Florida has the largest
number of non-native amphibian and reptile species in the United States
(Butterfield et al., 1997). Its diverse habitats and suitable climates
from the subtropical southern peninsula and Florida Keys north to the
subtemperate panhandle have facilitated exotics in becoming established
and expanding their ranges. While conducting surveys in the southern
peninsula and Florida Keys over the last decade, we have uncovered numerous
geographic distributional records, misidentified species, and new exotic
species with established populations (Krysko and Decker, 1996; Reppas
et al., 1999; Krysko et al., 2000; Krysko and King, 2002; Townsend et
al., 2002; Krysko et al., 2003). Herein, we report four established
populations of the Madagascar giant day gecko, Phelsuma madagascariensis
grandis Gray 1870, in the Florida Keys, Monroe County.Methods
Records of Phelsuma madagascariensis grandis
are based on captures and observations during six survey days in
the Florida Keys in 2002: 3 March; 3, 5, 7–8 May; and 8 August. Additional
records were acquired based on observations by colleagues. Because this
gecko species is diurnal (Henkel and Schmidt, 2000), searches were conducted
during the daytime. Dorsal patterns are unique for each individual,
and an attempt was made to photograph, estimate total length (TL), and
note location of each individual for identification purposes. Only individuals
that could be distinguished from others were counted in our overall
total. We divided size classes into six categories based on estimated
TL, including <8 cm (hatchling), 8–11 cm, 12–16 cm, 17–20 cm, and >20
cm (adult). Gender was distinguished in adults by the noticeable presence
or absence of endolymphatic chalk sacs, which are used for calcium metabolism
and egg shell formation in females (Tytle, 1992). Captures were made
by hand, and voucher specimens and photographs were deposited in the
Florida Museum of Natural History (FLMNH), University of Florida (UF
collection).
Table1: Estimated size classes and UF voucher
specimens and photographs of Madagascar giant
day geckos (Phelsuma madagascariensis grandis) we recorded in
2002 on Little Torch Key and Grassy Key, Monroe County, Florida. Note
that adults are >20 cm TL, and individuals with no UF # were neither
photographed nor collected.
Results
We recorded 32 Phelsuma madagascariensis grandis
on Little Torch Key and Grassy Key. Numerous individuals were also
recorded on Grassy Key (McCleary, 2002), Big Pine Key (Decker, 2002;
pers. obs.) and Plantation Key (Kavney, 2002).
Between 3 March–8 August 2002, we recorded 29 P. m. grandis consisting
of both genders and all age classes on Little Torch Key (24°39.944’N,
81°23.411’W) (Table 1). Individuals were frequently seen on white mangrove
(Laguncularia racemosa) and buttonwood (Conocarpus erectus) trees,
buildings, and bird cages bordering mangrove-lined estuaries.
On 3 May 2002, we recorded two adult females and one adult male on the
confluence of a gumbo limbo tree (Bursera simaruba) and telephone
post in the parking lot of the Dolphin Marine Research Center on Grassy
Key (24°46.260’N, 80°56.433’W) (Table 1). Additionally, on 14 June 2002
four juveniles (6 cm, 7.5 cm, two 9 cm TL) were observed in the shade
of bushes and trees on these premises (McCleary, 2002). These individuals
were not collected. In August 2001, three individuals were observed
on buildings and wooden fences near Cunningham Lane just N of U.S. 1
on Big Pine Key (24°40.250’N, 81°21.336’W) (Decker, 2002). We verified
one of these individuals as an adult female. The other two individuals
were not collected. Another adult was observed basking on a utility
pole at the junction of U.S. 1 and Wilder Road (Kavney, 2002). We have
also observed numerous individuals being sold in a local pet store that
were reportedly collected locally.
In September 2002, eight newborns to adults of both genders were collected
and numerous others were observed near the Indian Mound on Plantation
Key (24°59.270’N, 80°33.021’W) (Kavney, 2002).
Discussion
Phelsuma madagascariensis grandis was first reported from Hollywood,
Broward County (Bartlett and Bartlett, 1999). These geckos were released
or had escaped from a nearby reptile importer in the early 1990s, but
never represented an established population. No voucher specimens were
ever taken and no individuals were seen after numerous surveys of the
area (Decker, 2002). We know of other intentional releases of this species
in Miami-Dade County, but these individuals are not known to be reproducing.
The closest population we identified (Grassy Key) exists ca. 240 km
SW of the Broward County report, and our data provide evidence of the
first verified established populations of P. m. grandis in the United
States.
The population of Phelsuma madagascariensis grandis on Little
Torch Key appears to have originated from a single introduction. This
species was likely introduced onto this island by an exotic animal hobbyist
as geckos were frequently seen on buildings and exotic bird cages.
Phelsuma m. grandis on Big Pine Key appears to have originated
from a single source. A resident of the island released this species
in certain areas for subsequent harvesting (Decker, 2002) as their offspring
are collected and sold for resale at a local pet store. Phelsuma
m. grandis on Grassy Key and Plantation Key were introduced onto
both islands independently by different local residents.
Phelsuma madagascariensis grandis feeds primarily on nectar and
arthropods (Demeter, 1976; Tytle, 1992), but congeners have also been
documented feeding on Hemidactylus geckos (García and Vences,
2002). The tropical house gecko (Hemidactylus mabouia) was first
reported introduced on Crawl Key (Lawson et al., 1991), and presently
this species is probably the most abundant terrestrial vertebrate in
the Florida Keys and may prove to be a food source for P. m. grandis.
On 7 May 2002, an adult P. m. grandis was observed feeding on
insects up until ca. 30 min after dark, upon which the gecko retreated
into a crack on a wooden building on Little Torch Key. Some individuals
on Little Torch Key were seen in the same vicinity on every survey day,
suggesting that this species might be territorial like other Phelsuma
species (McKeown, 1993). Phelsuma m. grandis have been known
to live for > 20 years in captivity (McKeown, 1993). Tytle (1992) reported
a captive female ovipositing 27 eggs in one year, and during a nine-year
span one captive female produced 68 clutches consisting of 120 eggs
(Krysko, pers. obs.). This species is a non-gluer (i.e., oviposited
eggs are not affixed to a substrate) (Osadnik, 1984), and its eggs are
usually oviposited in pairs (Demeter, 1976; Osadnik, 1984; Tytle, 1992)
within crevices, between strong leaves, or in the ground (Osadnik, 1984).
Longevity, high fecundity, and abundance of prey are factors likely
to facilitate population increases and range expansion of P. m. grandis
in the Florida Keys. Population monitoring, documentation of ecological
impacts on Florida’s native flora and fauna, and/or eradication efforts
should be conducted.
Acknowledgements
We would like to thank Sean W. Morey (FLMNH) for field
assistance; Frank and Susan Morey for accommodations in the lower Florida
Keys; John N. Decker, Jim Kavney, Sean O’Donnell, Ryan J. R. McCleary,
and Bob Ehrig for Phelsuma information in the Florida Keys.
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