Jan
Meerman & Joe Garel
Introduction
South Water Caye
is a small sand caye on the barrier reef and measures only
8.2 ha (20 acres). The caye is densely inhabited and in
use by several diving operations. The dense human population
has severe impacts on the ecology of the island and much
of the island's natural vegetation has been cleared away
and replaced by housing and Coconuts (Cocos nucifera).
The island has a manicured appearance and any debris such
as fallen palm-fronds are routinely removed by burning.
Reptile fauna
Naturally occurring reptiles included the anole Anolis
(Norops) sagrei and the gecko's Aristelliger
georgeensis and Phyllodactylus tuberculosus
(Lee, 1996). During an August 1990 survey it was found that
A. georgeensis was common while P.tuberculatus appeared
scarce. Sea turtles used to nest on the island but the heavy
human use of the island has put a stop to that. A newcomer
on the island was the house-gecko Hemidactylus frenatus.
First specimens of this species were not noted in Belize
until 1993 (Meerman, pers. obs.) but this species probably
arrived in the late 1980-ies. This species has a wide distribution
in the Caribbean and "natural" colonization appears
a likely explanation for the appearance and spread of this
species. Another newcomer is the Tokay Gekko gecko.
It was probably introduced to South Water Caye somewhere
in the early 1990-ies.
The first Tokay on South Water Caye was observed in August
1994. The specimen was an adult and probably male. One year
later no less than 13 Tokays were seen including immatures,
indicating an established population. At that stage interviews
were held with people working on the caye and it was learned
that the animals were originally brought in by a tour operator
and released. Observations between 11-13 / 18-20 July 2002
revealed a total of 9 adults and one subadult. One dead
specimen was found. 3 adults were seen in buildings, the
others were in coconut palms. The palm inhabiting individuals
typically fled to the crown when approached. One huge specimen
(> 30 cm) was observed inside one of the buildings. A
single nesting aggregation was found under one of the buildings.
This aggregation contained 6 eggs and numerous hatched egg
fragments. One adult was noted beside the eggs for at least
two days (guarding, egg-laying behavior?).
Of concern is the
status of native reptiles of the South Water Caye. During
the July 2002 survey the following species were observed:
Anolis (Norops) sagrei: A total of 12 individuals
seen. Mostly on palms and fences. Appeared scarce but this
species was not the focus of searches.
Aristelliger georgeensis: Total of 6 adults + 1 juvenile
seen. Juvenile and one adult was found in head of young
coconut palm. Other adults were found in buildings. One
communal nesting site with eggs was found inside a hollow
tree.
Hemidactylus frenatus: One specimen seen on a coconut
tree, several heard.
The gecko Phyllodactylus tuberculosus could not be
reconfirmed during this visit.
Species displacement
There are indications
that the local gecko population is declining potentially
as a result of predation by the aggressive Tokay. Although
we have no exact data, we have the feeling that the number
of A. georgeenis have gone down in the past years,
also it was noted that many A. georgeenis now have
large scars and or missing tails as opposed to what was
previously noticed on the island or any other caye where
the species was observed. The originally much scarcer Phyllodactylus
tuberculosus may even have become locally extinct. At
least we have been unable to confirm this species for a
couple of years. Up to now there are no indications that
the Tokay has found it's way to other islands or even the
mainland. But when it does, it may well affect the local
herpetofauna, several species of which are regional endemics.
General Tokay
information
Tokay Gecko's are one of the largest gecko's alive today
with a length of near 35 cm (14"). The skin is usually
gray with several brownish-red to bright red spots and flecks
but it has the ability to lighten or darken the coloring
of its skin. The male is more brightly colored than the
female and generally, and also tends to be slightly larger
than the female. A conspicuous difference between the sexes
is the small amount of swelling at the base of the tail
of the male, due to the presence of the two hemipenes. Also,
the males have visible preanal and femoral pores and postanal
tubercules.
The species derives its common name from the loud mating
call of the male. This loud "to-kay"
sound is repeated multiple times (click link for call).
During the breeding period, females lay eggs about every
month. The hard-shelled eggs are affixed to a solid foundation.
Commonly several females use the same egg-laying site, as
was observed on South Water Caye.
The species has a wide distribution in South East Asia,
but has also been introduced to the USA (introduced to Florida
and probably Hawaii. In the Caribbean it appears to have
been established on Martinique.
References:
Bartlett, R. D. 1988. The geckos of Florida--notes and
comments. Notes North. Ohio Assoc. Herpetol. 16(3):2-10.
Boone, J. & B. Klusmeyer. Family Gekkonidae (Geckoes):
http://www1.embl-heidelberg.de/~uetz/families/Gekkonidae.html
Henderson etc. (1993) CARIBBEAN JOURNAL OF SCIENCE 29 (1-2):
128- 129.
King, F. W., and T. Krakauer. 1966. The exotic herpetofauna
of southeast Florida. Q. J. Fla. Acad. Sci. 29:144-154.
Lee, J. C. , 1996, The Amphibians and Reptiles of the Yucatan
Peninsula. , Comstock Publ. Assoc., Ithaca, New York.
Mckeown (1996) Field Guide Rept. Amph. Hawaiian Islands.
Stiling, P. 1989. Exotics--biological invasions. Fla. Wildl.
43(5):13-16.
Wilson, L. D., and L. Porras. 1983. The ecological impact
of man on the south Florida herpetofauna. Univ. Kansas Mus.
Nat. Hist., Spec. Publ. No. 9. 89pp.
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