Cyclura cornuta
horned ground iguana
(Also: rhinoceros iguana)

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.

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)

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).

These iguanas hatch from eggs and are independent after hatching. They mature at 5 to 9 years of age (Cyclura.com 2002).

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).

Like all Iguanas, C. cornuta are behavioral heliotherms. This means that they must adjust their activity patterns to utilize solar radiation so as to regulate their body temperature. It also means that there are some obvious habitat restrictions for this animal--it can only survive in tropical or sub-tropical climates in the wild. When kept as a pet, it is often necessary to provide this species with an auxillary source of heat (such as a lamp) as many homes are kept below the appropriate temperature (Houston Zoo).

Most of the documented behavior unique to C. cornuta revolves around mating behavior. The aggressive displays that accompany mate guarding and territoriality have been discussed above (Hunsaker, et al. 1969)

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).

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.

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.

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.

Rhinoceros iguanas are sometimes kept as pets, and in the past have been used as food. Currently they are not of great economic importance.

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.

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.