Reptiles
Black Spiny-tailed Iguana
Ctenosaura similis · also called black spiny-tailed iguana, black iguana
Nothing else on four legs and scales has been measured moving faster than a black spiny-tailed iguana, clocked at over 34 kilometres per hour in a full sprint, a genuine world record for lizards. If speed fails, it has a backup plan: a long tail covered in sharp spines that can deliver a whip-like strike forceful enough to actually hurt whatever is chasing it.
Overview
The black spiny-tailed iguana, Ctenosaura similis, is a large, adaptable lizard native to Central America, tolerating forest, grassland, and disturbed coastal habitat alike. An opportunistic omnivore, it eats plants, insects, small lizards, and even eggs, sheltering in rock crevices and burrows.
Record speed, and a spiny backup
Its explosive sprinting speed is the fastest ever recorded in any lizard, and its heavily spined tail delivers a genuinely forceful defensive strike if cornered. That same adaptability has let it establish thriving invasive populations in parts of Florida after pet-trade releases.
Status
Least Concern — common and widespread across its native Central American range, and successful enough as an introduced species elsewhere to raise separate ecological concerns.
Black Spiny-tailed Iguana: common questions
How fast can a black spiny-tailed iguana actually run?
The species holds the officially recognised record for the fastest running speed ever measured in any lizard, having been clocked sprinting at over 34 kilometres per hour, a speed considerably faster than any other lizard species tested, reflecting powerful hind legs and a body built for rapid, explosive bursts of movement to escape danger and reach shelter quickly.
Can the tail spines on this iguana actually hurt a predator?
Yes, the tail is covered in whorls of enlarged, sharp spines, and when the iguana whips its tail at a threat, the combination of the tail's length, muscular strength, and sharp spines can deliver a forceful strike capable of causing real pain or injury, making the tail a genuinely effective defensive weapon rather than just a passive physical feature.
Why has the black spiny-tailed iguana become invasive in Florida?
Individuals released or escaped from the exotic pet trade found conditions in parts of Florida suitable for survival and reproduction, and the species' broad dietary flexibility, tolerance for disturbed habitat, and generally opportunistic behaviour have allowed it to establish self-sustaining wild populations there, where it can compete with native wildlife for food, shelter, and nesting sites.
Is the black spiny-tailed iguana dangerous to humans?
The species is not considered a significant danger to humans under normal circumstances, though a cornered or handled individual can deliver a painful bite and a forceful tail strike using its spined tail if it feels seriously threatened, so like most large lizards, careful and respectful handling is recommended to avoid provoking a defensive response.