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R
esearchers 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, Eleutherodactylus
planirostris (Cope), from southern Florida, and
the report of Anolis sagrei followed about 25 years
later (Garman 1887). Since then, numerous papers
have detailed the introduced herpetofauna of
southern Florida (e.g., Carr 1940, Duellman and
Schwartz 1958, King and Krakauer 1966, Wilson
and Porras 1983, Butterfield et al. 1997), and
more than 40 non-native species are presently
reported. These reptiles and amphibians were ini-
tially introduced and their populations are supple-
mented via various routes. Some of these exotics
may find their way into the suitable climate of
southern Florida as stowaways in shipments of
ornamental plants and other commerce, but many
recent introductions can be attributed to individ-
Introduced Iguanas in
Southern Florida: A History
of More Than 35 Years
Josiah H. Townsend
1
, Kenneth L. Krysko
1
, and Kevin M. Enge
2
1
Division of Herpetology, Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611-7800
2
Florida Fish and Wildlife Conservation Commission, Joe Budd Wildlife Field Office, 5300 High Bridge Road,
Quincy, Florida 32351
All photographs are by the senior author except where noted.
111
IGUANA
December 2003
Adult 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 escaping
from reptile dealers or pet owners. As the trade in
reptiles and amphibians has increased, so has the
number of exotic species that have become estab-
lished. Some of the more notable, and noticeable,
of these species are three large lizards in the family
Iguanidae (sensu Frost et al. 2001): the Mexican
Spiny-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 or
Ctenosaurs. They are large iguanids that typically
have tails ringed with rows of enlarged, spiny
scales. Presently, 17 species are recognized.
Ctenosaurs are found in southern Baja California,
its offshore islands, and on mainland Central
America from adjacent parts of Mexico to Panama
(Köhler 2002; see also IGUANA 10(2):56–57
and 10(3):79–81). Two of these species, C. pecti-
nata and C. similis, are known to be established in
southern Florida.
Ctenosaura pectinata is native to the Pacific
versant of southern Mexico. This species was first
reported in Florida by Eggert (1978), who
described digging up eggs and observing adults
near 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 first
in a series of misidentifications involving intro-
duced Ctenosaurs in Florida, as C. pectinata was
subsequently reported from Key Biscayne
(Butterfield et al. 1997), Gasparilla Island (Bartlett
and Bartlett 1999, McKercher 2001, McCoid
2002), and from “… the streets and trees of met-
ropolitan Miami” (Bartlett and Bartlett 1999).
After examining all Florida specimens of
Ctenosaura in systematic collections and collecting
specimens from all known localities in southern
Florida, Townsend et al. (2003) concluded that
most populations (including those known from
Key Biscayne and Gasparilla Island) are C. similis,
and the only extant population of C. pectinata
occurs near the original Old Cutler Road site. We
visited the Old Cutler Road site at least six times
from 2002–2003 and observed two adult males,
six adult females, and one subadult of unknown
sex living on and adjacent to a single private prop-
erty east of Old Cutler Road between SW 168
th
and SW 184
th
streets. No other C. pectinata was
seen, and local residents with whom we talked
were unfamiliar with the lizards and unaware of
their presence. However, one resident of the
Florida Keys related that she had observed
Ctenosaurs crossing Old Cutler Road while dri-
ving through the area in 2002 and 2003 (H.
Kavney, pers. comm.).
Ctenosaura similis is native to Central
America, and is found from the Isthmus of
Tehuantepec to northeastern Nicaragua and west-
112
IGUANA
Volume 10, Number 4
Three species of iguanas have become established in
southern Florida: Ctenosaura pectinata, from near Old
Cutler Road (top), southeastern Miami-Dade County, and
adult male Ctenosaura similis (middle), and Iguana iguana
from Key Biscayne (bottom).
ern Panama on the respective Atlantic and Pacific
versants. The extent to which C. similis has
become established in southern Florida is only
now becoming clear. One of the earliest known
populations of C. similis in Florida occurs on Key
Biscayne. That population probably has persisted
there since at least 1979, when the Crandon Park
Zoo was closed and most of the exhibit animals
were relocated to the Miami Metrozoo
(Townsend et al. 2003). Since its introduction on
Key Biscayne, C. similis has become well-estab-
lished in Crandon Park and is being found in
increasing numbers in Bill Baggs Cape Florida
State Park at the southern end of Key Biscayne (E.
Donlan and E. Golden, pers. comm.). This
species also was introduced on Gasparilla Island,
Charlotte and Lee counties, on Florida’s south-
western Gulf Coast during the late 1970s or early
1980s, when an island resident released as few as
three individuals brought back from Mexico
(Krysko et al. 2003). Ctenosaura similis now
occurs on Gasparilla Island in large numbers and
has expanded its range onto the adjacent main-
land and onto Cayo Costa, a small island south of
Gasparilla Island. Large populations also occur on
Keewaydin and Little Marco islands and within
the boundaries of the Rookery Bay Estuarine
Research Reserve, Collier County. The latter pop-
ulation was established in 1995, when a
Keewaydin resident intentionally (and illegally)
released 5–30 C. similis on his property (Krysko
et al. 2003). The deliberate introduction of non-
native reptiles is illegal according to Florida
Statute 372.265, which specifically prohibits the
release of exotic wildlife without a permit from
the Florida Fish and Wildlife Conservation
Commission.
Confusion regarding the identities of southern
Florida’s Ctenosaurs may be attributed partially to
a general similarity in the appearance of the two
species. As adults, both C. pectinata and C. similis
are large, dark-colored terrestrial lizards that may
113
IGUANA
December 2003
Map of South Florida showing localities mentioned in the article.
appear striped or banded. Juveniles of both species
are green at the time of hatching, gradually taking
on the brown or black adult coloration as they
mature. However, these two species may be dis-
tinguished easily by using a few morphological
characters 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 4–12
well-defined dark dorsal bands that extend nearly
to the ventral scales. Male C. similis also may take
on an orange color around the head and throat
during the breeding season. In contrast, mature C.
pectinata have a black to brown ground color
marked with irregular whitish blotches, with addi-
tional white coloration usually apparent in the area
of the neck and throat. These white markings may
give C. pectinata a partially banded appearance.
Both C. similis and C. pectinata have tails that are
ringed with rows of enlarged spiny scales, or
whorls, that are separated by smaller smooth scales,
or intercalaries — but differ in the number of
intercalaries that separate the whorls. This is most
apparent 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 three
rows of intercalaries. Florida C. similis also tend to
have very few (usually zero) small dorsal scales
between the posterior end of the dorsal crest and
the anterior end of the caudal crest, whereas
Florida C. pectinata usually has 7 or 8 (range
0–20) dorsal scales between crests (Townsend et
al. 2003).
Currently, C. pectinata appears to be restricted
to a single small area around Old Cutler Road, and
occurs in low numbers there despite having been
introduced at least 25 years ago. Expansion of this
population may have been limited by natural and
man-made geographic barriers, including a canal
to the north, construction in the early 1980s of a
large corporate headquarters to the south,
114
IGUANA
Volume 10, Number 4
Adult female (right) and an adult male and
female (below) Ctenosaura pectinata near Old
Cutler Road, southeastern Miami-Dade County.
(below) Adult male
Ctenosaura similis,
Key Biscayne.
Biscayne Bay to the east, and Old Cutler Road to
the west. A large area directly to the south of the
current population was developed since the time it
was reported by Wilson and Porras (1983), a
process which may have reduced the numbers of
C. pectinata to the low numbers seen today. In
contrast, C. similis has been an exceedingly suc-
cessful invader, becoming well-established and
expanding its range in a number of Florida locali-
ties. Site fidelity associated with Ctenosaura uti-
lization of holes or other refugia may slow the
process of range expansion beyond the original site
of introduction. Nonetheless, neither species of
Ctenosaura has been nearly as successful as an
invader as their familiar relative, the Green or
Common Iguana (Iguana iguana).
Iguana iguana is one of the most popular rep-
tiles in the pet trade, with over 1.14 million
imported into the United States in 1995 alone,
and represents about 45% of all reptilian imports
(Hoover 1998). Iguana iguana has a wide native
range and is found at low elevations on the main-
land from Sinaloa, Mexico south to Ecuador on
the Pacific versant and Veracruz, Mexico to south-
ern Brazil on the Atlantic versant, as well as on
some Central and South American coastal islands
115
IGUANA
December 2003
Juvenile 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 United
States, I. iguana has been introduced in southern
Florida and Hawaii (McKeown 1996). Iguana
iguana was first reported in southern Florida by
King and Krakauer (1966), who indicated that
iguanas could be found on Key Biscayne, Hialeah,
Coral Gables, and near the Miami International
Airport. Iguana iguana has since become estab-
lished at least as far north as Palm Beach County
on the Atlantic Coast and Lee County on the Gulf
Coast (Bartlett 1980, Bartlett and Bartlett 1999,
Townsend et al. 2002, Krysko et al. in press), and
as far south as Stock Island in the Florida Keys,
Monroe County. In all likelihood, this species is
much more abundant in southern Florida than
previously reported in the literature. The largest
populations of I. iguana probably occur in eastern
Miami-Dade County on Key Biscayne, in Fairchild
Tropical Garden, and Matheson Hammock Park,
but these lizards are now found at localities
throughout the county and have been sighted
numerous times in Everglades National Park
(Meshaka et al. 2000).
In Florida, I. iguana usually is found near
water, often in trees or on embankments border-
ing canals and lakes, or even basking on lawns or
pavement in urban and suburban areas. Juveniles
and adults are strictly
herbivorous. In
Florida, iguanas eat a
wide variety of both
exotic ornamentals and
native plants (see
IGUANA
10(3):94–95). Iguana
iguana on Key
Biscayne nests in sandy
areas, often with multi-
ple females utilizing a
single small area. Most hatchlings appear during
July and August. Relatively few predators of juve-
niles occur in the urban and suburban areas of
southern Florida, a factor that may lead to rapid
growth in any introduced I. iguana population
that contains multiple reproducing females. Lack
of predators and abundance of food are some of
the primary explanations for the very high popula-
tion densities of I. iguana found in southern
Florida.
Bill Baggs Cape Florida State Park (CFSP)
occupies 174 ha at the southern end of Key
Biscayne, almost all of it consisting of coastal
strand habitat dominated by Saw Palmetto
(Serenoa repens) or coastal hammock dominated by
Buttonwood (Conocarpus erectus) and Sea Grape
(Coccoloba uvifera). In 2003 alone, CFSP staff
removed over 500 Green Iguanas (E. Donlan,
pers. comm.). However, thousands of iguanas live
on Key Biscayne outside of CFSP, and, when an
I. iguana is removed from the grounds of CFSP,
other iguanas from outside the park simply move
in and take up available space. Low winter tem-
peratures appear to be a major factor limiting the
northern expansion of I. iguana in Florida; how-
ever, a freeze in Miami-Dade County during the
winter of 2002–2003 did little more than tem-
116
IGUANA
Volume 10, Number 4
An obviously gravid female Iguana iguana pauses while
excavating her nest at Key Biscayne. Photographs by Esther
M. Langan.
porarily reduce numbers (see IGUANA
10(3):98). Interestingly, many I. iguana have
learned to seek shelter in burrows or under build-
ings, and we have observed I. iguana taking
refuge under water, exposing only their snouts for
breathing, to escape extremely cold temperatures.
Another large iguanid, the Hispaniolan
Rhinoceros Iguana or Cyclura cornuta
(Bonnaterre), was reported in very small numbers
in the vicinity of the Miami Seaquarium on
Virginia Key and also possibly on Key Biscayne
(King and Krakauer 1966). A few individuals of
this species escaped from an exhibit at the
Seaquarium and are purported to have repro-
duced in small numbers (Bartlett and Bartlett
1995). However, we have not observed this
species in the wild, and no specimens from Florida
are known to have been deposited in any system-
atic collections.
With the ranges and population sizes of
Ctenosaura similis and Iguana iguana continuing
to grow and the population of C. pectinata per-
sisting for over 25 years, these species obviously
have become a permanent part of the dynamic
herpetofauna of southern Florida. These three
lizard species are only a few of the growing num-
ber of introduced reptiles and amphibians that call
southern Florida home. This number seems to be
increasing as quickly as researchers are able to
investigate each new report of a possible intro-
duced species. Without importers and pet owners
showing greater responsibility and stricter enforce-
ment of Florida state laws regarding the release of
exotic animals, what remains of the native her-
petofauna in southern Florida stands a good
chance of being displaced by exotic species in the
near future.
Acknowledgements
We thank Kevin Kirwin and Ernest Link of
Crandon Park; Elizabeth Golden and Ellen Donlan
of Bill Baggs Cape Florida State Park; Reggie
Norman, Ken Alvarez, Chris Angel, and Patty
Middleton of Gasparilla Island State Park; and
Steve Bertone of Rookery Bay Estuarine Research
Reserve for facilitating field work at their respective
parks and for providing much useful information.
Helen Kavney provided additional information.
117
IGUANA
December 2003
A Buttonwood Tree
(Cornocarpus erectus)
provides food and a place to
bask for this Green Iguana
(Iguana iguana) on Watson
Island in Miami. Photograph
by Joe Wasilewski.
A Green Iguana (Iguana
iguana) makes itself at home
on a Coconut Palm (Cocos
nucifera) in downtown
Miami. Photograph by Joe
Wasilewski.
Literature Cited
Bartlett, R.D. and P.P. Bartlett. 1995. Iguanas. Barron’s Educational
Series, Hauppauge, New York. 88 pp.
Bartlett, R.D. and P.P. Bartlett. 1999. A Field Guide to Florida
Reptiles 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 in
Paradise: Impact and Management of Nonindigenous Species
in 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 other
American Batrachia. Proceedings of the Academy of Natural
Sciences of Philadelphia 15:43–54.
Duellman, W.E. and A. Schwartz. 1958. Amphibians and reptiles
of southern Florida. Bulletin of the Florida State Museum,
Biological Sciences 3:181–324.
Eggert, J. 1978. The invasion of the Wish Willy. Florida Wildlife
31(5):9–10.
Frost, D.R., R. Etheridge, D. Janies, and T.A. Titus. 2001. Total
evidence, 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 the
Essex Institute 19:1–26.
Hoover, C. 1998. The U.S. Role in the International Live Reptile
Trade: 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 of
southeast Florida. Quarterly Journal of the Florida Academy of
Sciences 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 of
taxa acanthura, pectinata, and similis of the genus Ctenosaura
(Reptilia: Sauria: Iguanidae). Senckenbergiana Biologica
75:33–43.
Krysko, K.L., K.M. Enge, J.H. Townsend, E.M. Langan, S.A.
Johnson, and T.S. Campbell. In press. New county records of
amphibians 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 in
the Hawaiian Islands. Diamond Head Publishing, Los Osos,
California. 172 pp.
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. 117 pp.
Meshaka, W.E., Jr., W.F. Loftus, and T. Steiner. 2000. The her-
petofauna of Everglades National Park. Florida Scientist
63:84–103.
Townsend, J.H., K.L. Krysko, and K.M. Enge. 2003. The identity
of 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 on
the south Florida herpetofauna. University of Kansas Museum
of Natural History, Special Publication (9):vi + 89 pp.
118
IGUANA
Volume 10, Number 4
A Green Iguana (Iguana
iguana) shares the shoreline
with White Ibises (Eudocimus
albus) in a Miami park.
Photograph by Joe Burgess.
Green Iguanas, such as
this juvenile, are a
common sight in and
around the Colobus
Monkey exhibit at the
Miami Zoo. Photograph
by Carole Saucier.
