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272 IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 PERRY, POWELL, AND WATSON

Puerto Rican Bank endemic species like this Saddled Anole (Anolis  stratulus) are found on nearly all of the islands in the region. However,
transporting even native species from island to island may dilute unique gene pools that have evolved on individual islands that have
been separated for thousands of years.

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Only habitat loss is a bigger threat to native species than
invasive species, which are found in increasing numbers in

both terrestrial and aquatic habitats and cause over $100 billion
in estimated economic damage every year in the United States
alone (Pimentel et al. 2000). Such species often arrive via the
transportation network (reviewed in Ruiz and Carlton 2003),
whether voluntarily (intentional introductions) or involuntarily
(accidental immigrants). That has been the case of the Cuban
Treefrog (CTF), Osteopilus septentrionalis, which has been
spreading in the Caribbean, primarily as a stowaway in orna-
mental plants and construction materials (e.g., Townsend et al.
2000, Powell et al. 2005, Powell 2006). In recent years, one of
us has documented its ongoing expansion in the British Virgin
Islands (BVI), where it is now known from breeding populations
on Tortola, Virgin Gorda, Beef Island, and Peter Island (Owen
et al. 2005, 2006). Single individuals have been documented on
Necker Island and Guana Island, but searches of both in 2006
revealed no breeding populations, adults, or tadpoles. This frog
is of concern for several reasons: It appears to cause the decline
of native frogs, at least partially by direct predation; it also feeds
on lizards, snakes, birds, and — primarily — invertebrates. In
addition, it invades the water cisterns that are the main source
of drinking water for many BVI residents, raising human health
concerns.

Even before the collection of a CTF on Guana Island, a pri-
vate wildlife preserve, the owners and management have been
committed to keeping these frogs off the island. Over the years,
they have fumigated plants and construction materials with
vehicle exhaust, but the frogs appear remarkably resistant to long
exposures to the toxic fumes, and this practice has been stopped.
Nursery staff is supposed to inspect all plants for frogs before
loading. In addition, all arriving nursery and construction mate-
rials are individually inspected before they are allowed onto the
island. So far, these searches have resulted in the capture and
destruction of three CTFs, two in a single shipment in 2005 (S.
Western, pers. comm.) and one in 2004 (H. Watson, unpub-
lished). Here, we report on one such search.

On 12 October 2006, the barge Deriece-W, normally
based on Beef Island, delivered over 220 potted plants to Guana
Island: Ficus microcarpa, Clusia guttifera, Bougainvillea “Helen
Johnson,” Pandanus utilis, Jatropha integerrima, Suriana mar-
itima (Bay Cedar), and Coccoloba uvifera (Seagrape). As with
many ornamental plants used throughout the Caribbean, they
originated in Florida, USA, which is inundated with invasive
reptiles and amphibians (e.g., Meshaka et al. 2004). Prior to
being loaded on the barge, plants were housed at Minine’s
Plants, a nursery on Beef Island that is heavily infested with
CTFs (Owen, 2005). Some of the material (Clusia and Jatropha)
had arrived from Florida 10 days previously, while other plants
had been on Beef Island for up to 18 months. In addition to the
plants, the barge carried soil and several vehicles, including a
truck loaded with additional plants. Thus, we were concerned
about both frogs (either arriving directly from Florida or
acquired at the nursery) and other organisms that might have
arrived from either location. One species of particular concern
was the Brown Anole, Anolis sagrei, which also has invaded
Florida and is spreading in the Caribbean (e.g., Greene et al.
2002, Henderson and Powell 2005), often to the detriment of
native species (Kolbe et al. 2004). So far, it has not been found
in the BVI. The search was conducted by a team of eight,
including the authors, and lasted approximately one hour. Each
plant was individually searched, with both foliage and soil being
sifted for invasive organisms. Those found were recorded and
removed.

We removed from the plants inspected five juvenile anoles,
later identified as the native Crested Anole (Anolis cristatellus),

Keeping Invasive Species Off Guana Island,
British Virgin Islands

Gad Perry1, Robert Powell2, and Howard Watson3

1 Department of Natural Resource Management, Texas Tech University, Box 42125, Lubbock, Texas 79409-2125, USA (email: Gad.Perry@TTU.edu).
2 Department of Biology, Avila University, Kansas City, Missouri 64145, USA.

3 Guana Island, British Virgin Islands.

IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 273INVASIVE SPECIES ON GUANA ISLAND

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A Cuban Treefrog (Osteopilus septentrionalis) on an ornamental plant
at the Beef Island nursery.



274 IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 PERRY, POWELL, AND WATSON

A cistern on Beef Island, the source of water for a household, is teeming with dozens of Cuban Treefrogs (Osteopilus septentrionalis).

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Guana Island, like the many other islands of various sizes that comprise the British Virgin Islands, is separated from other islands only by short dis-
tances across intervening channels. As part of the Greater Puerto Rico Bank, these islands were once connected when sea levels were much lower
than today. At least those populations of plants and animals with limited abilities to disperse across water have evolved separately on individual
islands, and efforts should be made to avoid diluting potentially unique gene pools by transferring even common species from island to island.

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IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 275INVASIVE SPECIES ON GUANA ISLAND

and sighted at least one other that was not recovered. In the soil
of the planters, we collected one dwarf gecko, later identified as
a native Sphaerodactylus macrolepis. In addition, we recovered
one immature spider (an unidentified member of the genus
Selenops; catalog number TTU-Z 31,098) and three individual
snails, Zachrysia provisoria (MCZ 356974). This species origi-
nates in Cuba, but has been reported in Florida and elsewhere
in the Caribbean, including the U.S. Virgin Islands (A.
Baldinger, pers. comm.; Kraus 2005). The soil in two pots con-
tained nests of the imported Red Fire Ant (Solenopsis invicta),
and had to be fumigated. This species is not listed among those

The barge, with its gate down, is ready to disgorge its load of plants
and soil on Guana Island.

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The Cuban Brown Anole (Anolis sagrei) is an aggressive invader originat-
ing in Cuba. These lizards thrive in habitats altered by human activity.

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James Lazell and Howard Watson inspecting the leaf axils of Pandanus utilis for stowaways.



located by Miller (1994), who searched a similar barge at the
same location, but looked for invertebrates.

In addition to these cargo-related species, we recovered two
juvenile ground lizards, later identified as the native Ameiva

exsul, which appeared to have been resident on the barge. When
chased, the lizards behaved in a manner we have never previ-
ously encountered or seen described. Both lizards used a drain
hole on the edge of the deck to launch themselves into the sea,
about 3 meters below. Once in the water, they swam as a croc-
odile or marine iguana would, tucking their limbs against their
bodies and undulating the body and tail. Swimming occurred
both under and on the surface of the water and lasted about 1
minute in each case. The lizards then swam back to the boat and
climbed up its side. This ability may help explain why ground
lizards are found on so many islands. We are happy to report
that the owners of Guana Island, in keeping with their long-
term policy of protecting the island, have now decided to sus-
pend such shipments.

None of the reptiles collected were invasives, nor were
CTFs found during our search, but some of the invertebrates
collected were, similar to the findings of Miller (1994). Both the
number of organisms discovered on this barge and their diver-
sity is alarming for two reasons. First, they indicate that a broad
range of organisms can and is transported in such shipments,
which are not uncommon. In the last few years, Guana Island,
which is not a major consumer of nursery plants, typically
received 2–3 shipments of similar magnitude a year, as well as
several smaller ones (H. Watson, unpublished). The potential
for arrival of invasive species, such as the Fire Ants (already estab-
lished on Guana) or CTF (which has not been noted this year,
despite repeated surveys of all freshwater locations on the island)
is alarmingly high. Second, transporting native species between

276 IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 PERRY, POWELL, AND WATSON

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This dwarf gecko, Sphaerodactylus macrolepis, is common in the British Virgin Islands.

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A juvenile Crested Anole (Anolis cristatellus) on a nursery plant on top
of a truck loaded on the barge. The animal escaped before it could be
captured.



IGUANA  •  VOLUME 13, NUMBER 4  •  DECEMBER 2006 277INVASIVE SPECIES ON GUANA ISLAND

islands is not a benign activity. It swamps local genetic special-
izations that have evolved after the islands separated, leaving
populations less well-adapted to local conditions. For example,
water loss rates vary among islands in a manner related to their
aridity (Dmi’el et al. 1997), and this variation has at least some
genetic basis (Perry et al. 2000). Bringing in foreign genetic
material could make an island population less capable of surviv-
ing a drought. In addition, such translocations make research
into the biological history of the islands much more difficult.
For example, an ongoing study of the genetic differences among
Crested Anole populations and their relationship to other bio-
geographic patterns would be severely hampered if animals are
regularly transported among islands.

BVI law offers little guidance about inspecting and sanitiz-
ing shipments arriving from other locations, such as Florida. We
support the recommendation of Perry and Gerber (2006) that
additional measures are needed to prevent the arrival of invasive
species and eradicate those already in the BVI. In addition, how-
ever, we also recommend that internal biosecurity measures be
established to reduce the risk of native species being accidentally
moved among islands. Such measures are clearly needed to
reduce the spread of invasives already found in the BVI, such as
the Fire Ant or CTF, to new locations. We are not aware of such

regulations being in effect in any island-based nation. Attempts
at quarantines of mainland invasives, such as the Fire Ant in the
USA, often have failed because the volume of transport is high
and inspection is lax, but the isolation provided by an island-
based system offers some hope of success.

Acknowledgements
We thank B. Best, C. Boal, J. Lazell, S. Valentine, and T. Willard
for assistance in inspecting the cargo, and J. Cokendolpher and
A. Baldinger for identifying the invertebrates. Financial support
for this work was provided by The Conservation Agency
through a grant from the Falconwood Foundation. This is man-
uscript T-9-1117 of the College of Agricultural Sciences and
Natural Resources, Texas Tech University.

References
Dmi’el, R., G. Perry, and J. Lazell. 1997. Evaporative water loss in nine insu-

lar lizard populations of the Anolis cristatellus group in the British Virgin
Islands. Biotropica 29:111–116.

Greene, B.T., D.T. Yorks, J.S. Parmerlee, Jr., R. Powell, and R.W. Henderson.
2002. Discovery of Anolis sagrei in Grenada with comments on its poten-
tial impact on native anoles. Caribbean Journal of Science 38:270–272.

Henderson, R.W. and R. Powell. 2005. Geographic distribution: Anolis sagrei.
Herpetological Review 36:467.

Kolbe, J.J., R.E. Glor, L. Rodríguez Schettino, A.C. Lara, A. Larson, and J.B.
Losos. 2004. Genetic variation increases during biological invasion by a
Cuban lizard. Nature 431:177–181.

Kraus, F. 2005. The land snails, pp. 247–249. In: J. Lazell (ed.), Island: Fact
and Theory in Nature. University of California Press, Berkeley.

Meshaka, W.E., Jr., B.P. Butterfield, and J.B Hauge. 2004. Exotic Amphibians
and Reptiles of Florida. Krieger Publishing Company, Melbourne, Florida.

Miller, S.E. 1994. Dispersal of plant pests into the Virgin Islands. Florida
Entomologist 77:520–521.

Owen, J. 2005. The Cuban Tree Frog: Distribution, Diet, and Reproduction
of an Invasive Species in the BVI. Unpublished M.S. Thesis, Texas Tech
University, Lubbock.

Owen, J., G. Perry, J. Lazell, and J. Egelhoff. 2005. Osteopilus septentrionalis
(Cuban Tree Frog). Distribution. Herpetological Review 36:76. 

Owen, J., G. Perry, J. Lazell, C. Petrovic, and J. Egelhoff. 2006. Osteopilus
septentrionalis (Cuban Tree Frog). Colonization of the British Virgin
Islands. Herpetological Review 37:74–75. 

Perry, G., R. Dmi’el, and J. Lazell. 2000. Evaporative water loss in insular pop-
ulations of Anolis cristatellus (Reptilia: Sauria) in the British Virgin Islands
III: A common garden experiment. Biotropica 32:722–728.

Perry, G. and G.P. Gerber. 2006. Conservation of amphibians and reptiles in
the British Virgin Islands: Status and patterns. Applied Herpetology
3:237–256.

Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and
economic costs associated with non-indigenous species in the United
States. BioScience 50:53–65.

Powell, R. 2006. Conservation of the herpetofauna on the Dutch Windward
Islands: St. Eustatius, Saba, and St. Maarten. Applied Herpetology
3:293–306.

Powell, R., R.W. Henderson, and J.S. Parmerlee, Jr. 2005. Reptiles and
Amphibians of the Dutch Caribbean: St. Eustatius, Saba, and St. Maarten.
St. Eustatius National Parks Foundation, Gallows Bay, St. Eustatius,
Netherlands Antilles.

Ruiz, G.M. and J.T Carlton. 2003. Invasion vectors: A conceptual framework
for management, pp. 459–504. In: G. M. Ruiz and J.T. Carlton (eds.),
Invasive Species: Vectors and Management Strategies. Island Press,
Washington.

Townsend, J.H., J.M. Eaton, R. Powell, J.S. Parmerlee, Jr., and R.W.
Henderson. 2000. Cuban Treefrogs (Osteopilus septentrionalis) in
Anguilla, Lesser Antilles. Caribbean Journal of Science 36:326–328.

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Ameiva exsul swimming in the sea after leaping from the deck of the
barge.

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One of two juvenile ground lizards (Ameiva exsul) encountered on the
barge.




