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Mona Island Iguana

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Scientific Name: Cyclura stejnegeri

IUCN Red List Status: Endangered

Description: Previously considered a subspecies among 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.  Males average over 2.5 feet in length with females averaging 1.5 feet in length.  Adults are gray, olive, or brown overall and hatchlings are light grey or tan with dark banding.

Distribution: Mona Island

Habitat:  Primarily occupies rocky slopes on cliffsides on Mona Island.  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. 

Notes: 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 U.S.  commonwealth of Puerto Rico, Mona Island is a protected natural reserve that receives funding from the U.S. Fish & Wildlife Service.  Population size has been reliably estimated at 1,500, which is 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.  The primary threat today is 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 concerns on Mona Island. 

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