticity like other iguanas. While historically present near coastlines, human activity and introduced predators have forced rhinoceros iguanas inland.[11]
An individual was photographed on May 4, 2008 on Limbe Island in northern Haiti. It had been caught by a group of fishermen from Bas-Limbe, Bord de Mer village. The rhinoceros iguanas caught on Limbe Island are illegally eaten by the local population. This sighting represents a new area previously not thought to be in the range of C. cornata.
Aside from Hispaniola and its surrounding islands, the rhinoceros iguana was previously found on Navassa Island (with an endemic subspecies: C. c. onchiopsis), but was extirpated there.
Rhinoceros iguanas, like most members of Cyclura, are usually docile and well-tempered. As with many lizard species, “head-bobbing” is a commonly observed form of communication used by the rhinoceros iguana. Males, especially, appear to “nod” their heads toward one another as an assertion of dominance, or announcing their “ownership” of an area. It is oftentimes a warning to not come any closer, as well as to communicate (with females) their desire to mate. At times, this form of body language is directed at humans (by both wild and captive iguanas) as a warning, or as a sort of “greeting” to their human caretaker(s). The females (more or less) only nod their heads to ward off incessant advances from males, and female-to-female head bobbing is infrequent, though not nonexistent.
In general, rhinoceros iguanas (especially captive bred individuals) are among the most docile and human-tolerant of reptiles; some iguanas appear to desire human attention, seeming to enjoy being petted as much as a domestic dog or cat would. Even with this overall docility, levels of human tolerance can vary greatly from iguana to iguana, season to season, and even day by day. Iguanas are highly in-tune with their surroundings, being particularly sensitive to atmospheric and energetic nuances. A normally friendly iguana may have “mood swings”, or show a desire to be left alone, for unknown reasons. Though they prefer to flee when attacked or threatened, they will aggressively attack by biting and repeatedly striking with their thick tail if cornered. Their long claws can also cause significant scratches (even drawing blood), though this is not necessarily a defensive act, but can simply result from handling a more friendly iguana. Some owners opt to wear thick, long leather gloves, even with docile individuals.[5][12]
The rhinoceros iguana, like most Cyclura species, is primarily herbivorous, consuming leaves, flowers, berries, and fruits from different plant species.[9] A study in 2000 by Dr Allison Alberts of the San Diego Zoo revealed that seeds passing through the digestive tracts of Cyclura species 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 rhinoceros iguana is also an important means of distributing these seeds to new areas (particularly when females migrate to nesting sites) and, as the largest native herbivores of their island's ecosystem, they are essential for maintaining the balance between climate and vegetation.[14] Rhinoceros iguanas do appear to be opportunistic carnivores, as individual animals have been observed eating small lizards, snakes, and insects.[5]
The rhinoceros iguana's only confirmed native predator is the Hispaniola racer (Haitiophis anomalus), a large snake which has been recorded to give chase to juvenile iguanas, as well as wait for them outside the exit holes of their burrow.[15] However, most predation of iguanas comes from invasive species like feral dogs (Canis familiaris), feral cats (Felis catus), small Indian mongooses (Urva auropunctata), and feral pigs (Sus domesticus), which all feed on eggs, adults, and juveniles.
Male rhinoceros iguanas, unlike other members of the genus Cyclura, reach sexual maturity at four to five years of age.[9] Females become sexually mature at two to three years of age.[5] Male rhinoceros iguanas are territorial and the most aggressive males will have the largest range of territory.[1] 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.[1][9] Females lay from 2 to 34 eggs, with an average clutch size of 17, within 40 days.[9] Females guard their nests for several days after laying their eggs, and incubation lasts approximately 85 days.[1]
Notably, despite rhinoceros iguanas exhibiting some sexual dimorphism in size and horn development, they exhibit comparatively less sexual dimorphism than most other iguanas. Both male and female rhinoceros iguanas lack prominent mid-dorsal spines on their neck, which are typically very large in male iguanas of other species, both have well-developed dewlaps, and both develop horns.[16] By contrast, in many other animals that exhibit horns such as ungulates or rhinoceros beetles, horns are often only present in males. Rhinoceros iguanas are also reported to show less dimorphism in size than other iguana species.[16] This reduced dimorphism has been suggested to be due to intense female-female competition in rhinoceros iguanas, given the scarcity of nesting sites in their island environment, and females will use their horns to fight with one another over access to nesting sites much as males fight for access to females.[16] Similar female-female combat over nesting sites has been documented in other island iguanas such as the marine iguana.[17]
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Although rhinoceros iguanas are the most common species of Cyclura kept in captivity, approximately 10,000-16,000 iguanas remain in the wild.[18] A successful breeding program existed at the Parque Zoológico Nacional of the Dominican Republic (ZooDom) from 1974 to 1994, with an average of 100 babies hatching annually.[1] These efforts included reintroductions of captive-bred "head-started" young to several protected areas in the southwest Dominican Republic, in order to reduce the odds of predation by snakes and introduced carnivorans, such as mongooses or feral cats and dogs.[1] The program has not continued since 1995, due to an administrative change at the zoo.[1] International trade in the species is regulated under the Appendix I of the Convention on International Trade in Endangered Species.[3] Illegal logging, competition from domestic grazers (cows, pigs, goats), predation on young by invasive species, limestone mining, harvesting for the pet trade, hunting for bushmeat, pollution, and wildfires are all manmade threats to the rhinoceros iguana's survival.[19]
The rhinoceros iguana is well established in captivity, both in public and private collections.[9] As of 2007, rhinoceros iguanas were present in captivity throughout the United States (total 39 males, 32 females, and 36 undetermined individuals) at 20 zoological institutions, with an additional 533 animals of unassigned subspecies, reported by seven American Zoological and Aquarium Association institutions.[1] The actual number may be much higher, considering animals kept at European and Asian zoos, and the amount kept as pets in private collections.[1] As a result, the demand for wild-caught animals to supply zoos and the pet trade has been reduced.[1][9]
C. cyclura lair, Jaragua National Park
C. cyclura, Jaragua National Park
Video of a rhinoceros iguana at Colchester Zoo
{{cite web}}: CS1 maint: url-status (link) The rhinoceros iguana (Cyclura cornuta) is an endangered species of iguana that is endemic to the Caribbean island of Hispaniola (shared by Haiti and the Dominican Republic) and its surrounding islands. A large lizard, they vary in length from 60 to 136 centimetres (24 to 54 in), and skin colours range from a steely grey to a dark green and even brown. Their name derives from the bony-plated pseudo-horn or outgrowth which resembles the horn of a rhinoceros on the iguana's snout. It is known to coexist with the Ricord's iguana (C. ricordii); the two species are the only taxa of rock iguana to do so.
