Enge, Kevin M.

Krysko, Kenneth L.

Townsend, Josiah H.

English

The University of Kansas: Journals@KU

Researchers have been aware of the pres-ence of non-native reptiles and amphib-ians in Florida for more than 140 years.Cope (1863) reported the small, terres-trial Greenhouse Frog, Eleutherodactylusplanirostris (Cope), from southern Florida, andthe report of Anolis sagrei followed about 25 yearslater (Garman 1887). Since then, numerous papershave detailed the introduced herpetofauna ofsouthern Florida (e.g., Carr 1940, Duellman andSchwartz 1958, King and Krakauer 1966, Wilsonand Porras 1983, Butterfield et al. 1997), andmore than 40 non-native species are presentlyreported. These reptiles and amphibians were ini-tially introduced and their populations are supple-mented via various routes. Some of these exoticsmay find their way into the suitable climate ofsouthern Florida as stowaways in shipments ofornamental plants and other commerce, but manyrecent introductions can be attributed to individ-Introduced Iguanas in Southern Florida: A History of More Than 35 YearsJosiah H. Townsend1, Kenneth L. Krysko1, and Kevin M. Enge21Division of Herpetology, Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611-78002Florida Fish and Wildlife Conservation Commission, Joe Budd Wildlife Field Office, 5300 High Bridge Road,Quincy, Florida 32351All photographs are by the senior author except where noted.111IGUANADecember 2003Adult female Ctenosaura similis on Key Biscayne using an old park bench as a basking site. Photograph by Joe Burgess.uals being intentionally released by or escapingfrom reptile dealers or pet owners. As the trade inreptiles and amphibians has increased, so has thenumber of exotic species that have become estab-lished. Some of the more notable, and noticeable,of these species are three large lizards in the familyIguanidae (sensu Frost et al. 2001): the MexicanSpiny-tailed Iguana, Ctenosaura pectinata(Wiegmann), the Black Spiny-tailed Iguana, C.similis (Gray), and the Green or Common Iguana,Iguana iguana (Linnaeus). Lizards in the genus Ctenosaura are com-monly referred to as Spiny-tailed Iguanas orCtenosaurs. They are large iguanids that typicallyhave tails ringed with rows of enlarged, spinyscales. Presently, 17 species are recognized.Ctenosaurs are found in southern Baja California,its offshore islands, and on mainland CentralAmerica from adjacent parts of Mexico to Panama(Köhler 2002; see also IGUANA 10(2):56–57and 10(3):79–81). Two of these species, C. pecti-nata and C. similis, are known to be established insouthern Florida.Ctenosaura pectinata is native to the Pacificversant of southern Mexico. This species was firstreported in Florida by Eggert (1978), whodescribed digging up eggs and observing adultsnear Old Cutler Road in southeastern Miami-Dade County. However, Eggert (1978) erro-neously identified this population as C. similis,which was later corrected by Wilson and Porras(1983). This case of mistaken identity was the firstin a series of misidentifications involving intro-duced Ctenosaurs in Florida, as C. pectinata wassubsequently reported from Key Biscayne(Butterfield et al. 1997), Gasparilla Island (Bartlettand Bartlett 1999, McKercher 2001, McCoid2002), and from “… the streets and trees of met-ropolitan Miami” (Bartlett and Bartlett 1999).After examining all Florida specimens ofCtenosaura in systematic collections and collectingspecimens from all known localities in southernFlorida, Townsend et al. (2003) concluded thatmost populations (including those known fromKey Biscayne and Gasparilla Island) are C. similis,and the only extant population of C. pectinataoccurs near the original Old Cutler Road site. Wevisited the Old Cutler Road site at least six timesfrom 2002–2003 and observed two adult males,six adult females, and one subadult of unknownsex living on and adjacent to a single private prop-erty east of Old Cutler Road between SW 168thand SW 184th streets. No other C. pectinata wasseen, and local residents with whom we talkedwere unfamiliar with the lizards and unaware oftheir presence. However, one resident of theFlorida Keys related that she had observedCtenosaurs crossing Old Cutler Road while dri-ving through the area in 2002 and 2003 (H.Kavney, pers. comm.).Ctenosaura similis is native to CentralAmerica, and is found from the Isthmus ofTehuantepec to northeastern Nicaragua and west-112 IGUANA Volume 10, Number 4Three species of iguanas have become established insouthern Florida: Ctenosaura pectinata, from near OldCutler Road (top), southeastern Miami-Dade County, andadult male Ctenosaura similis (middle), and Iguana iguanafrom Key Biscayne (bottom).ern Panama on the respective Atlantic and Pacificversants. The extent to which C. similis hasbecome established in southern Florida is onlynow becoming clear. One of the earliest knownpopulations of C. similis in Florida occurs on KeyBiscayne. That population probably has persistedthere since at least 1979, when the Crandon ParkZoo was closed and most of the exhibit animalswere relocated to the Miami Metrozoo(Townsend et al. 2003). Since its introduction onKey Biscayne, C. similis has become well-estab-lished in Crandon Park and is being found inincreasing numbers in Bill Baggs Cape FloridaState Park at the southern end of Key Biscayne (E.Donlan and E. Golden, pers. comm.). Thisspecies also was introduced on Gasparilla Island,Charlotte and Lee counties, on Florida’s south-western Gulf Coast during the late 1970s or early1980s, when an island resident released as few asthree individuals brought back from Mexico(Krysko et al. 2003). Ctenosaura similis nowoccurs on Gasparilla Island in large numbers andhas expanded its range onto the adjacent main-land and onto Cayo Costa, a small island south ofGasparilla Island. Large populations also occur onKeewaydin and Little Marco islands and withinthe boundaries of the Rookery Bay EstuarineResearch Reserve, Collier County. The latter pop-ulation was established in 1995, when aKeewaydin resident intentionally (and illegally)released 5–30 C. similis on his property (Kryskoet al. 2003). The deliberate introduction of non-native reptiles is illegal according to FloridaStatute 372.265, which specifically prohibits therelease of exotic wildlife without a permit fromthe Florida Fish and Wildlife ConservationCommission.Confusion regarding the identities of southernFlorida’s Ctenosaurs may be attributed partially toa general similarity in the appearance of the twospecies. As adults, both C. pectinata and C. similisare large, dark-colored terrestrial lizards that may113IGUANADecember 2003Map of South Florida showing localities mentioned in the article.appear striped or banded. Juveniles of both speciesare green at the time of hatching, gradually takingon the brown or black adult coloration as theymature. However, these two species may be dis-tinguished easily by using a few morphologicalcharacters that were defined by Köhler and Streit(1996) and later applied by Townsend et al.(2003) to Florida Ctenosaurs. Adult C. similis usu-ally have a gray or tan ground color with 4–12well-defined dark dorsal bands that extend nearlyto the ventral scales. Male C. similis also may takeon an orange color around the head and throatduring the breeding season. In contrast, mature C.pectinata have a black to brown ground colormarked with irregular whitish blotches, with addi-tional white coloration usually apparent in the areaof the neck and throat. These white markings maygive C. pectinata a partially banded appearance.Both C. similis and C. pectinata have tails that areringed with rows of enlarged spiny scales, orwhorls, that are separated by smaller smooth scales,or intercalaries — but differ in the number ofintercalaries that separate the whorls. This is mostapparent near the base of the tail. Ctenosaura sim-ilis has whorls separated by two rows of intercalar-ies and C. pectinata has whorls separated by threerows of intercalaries. Florida C. similis also tend tohave very few (usually zero) small dorsal scalesbetween the posterior end of the dorsal crest andthe anterior end of the caudal crest, whereasFlorida C. pectinata usually has 7 or 8 (range0–20) dorsal scales between crests (Townsend etal. 2003).Currently, C. pectinata appears to be restrictedto a single small area around Old Cutler Road, andoccurs in low numbers there despite having beenintroduced at least 25 years ago. Expansion of thispopulation may have been limited by natural andman-made geographic barriers, including a canalto the north, construction in the early 1980s of alarge corporate headquarters to the south,114 IGUANA Volume 10, Number 4Adult female (right) and an adult male andfemale (below) Ctenosaura pectinata near OldCutler Road, southeastern Miami-Dade County.(below) Adult maleCtenosaura similis,Key Biscayne.Biscayne Bay to the east, and Old Cutler Road tothe west. A large area directly to the south of thecurrent population was developed since the time itwas reported by Wilson and Porras (1983), aprocess which may have reduced the numbers ofC. pectinata to the low numbers seen today. Incontrast, C. similis has been an exceedingly suc-cessful invader, becoming well-established andexpanding its range in a number of Florida locali-ties. Site fidelity associated with Ctenosaura uti-lization of holes or other refugia may slow theprocess of range expansion beyond the original siteof introduction. Nonetheless, neither species ofCtenosaura has been nearly as successful as aninvader as their familiar relative, the Green orCommon Iguana (Iguana iguana).Iguana iguana is one of the most popular rep-tiles in the pet trade, with over 1.14 millionimported into the United States in 1995 alone,and represents about 45% of all reptilian imports(Hoover 1998). Iguana iguana has a wide nativerange and is found at low elevations on the main-land from Sinaloa, Mexico south to Ecuador onthe Pacific versant and Veracruz, Mexico to south-ern Brazil on the Atlantic versant, as well as onsome Central and South American coastal islands115IGUANADecember 2003Juvenile Ctenosaura similis, Key Biscayne.Adult male Iguana iguana, Key Biscayne.Three Green Iguanas (Iguana iguana) sit at canal’s edge,Key Biscayne.and throughout the Lesser Antilles. In the UnitedStates, I. iguana has been introduced in southernFlorida and Hawaii (McKeown 1996). Iguanaiguana was first reported in southern Florida byKing and Krakauer (1966), who indicated thatiguanas could be found on Key Biscayne, Hialeah,Coral Gables, and near the Miami InternationalAirport. Iguana iguana has since become estab-lished at least as far north as Palm Beach Countyon the Atlantic Coast and Lee County on the GulfCoast (Bartlett 1980, Bartlett and Bartlett 1999,Townsend et al. 2002, Krysko et al. in press), andas far south as Stock Island in the Florida Keys,Monroe County. In all likelihood, this species ismuch more abundant in southern Florida thanpreviously reported in the literature. The largestpopulations of I. iguana probably occur in easternMiami-Dade County on Key Biscayne, in FairchildTropical Garden, and Matheson Hammock Park,but these lizards are now found at localitiesthroughout the county and have been sightednumerous times in Everglades National Park(Meshaka et al. 2000).In Florida, I. iguana usually is found nearwater, often in trees or on embankments border-ing canals and lakes, or even basking on lawns orpavement in urban and suburban areas. Juvenilesand adults are strictlyherbivorous. InFlorida, iguanas eat awide variety of bothexotic ornamentals andnative plants (seeIGUANA10(3):94–95). Iguanaiguana on KeyBiscayne nests in sandyareas, often with multi-ple females utilizing asingle small area. Most hatchlings appear duringJuly and August. Relatively few predators of juve-niles occur in the urban and suburban areas ofsouthern Florida, a factor that may lead to rapidgrowth in any introduced I. iguana populationthat contains multiple reproducing females. Lackof predators and abundance of food are some ofthe primary explanations for the very high popula-tion densities of I. iguana found in southernFlorida.Bill Baggs Cape Florida State Park (CFSP)occupies 174 ha at the southern end of KeyBiscayne, almost all of it consisting of coastalstrand habitat dominated by Saw Palmetto(Serenoa repens) or coastal hammock dominated byButtonwood (Conocarpus erectus) and Sea Grape(Coccoloba uvifera). In 2003 alone, CFSP staffremoved over 500 Green Iguanas (E. Donlan,pers. comm.). However, thousands of iguanas liveon Key Biscayne outside of CFSP, and, when an I. iguana is removed from the grounds of CFSP,other iguanas from outside the park simply movein and take up available space. Low winter tem-peratures appear to be a major factor limiting thenorthern expansion of I. iguana in Florida; how-ever, a freeze in Miami-Dade County during thewinter of 2002–2003 did little more than tem-116 IGUANA Volume 10, Number 4An obviously gravid female Iguana iguana pauses whileexcavating her nest at Key Biscayne. Photographs by EstherM. Langan.porarily reduce numbers (see IGUANA10(3):98). Interestingly, many I. iguana havelearned to seek shelter in burrows or under build-ings, and we have observed I. iguana takingrefuge under water, exposing only their snouts forbreathing, to escape extremely cold temperatures. Another large iguanid, the HispaniolanRhinoceros Iguana or Cyclura cornuta(Bonnaterre), was reported in very small numbersin the vicinity of the Miami Seaquarium onVirginia Key and also possibly on Key Biscayne(King and Krakauer 1966). A few individuals ofthis species escaped from an exhibit at theSeaquarium and are purported to have repro-duced in small numbers (Bartlett and Bartlett1995). However, we have not observed thisspecies in the wild, and no specimens from Floridaare known to have been deposited in any system-atic collections.With the ranges and population sizes ofCtenosaura similis and Iguana iguana continuingto grow and the population of C. pectinata per-sisting for over 25 years, these species obviouslyhave become a permanent part of the dynamicherpetofauna of southern Florida. These threelizard species are only a few of the growing num-ber of introduced reptiles and amphibians that callsouthern Florida home. This number seems to beincreasing as quickly as researchers are able toinvestigate each new report of a possible intro-duced species. Without importers and pet ownersshowing greater responsibility and stricter enforce-ment of Florida state laws regarding the release ofexotic animals, what remains of the native her-petofauna in southern Florida stands a goodchance of being displaced by exotic species in thenear future.AcknowledgementsWe thank Kevin Kirwin and Ernest Link ofCrandon Park; Elizabeth Golden and Ellen Donlanof Bill Baggs Cape Florida State Park; ReggieNorman, Ken Alvarez, Chris Angel, and PattyMiddleton of Gasparilla Island State Park; andSteve Bertone of Rookery Bay Estuarine ResearchReserve for facilitating field work at their respectiveparks and for providing much useful information.Helen Kavney provided additional information.117IGUANADecember 2003A Buttonwood Tree(Cornocarpus erectus)provides food and a place tobask for this Green Iguana(Iguana iguana) on WatsonIsland in Miami. Photographby Joe Wasilewski.A Green Iguana (Iguanaiguana) makes itself at homeon a Coconut Palm (Cocosnucifera) in downtownMiami. Photograph by JoeWasilewski.Literature CitedBartlett, R.D. and P.P. Bartlett. 1995. Iguanas. Barron’s EducationalSeries, Hauppauge, New York. 88 pp.Bartlett, R.D. and P.P. Bartlett. 1999. A Field Guide to FloridaReptiles and Amphibians. Gulf Publishing Company, Houston,Texas. 280 pp.Butterfield, B.P., W.E. Meshaka, Jr., and C. Guyer. 1997.Nonindigenous amphibians and reptiles, pp.123–138. In: D.Simberloff, D. C. Schmitz, and T. C. Brown (eds.), Strangers inParadise: Impact and Management of Nonindigenous Speciesin Florida. Island Press, Washington, D.C.Carr, A.F., Jr. 1940. A contribution to the herpetology of Florida.University of Florida Publications, Biological Sciences 3:1–118.Cope, E.D. 1863. On Trachycephalus, Scaphiopus, and otherAmerican Batrachia. Proceedings of the Academy of NaturalSciences of Philadelphia 15:43–54. Duellman, W.E. and A. Schwartz. 1958. Amphibians and reptilesof southern Florida. Bulletin of the Florida State Museum,Biological Sciences 3:181–324.Eggert, J. 1978. The invasion of the Wish Willy. Florida Wildlife31(5):9–10.Frost, D.R., R. Etheridge, D. Janies, and T.A. Titus. 2001. Totalevidence, sequence alignment, evolution of polychrotid lizards,and a reclassification of the Iguania (Squamata: Iguania).American Museum Novitates (3343):1–38.Garman, S. 1887. On West Indian reptiles. Iguanidæ. Bulletin of theEssex Institute 19:1–26.Hoover, C. 1998. The U.S. Role in the International Live ReptileTrade: Amazon Tree Boas to Zululand Dwarf Chameleons.TRAFFIC North America, Washington, D.C. 59 pp.King, F. W. and T. Krakauer. 1966. The exotic herpetofauna ofsoutheast Florida. Quarterly Journal of the Florida Academy ofSciences 29:144–154.Köhler, G. 2002. Schwarzleguane. Lebensweise, Pflege, Zucht.Herpeton, Offenbach. 142 pp.Köhler, G. and B. Streit. 1996. Notes on the systematic status oftaxa acanthura, pectinata, and similis of the genus Ctenosaura(Reptilia: Sauria: Iguanidae). Senckenbergiana Biologica75:33–43.Krysko, K.L., K.M. Enge, J.H. Townsend, E.M. Langan, S.A.Johnson, and T.S. Campbell. In press. New county records ofamphibians and reptiles from Florida. Herpetological Review.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 66:74–79.McCoid, M.J. 2002. Geographic distribution: Ctenosaura pectinata.Herpetological Review 33:321.McKeown, S. 1996. A Field Guide to Amphibians and Reptiles inthe Hawaiian Islands. Diamond Head Publishing, Los Osos,California. 172 pp. McKercher, E. 2001. Ctenosaura pectinata (Iguanidae) on GasparillaIsland, Florida: colonization, habitat use and interactions withGopherus polyphemus. M.S. Thesis, University of Florida,Gainesville, Florida. 117 pp.Meshaka, W.E., Jr., W.F. Loftus, and T. Steiner. 2000. The her-petofauna of Everglades National Park. Florida Scientist63:84–103.Townsend, J.H., K.L. Krysko, and K.M. Enge. 2003. The identityof Spiny-tailed Iguanas, Ctenosaura, introduced to Florida, USA.Herpetozoa 16:67–72.Townsend, J.H., K.L. Krysko, A.T. Reppas, and C.M. Sheehy III.2002. Noteworthy records of introduced reptiles and amphib-ians from Florida, USA. Herpetological Review 33:75.Wilson, L.D. and L. Porras. 1983. The ecological impact of man onthe south Florida herpetofauna. University of Kansas Museumof Natural History, Special Publication (9):vi + 89 pp.118 IGUANA Volume 10, Number 4A Green Iguana (Iguanaiguana) shares the shorelinewith White Ibises (Eudocimusalbus) in a Miami park.Photograph by Joe Burgess.Green Iguanas, such asthis juvenile, are acommon sight in andaround the ColobusMonkey exhibit at theMiami Zoo. Photographby Carole Saucier.

Introduced Iguanas in Southern Florida: A History of More Than 35 Years

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Introduced Iguanas in Southern Florida: A History of More Than 35 Years

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