Description: One of 2 subspecies of rhinoceros iguanas. This species is easily identified by its scales around the face that protrude and one large horn-like scale on the snout. Other characteristics setting this species apart are large jowl muscles and two fatty pads on the crown of the head. For the Mona Island subspecies, males of this species average over 2.5 feet in length with females averaging 1.5 feet in length. Adults are a gray, olive, or brown color and hatchlings are light grey or tan with dark banding.

Distribution: Endemic to Mona Island, a small remote island between Puerto Rico and Hispanola.

Habitat: This subspecies primarily occupies rocky slopes on cliffsides. Females must migrate inland to nest in sandy areas but may also nest in sinkhole depressions if preferred nesting sites are not available.

Reproduction: Nesting females fight over preferred nesting sites and defend nests after they are laid. The average clutch size is 12 eggs.

Closely related to the Rhinoceros iguana from nearby Hispaniola, and bearing the same characteristic facial adornments, the Mona Island iguana is restricted to one tiny island lying midway between Puerto Rico and Hispaniola. Part of the commonwealth of Puerto Rico, Mona Island is a protected natural reserve that receives funding from the U.S. Fish & Wildlife Service. Population numbers have been reliably estimated at 1,500, which are considered abnormally small, with far lower densities than similar iguana-inhabited islands. Also disturbing is the fact that immature iguanas are scarce and represent only 5 - 10% of the population, indicating that the population is aging and declining. This is owing to the presence of introduced exotic species. Feral pigs root up iguana nests, and cat predation is a serious threat to young iguanas, hence juvenile recruitment is very low. Current conservation measures include the construction of pig exclosure fences around known coastal nesting sites and an active headstarting program. Additionally, heavy recreation activity in sandy coastal areas during nesting season and browsing of native plants by feral goats are compounding the conservation issues on Mona Island.

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For more detailed species information, please refer to the IUCN-ISG Taxonomic Account for the Mona Island Iguana, Cyclura cornuta stejnegeri.

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