Rice, Kenneth G. and Waddle, J. Hardin and Crockett, Marquette E. and Carthy, Raymond R. and Percival, H. Franklin
Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume II. Virgin Islands National Park.
U.S. Geological Survey,
(Open File Report - U.S. Geological Survey,2500-1301)
Amphibian declines and extinctions have been documented around the world, often in protected
natural areas. Concern for this alarming trend has focused attention on the need to document all species of
amphibians that occur within U.S. National Parks and to search for any signs that amphibians may be
declining. This study, an inventory of amphibian species in Virgin Islands National Park, was conducted
from 2001 to 2003. The goals of the project were to create a georeferenced inventory of amphibian
species, use new analytical techniques to estimate proportion of sites occupied by each species, look for
any signs of amphibian decline (missing species, disease, die-offs, etc.), and to establish a protocol that
could be used for future monitoring efforts.
Several sampling methods were used to accomplish these goals. Visual encounter surveys and
anuran vocalization surveys were conducted in all habitats throughout the park to estimate the proportion
of sites or proportion of area occupied (PAO) by amphibian species in each habitat. Line transect methods
were used to estimate density of some amphibian species and double observer analysis was used to refine
counts based on detection probabilities. Opportunistic collections were used to augment the visual
encounter methods for rare species. Data were collected during four sampling periods and every major
trail system throughout the park was surveyed.
All of the amphibian species believed to occur on St. John were detected during these surveys.
One species not previously reported, the Cuban treefrog (Osteopilus septentrionalis), was also added to
the species list. That species and two others (Eleutherodactylus coqui and Eleutherodactylus lentus) bring
the total number of introduced amphibians on St. John to three. We detected most of the reptile species
thought to occur on St. John, but our methods were less suitable for reptiles compared to amphibians.
No amphibian species appear to be in decline at this time. We found no evidence of disease or of
malformations. Our surveys provide a snapshot picture of the status of the amphibian species, so
continued monitoring would be necessary to determine long-term trends, but several potential threats to
amphibians were identified. Invasive species, especially the Cuban treefrog, have the potential to decrease
populations of native amphibians. Introduced mammalian predators are also a potential threat, especially
to the reptiles of St. John, and mammalian grazers might have indirect effects on amphibians and reptiles
through habitat modification. Finally, loss of habitat to development outside the park boundary could
harm some important populations of amphibians and reptiles on the island.
Monograph or Serial Issue
||Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume II. Virgin Islands National Park
|Rice, Kenneth G.|
|Waddle, J. Hardin|
|Crockett, Marquette E.|
|Carthy, Raymond R.|
|Percival, H. Franklin|
||Open File Report - U.S. Geological Survey
|Number of Pages:
||U.S. Geological Survey
|Place of Publication:
||Florida Cooperative Fish and Wildlife Research Unit
|| This document was submitted by the Florida Cooperative Fish and Wildlife Research Unit. Revised and reprinted 2005
||Virgin Islands National Park; amphibians; survey; National Parks; reptiles
||27 May 2011 14:05
||29 Sep 2011 15:26
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