Overview
The Serpent Island Gecko (Nactus serpensinsula) is a critically localized, slender-toed gecko endemic to tiny uninhabited volcanic islets lying north of Mauritius in the Indian Ocean. Driven entirely from the Mauritian mainland following human colonization and the introduction of invasive mammalian predators, this resilient reptile survived solely upon precipitous oceanic cliffs. It represents an exceptional ecological relict adapted to arid, seabird-dominated volcanic environments.
Biology and Physical Characteristics
Nactus serpensinsula displays a slender, compressed body with a flattened triangular head and large golden eyes equipped with vertical slit pupils. Lacking the expanded adhesive toe-pads of arboreal geckos, its long, slender digits terminate in curved, needle-sharp claws engineered specifically for clambering over jagged basalt rock and loose volcanic scree. Its dorsal coloration consists of cryptic mottled greyish-browns and pale buff transverse bands that blend seamlessly into weathered sea cliffs.
Behavior and Ecology
Strictly nocturnal and terrestrial, the Serpent Island gecko shelters deep within cool rock fissures and under slabs of volcanic tuff during the scorching tropical day. As dusk settles, it emerges to hunt abundant invertebrate prey that thrives on nutrient-rich guano deposited by nesting colonies of sooty terns, red-tailed tropicbirds, and shearwaters. Females deposit hard-shelled clutches of two eggs in communal rock crevices, where ambient maritime humidity aids incubation.
Conservation and Human Impact
Assessed as Vulnerable by the IUCN, the species historically occupied only the single, rat-free fortress of Serpent Island. In recent decades, the Mauritian Wildlife Foundation and national conservation bodies successfully eradicated invasive rabbits and goats from neighboring Round Island, allowing native hardwoods to regenerate. Subpopulations of Nactus serpensinsula were carefully translocated there, successfully establishing a vital second reproducing wild colony.
Interesting Factoid
Despite its name, there are zero snakes on Serpent Island; the gecko’s sole home is a sheer volcanic rock fortress in the Indian Ocean where the geckos survive by hunting flies that feed on seabird guano.
Last updated: October 2026