Biology Reference
In-Depth Information
Islands may sometimes be able to achieve eradication and avoid reinfestation
even if the larger jurisdiction to which they belong can not achieve complete, terri-
tory-wide eradication. Such could be the case with a pending eradication attempt
against
Bufo marinus
on Viwa Island in Fiji. This 60 ha island is one of the last habi-
tats containing the endangered endemic frog
Platymantis vitiana
and the cane toads
are thought to present a threat to this species (R. Taylor and Edwards, 2005; Morley
et al., 2006). Removal of this species is part of a broader conservation plan for the
island that involves the removal of a variety of invasive mammals as well (Morley
et al., 2006). Eight ponds on the island have been fenced to exclude toads, thereby
preventing their breeding and preventing rehydration of adults during the dry season.
Another five ponds have been filled in for the same purpose. To date, the barriers
seem to be working, with no tadpoles or metamorphs found within any of the exclo-
sures (C. Morley, University of the South Pacific, personal communication, 2007).
Hence, reproduction seems to have been halted. It is intended that future efforts will
expand to include removal of adult toads by hand capture and use of traps (Morley
et al., 2006). This effort is expected to require 3-4 years to complete, if sufficient
funding can be obtained to maintain the program. Because of the small size of the
island and the fact that toad reproduction can be prevented without threatening the
direct-developing
P. vitiana
, this project is quite promising for local conservation of
native wildlife, even though cane toads will remain widespread on other islands in
Fiji. However, success is not yet assured because of funding uncertainty.
A similar situation may obtain for coqui,
Eleutherodactylus coqui
, infestations
on some islands in Hawaii, although that situation is more complicated and may
more correctly be viewed as a long-term management program. These frogs were
vectored to, from, and around Hawaii in nursery plants (Kraus et al., 1999; Kraus
and Campbell, 2002). Governmental response to the invasion was delayed until
well after Hawaii Island became widely and heavily infested (Kraus and Campbell,
2002; Kraus, 2008). Eradication on that island is now unachievable, which is prob-
lematic because it holds the major portion of Hawaii's large nursery industry
(Kaiser and Burnett, 2006). Consequently, Hawaii Island serves as a source of
repeated frog invasions to the other islands of the archipelago and to extra-territorial
locations. As a result, populations have become established on Kauai, Maui, and
Oahu. Eradication of the few populations known on Kauai and Oahu seems likely
to succeed because they were tackled before they became irremediably large. For
example, all four established populations on Oahu appear close to being eradicated,
with breeding populations now apparently absent and all newly calling animals
(newly maturing males that had been silent as juveniles) immediately treated upon
first detection. Calling animals have not been heard for many months at any of these
sites (S. Williamson, Hawaii Department of Land & Natural Resources, personal
communication, 2007). The sole population on Kauai is not far behind and should
lack a reproducing population by the end of 2007 (K. Gunderson, Kauai Invasive
Species Committee, personal communication, 2007). Programs on both islands
involve frequent surveys for calling animals, clearing of thick vegetation to reduce
habitat, and frequent spraying with citric acid or hydrated lime to kill frogs.
Furthermore, Molokai has successfully avoided infestation due to immediate
