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Publication #WEC307

Quick Reference Guide: Large Lizards in Florida1

Steve A. Johnson and Monica E. McGarrity2

The non-native lizards breeding in Florida now outnumber the native species, and there are several large, invasive lizards that are of special concern. This fact sheet, best viewed as a pdf (, is a quick reference guide to identification of the largest lizards you are likely to see in Florida, and the appropriate action to take in the event of an encounter. Report sightings and view maps of locations where each species has been encountered in Florida by visiting the EDDMapS Florida invasive species reporting portal online at Learn more about how to scan for, recognize, and report introduced reptiles by completing the Introduced Reptile Early Detection and Documentation training course. Visit to learn more and get REDDy!


American Alligator (Alligator mississippiensis)

STATUS: native species found throughout Florida

SIZE: grows to 14 ft. long

BODY: black; juveniles (up to 6 ft. long) with light-colored bands that fade with age

OTHER: enlarged, bony scales and webbed feet with claws

NOTE: Alligators are reptiles (i.e., Class Reptilia) but they are not lizards (Order Squamata) – they are crocodilians (Order Crocodilia).

Figure 1. 

Juvenile American Alligators. Credits: Ianare Sevi, Wikimedia Project

[Click thumbnail to enlarge.]


To learn more about how to recognize and report invasive carnivorous lizards, get REDDy – visit http://ufwildlife.ifas.ufl.edy/reddy.shtml

Nile Monitor (Varanus niloticus)

STATUS: breeding populations in southern Florida in Lee County and potentially also in Miami-Dade, Broward, and Palm Beach Counties; other monitor lizard species are occasionally sighted, likely escaped or released pets

SIZE: grows to ~6 ft. long

HEAD: V-shaped marks on neck behind eyes

BODY: grayish brown; rows of lighter spots across body, spots fuse into bands on tail

Figure 2. 

Nile Monitor Lizard. Credits: Patrick Lynch, South Florida Water Management District, 2007

[Click thumbnail to enlarge.]

Giant Argentine Tegu a.k.a. Black-and-White Tegu (Tupinambis merianae)

STATUS: breeding populations in southern Miami-Dade and Hillsborough Counties; other tegu species are occasionally sighted, likely escaped or released pets

SIZE: can grow to over 4 ft. long

HEAD: greenish when young

BODY: grayish to reddish; marked with dark bands

Figure 3. 

Giant Argentine Tegu. Credits: Mario Sacramento, Universidade de Alfenas, Brazil (adult image); David Barkasy, (juvenile image)

[Click thumbnail to enlarge.]


Upload photos to document sightings by visiting

Black Spiny-tailed Iguana (Ctenosaura similis)

STATUS: breeding populations in Sarasota, Lee, Charlotte, Collier, Broward, and Miami-Dade Counties

SIZE: can grow to over 4 ft. long

BODY: grayish; marked with dark bands; spikes down the back (more prominent in males) and rings of spikes around the tail

Figure 4. 

Black Spiny-tailed Iguana. Credits: Steve A. Johnson, University of Florida, 2009

[Click thumbnail to enlarge.]

Green Iguana (Iguana iguana)

STATUS: breeding populations in Lee, Collier, Monroe, Miami-Dade, Broward, and Palm Beach Counties; sightings and potential for breeding as far north as Indian River County on the East Coast

SIZE: grows up to 6 ft. long

HEAD: may be reddish; large, round scale on each cheek; large throat fan (dewlap)

BODY: greenish to grayish (juvenile bright green); tail with dark bands; spikes down the back

Figure 5. 

Green Iguana: adult (upper), juvenile (lower right), showing cheek scale and reddish breeding color (lower left). Credits: Steve A. Johnson, University of Florida (upper); Arria Belli, Wikimedia Project (lower right); Tony Pernas, National Park Service (lower right)

[Click thumbnail to enlarge.]


This project was made possible in part by a grant from the South Florida National Parks Trust and the Ferris Greeney Family Foundation, and by the USDA-RREA. This document was originally created as additional reference material for the Introduced Reptile Early Detection and Documentation training program, also known as REDDy. For more information, visit



This document is WEC307, of the Department of Wildlife Ecology and Conservation, UF/IFAS Extension. Original publication date March 2011. Reviewed February 2014. Visit the EDIS website at


Steve A. Johnson, associate professor and Extension specialist, Department of Wildlife Ecology and Conservation, 110 Newins-Zeigler Hall, P.O. Box 110430, Gainesville, FL 32611; and Monica E. McGarrity, biological scientist, Gulf Coast Research and Education Center, University of Florida/IFAS - Plant City Center, 1200 North Park Road, Plant City, FL 33563.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.