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Black Spinytail Iguana (Ctenosaura similis)


First year: 1978

Established status: Populations are confirmed breeding and apparently self-sustaining for 10 or more consecutive years.

Estimated Florida range: 3 counties  At least 10 years, 2 counties  Less than 10 years

Statewide trend: Expanding

Threats to natives: Expanding

Species Account: 

This species is native to both drainages of southern Mexico and has established populations in Dade, Lee, and Charlotte counties in Florida. It is difficult to distinguish this species from the Mexican spinytail iguana (Ctenosaura pectinata), but Ctenosaura similis has 0-2 scales separating the short crest along the back and tail, 2 complete rows of intercalary scales between the whorls of enlarged scales on the tail, and dark dorsal crossbands (Köhler and Streit 1996). Adult males may reach nearly 1.2 m (4 ft) in length. These primarily terrestrial lizards are extremely wary and typically dash to their burrows, although they will climb agilely if they cannot reach their burrows (Bartlett and Bartlett 1999). According to Wilson and Porras (1983), Eggert (1978) misidentified a population of this species along Old Cutler Road in Miami, but black spinytail iguanas are found on Key Biscayne in Dade County (Townsend et al. 2003).


Coastal upland, Exotic plant community, Low density suburban development, areas peripheral to core urban areas, and small towns, Agricultural habitat


Bartlett, R. D., and P. P. Bartlett. 1999. A field guide to Florida reptiles and amphibians. Gulf Publishing Company, Houston, Texas. 278pp.

Eggert, J. 1978. The invasion of the wish willy. Florida Wildlife 31(5):9-10.

Köhler, G., and B. Streit. 1996. Notes on the systematic status of taxa acanthura, pectinata, and similis of the genus Ctenosaura (Reptilia: Sauria: Iguanidae). Senckenbergiana Biologica 75:33-43.

Krysko, K. L., F. W. King, K. M. Enge, and A. T. Reppas. 2003. Distribution of the introduced black spiny-tailed iguana (Ctenosaura similis) on the southwestern coast of Florida. Florida Scientist 66:141-146.

McKercher, E. 2001. Ctenosaura pectinata (Iguanidae) on Gasparilla Island, Florida: colonization, habitat use and interactions with Gopherus polyphemus. M.S. Thesis, University of Florida, Gainesville, Florida, USA. 117pp.

Townsend, J. H., K. L. Krysko, and K. M. Enge. 2003. The identity of spiny-tailed iguanas, Ctenosaura, introduced to Florida, USA (Squamata: Sauria: Iguanidae). Herpetozoa 16:67-72.

Wilson, L. D., and L. Porras. 1983. The ecological impact of man on the south Florida herpetofauna. University of Kansas Museum of Natural History, Special Publication No. 9. 89pp.