Overview
The Anegada Ground Iguana (Cyclura pinguis), also known as the Stout Rock Iguana or Anegada Rock Iguana, is an imposing, prehistoric lizard native to the coral island of Anegada in the British Virgin Islands. As the most basal and ancestral member of the genus Cyclura, it is an evolutionary relic from the ancient origins of West Indian rock iguanas. Once abundant across the Puerto Rico bank, it is now confined to fragile limestone scrub, where an intensive head-start program is rescuing it from the brink of extinction.
Biology and Physical Characteristics
Cyclura pinguis is an exceptionally robust, heavy-bodied lizard possessing a thick, muscular neck and powerful limbs. Adult coloration is highly variable and visually striking: mature individuals are typically a rich brownish-grey to olive-khaki, washed with vivid sky-blue to turquoise highlights across the dorsal crest, legs, and tail, while large adult males develop prominent swollen jowls and a fleshy adipose crest atop the head. A continuous row of stiff, erect, comb-like spines extends from the nape down the center of the back. Its muscular, laterally compressed tail can deliver punishing defensive lashes against threats.
Behavior and Ecology
Anegada Ground Iguanas are terrestrial, diurnal baskers that establish large territories across the weathered limestone bedrock (locally called ‘the bench’). They shelter from extreme heat and predators inside deep natural limestone caves, sinkholes, and hollow solution pockets formed by millions of years of coral reef erosion. They are gentle herbivores that spend hours foraging across the scrub for seasonal fruits and flowers, acting as vital seed dispersers for Anegada’s endemic flora. In early summer, females dig elaborate subterranean nesting tunnels in sandy clearings, aggressively guarding their nest mounds for weeks against rivals.
Conservation and Human Impact
The Anegada Ground Iguana is classified as Critically Endangered on the IUCN Red List. While adult iguanas have virtually no natural predators on Anegada, the introduction of non-native mammals caused catastrophic declines: feral cats, dogs, and rats devoured over 90% of wild hatchlings, causing wild recruitment to crash. In response, the National Parks Trust of the Virgin Islands and international zoos launched a renowned ‘headstart’ facility in 1997, raising hatchlings in predator-proof enclosures until they reach a cat-safe size of two pounds before releasing them back into wild scrub.
Interesting Factoid
The Anegada Ground Iguana is the great-grandparent of all Caribbean rock iguanas—a living fossil whose ancestors roamed the Caribbean millions of years ago, living in subterranean limestone caves hollowed out by ancient coral reefs.